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ОглавлениеCHAPTER 1
CHRYSLER SLANT SIX HISTORY
The Chrysler Slant Six engine concept was a direct result of Chrysler’s desire to enter an emerging compact car market. The Valiant program started in 1957, and Chrysler did not have an engine that was suitable for that type of vehicle. Low vehicle cost and high fuel economy were required; the 277-ci small-block Chrysler V-8 of the time was too large for the compact car’s platform, and its 230-ci L-head (flathead) 6-cylinder engine was outdated with low power and poor fuel efficiency.
The new 1960 Valiant started life as its own brand under the Chrysler Corporation umbrella. This vehicle led to an all-new-design inline 6-cylinder engine that we now know as the Chrysler Slant Six.
Initial Engine Design Work
The new 1960 Valiant had to be a smaller vehicle that could hold up to six passengers, have a reduced frontal area, and be lightweight for improved fuel economy and performance. These requirements would need a short engine with a low profile. Initial Valiant engine concepts included a 150-ci overhead-valve, a cast-iron inline-6, an aluminum V-6 design, and an aluminum inline-6.
170 and 225 ci
An inline-6 engine design with a maximum of 170 ci was preferred by the Chrysler Engine Design department and looked favorable in early design studies. By May 1958, there was a request to have a larger version of the proposed Valiant inline-6 engine design so it could be used to replace the aging 230-ci L-head 6-cylinder in all Chrysler vehicles. The Engine Design team raised the 170’s block deck and added 1 inch of stroke to the concept while using the same bore, cylinder head, and other supporting components. This resulted in a 225-ci engine.
The Slant Six design shows the low position of the oil pump and distributor with both items being driven directly off a gear hobbed into the center of the camshaft. The signature 30-degree slant shows how this idea allowed for a longer runner intake and exhaust manifold while keeping the engine compact and narrow. (Photo Courtesy Bill Weertman)
Large-diameter Chrysler big-block lifters were designed into the new Slant Six. The large crankshaft and its four main bearings are big-block sized. Special attention was given to the position of the water pump and the low-profile harmonic damper. This was done to keep the engine’s length as short as possible. (Photo Courtesy Bill Weertman)
The single-wall thickness between the cylinder bores and the camshaft tunnel was done to keep the engine narrow and to position the camshaft so a Mopar big-block timing chain could be used. This thin wall later became an obstacle to any significant bore size or engine displacement increases to the Slant Six.
The newly developed 170 and 225 inline-6 bore size, spacing, and crankshaft design were all interrelated, and this had the biggest impact on the engine’s overall size and length. A relatively small bore diameter of 3.4 inches and a crankshaft with four main bearings were the result. A large 2.75-inch main bearing size was selected because it was already in use on the 383- and 413-ci Chrysler big-block engines and because the large size was needed to avoid bending and torsional stress problems that were sometimes encountered with a four-main crankshaft in a long-stroke engine. The 2.75-inch main bearing size was overkill for the 170, but it was used anyway in order to standardize the tooling and parts used on both engines.
The desire to standardize parts used in the new inline-6 family is also seen in the cam and cam timing components. The crankshaft’s timing chain gear, the timing chain, and the lifter diameter are the same as the ones used in the Chrysler big-block engines released shortly before the Slant Six. The initial designs used bottom-loading mushroom-style lifters and a higher camshaft location carried over from the L-head 6-cylinder. The possible need to use hydraulic lifters in an aluminum-block engine and to have the lifters load from the top led to the 170’s and 225’s final design. The lifter style and the camshaft’s final location took considerable engineering efforts. Eventually, the Slant Six’s final camshaft location would become a limitation for future displacement increases because the cam’s location is close to the underside of the cylinder bores.
The locations for the fuel pump, distributor, oil pump, and main oil feed gallery were also based on the plan to produce the engine block using an aluminum die-casting process. The decision to locate the oil pump and distributor in the center of the engine block on the camshaft side was due to the desire to drive the oil pump and distributor directly from a single gear hobbed onto the camshaft. This location also kept the branches of the main oil galleries an even length, providing retraction of long oil gallery–forming core pins from an aluminum engine die-casting mold.
The 30-degree slant to the newly designed engine came about as engineers worked to keep the engine as short and low as possible when installed in the new Valiant’s chassis. The idea started with moving the water pump off to one side from the front of the engine. This led to slanting the engine so the water pump’s shaft would stay close to the vehicle’s chassis centerline. The choice was made to tilt the engine to the right to give room for the steering box and steering column shaft. The tilt to the right also allowed room for longer branches on the intake and exhaust manifolds.
A 30-degree angle was selected because it was a reasonable compromise of width, height, and access to the distributor, oil pump, and fuel pump, which were all mounted on the right (underslant) side of the engine. Other angles were reviewed, but, in the end, exactly 30 degrees was selected in order to simplify the design calculations and drafting efforts.
Chrysler Engineering designated the letter “G” for the new Slant Six engine family with G or LG (Low G) being used for the 170 ci and RG (Raised G) used for the 225 ci. A patent was then issued on the engine configuration under the name of the lead engineer Fred Rose.
The Die-Cast Aluminum-Block 225 Program
During the initial design period of the Slant Six engine, the automotive industry had a focus on lighter weight vehicles. This focus pushed the Chrysler Engine Design team to make many design decisions based on the new inline-6 being made of aluminum.
Besides weight savings, there would be machining advantages with aluminum, including reducing machining stock material thicknesses, using higher machine speeds and feeds, and having less tool wear and breakage. Of the methods used for making aluminum parts, high-pressure die casting was considered best for accuracy and for high-volume production. The goal was to design the die-cast engine components so many features could be used as cast without further machining. Where machining was required, material thicknesses were kept to a minimum. The Engine Design team had the view that the new Valiant could have a lightweight aluminum engine with little to no cost penalty compared to a cast-iron engine block.
It was recognized that developing and manufacturing a die-cast aluminum cylinder block and cylinder head involved major risk. At the time, there were no high-volume suppliers for this type of part. As a result, cast-iron versions of the new block and head design were done in parallel. This applied to the 170 and the 225 concept, so Chrysler now had four related inline-6 engines in simultaneous development: 170 and 225, iron and aluminum, with the primary design focus on the two aluminum-block versions. The focus on using the weaker aluminum material resulted in design features that were well beyond requirements when carried over into a cast-iron engine block design.
Cylinder Blocks
The die-cast aluminum cylinder blocks were designed with an open top deck. They used cast-in-place cast-iron cylinder liners that stood 7 inches tall in the water jacket area. The block was extended below the crankshaft’s centerline to add beam structure. The crankshaft was held in place by upper and lower cast-iron main bearing caps to control main bearing oil clearances throughout the engine’s operating temperature range.
The rear main seal also received an upper main seal retainer cap. This was done to simplify the block’s crankshaft pocket machining work. The cylinder head and the main bearing cap bolts used on the aluminum blocks have a longer threaded area to reduce the chance of stripping the threads out of the mating tapped holes in aluminum.
These are the significant differences in the aluminum versus cast-iron cylinder block designs. All other major engine parts were the same in the aluminum and cast-iron block Slant Six engines.
US patent number 3109416 listed the inventors and the filing attorneys. Willem L. Weertman was the chief engineer responsible for this new engine. (Photo Courtesy Bill Weertman)
The new Slant Six was initially designed to be made from aluminum in order to reduce the engine’s weight. Designers also believed that a die-cast aluminum engine block would increase production speed and decrease block machining time and tool wear.
The manifold side of the die-cast aluminum Slant Six engine block shows the lack of freeze plugs and the contours around six individual cylinders. The water pump’s mounting flange location was moved to the side of the block so the engine’s length could be minimized.
The weight savings focus would also find its way into other bolt-on engine component designs. The cylinder head, intake manifold, water pump housing, oil pump housing, and thermostat cover were all designed as die-cast or sandcast aluminum parts.
Changes over the Production Years
The basic Slant Six design and structure (overall dimensions, bolt patterns, etc.) went unchanged during its 31-year production history. This means a cylinder head, manifold, oil pan, and other parts from a 1960 170 Slant Six will bolt onto a 225 engine produced in 1987. With that said, there were continual internal and external changes being made to improve and refine the engine during its production run.
A list of major events and basic changes made to the engine follows. This is by no means a complete list covering all the Slant Six engine variations developed for different applications, chassis, and markets, but it can be used as a general guide for the enthusiast looking for the best Slant Six engine for their intended use.
| 170- and 225-ci Internal and External Changes | |
| 1960 | Start of production for cast-iron 170-ci and 225-ci engines. |
| 1961 | Production release of 225-ci aluminum-block engines. Intake manifolds changed from aluminum to cast iron. Alternator moved from left side to right side of engine. Last year of the Hyper-Pak engine option. A 225-ci engine was added to the Valiant as an option. |
| 1963 | Last year of the aluminum 225-ci engine. PCV valve used on all Slant Six engines. |
| 1964 | Created a 100-percent closed crankcase vent system in California. |
| 1967 | A 2-barrel intake manifold and carburetor setup is offered for export engines. Cylinder head combustion chamber shape is modified for improved combustion. |
| 1968 | Crankshaft rear flange counterbore size increased. Closed crankcase venting on all engines. |
| 1969 | Last year of 170-ci engine availability for US and Canada market. |
| 1970 | Start of 198-ci engine production. |
| 1972 | Exhaust valve seats are induction hardened. Air injection added to California engines. |
| 1973 | EGR valve added. |
| 1974 | The last year of 198-ci engine production. |
| 1975 | New cylinder head: taper-seat spark plugs with no plug tubes. |
| 1976 | General weight reduction. Aluminum intake manifold for Feather Duster/Dart Light. Forged-steel crankshaft changed to nodular cast iron in mid-1976 production. |
| 1977 | A 2-barrel intake and carb option added to domestic engines. |
| 1978 | Intake manifold changed from cast iron to aluminum. |
| 1981 | Hydraulic lifters introduced that had nonadjustable rocker arms and a wide valve cover. |
| 1983 | Last year of domestic passenger car Slant Six engine use. |
| 1984 | Last year of Slant Six engine production at the Trenton Engine Plant. Additional weight reduction on the cast-iron crankshaft. |
| 1987 | Last year of Slant Six engine use in domestic trucks. |
| 1991 | Last year of Slant Six engine production at the Toluca, Mexico, engine plant. |
Engine Identification
There are five basic Slant Six engine cylinder block types that were released into production. Four are made of cast iron and one is an aluminum die casting. The different cast-iron blocks produced can make it confusing when you’re trying to figure out exactly which engine you have in your vehicle or which engine you spotted at a swap meet or in a wrecking yard.
Slant Six engine blocks can all look the same at a distance, but there were actually five different block types used over the years.
The engine block’s casting number is located on the driver’s side of the block. The engine’s build numbers are stamped into a pad on the front passenger’s side of the block’s head gasket surface. These numbers are the best way to identify the engine and the production date, but the casting and stamped-in numbers can sometimes be missing or misleading. Besides the numbers, there are other easy-to-spot engine block features that can help you quickly identify a Slant Six.
170-ci Cast Iron (1960–1969)
Low-deck 170-ci cast-iron block Slant Six engines (LG designation) with forged-steel crankshafts (FC) were built between 1960 and 1969. All of the 170 engines used forged cranks with a 3.125-inch stroke. The distance between the top head gasket surface and the crankshaft centerline (deck height) is 9.06 inches. The 170 block casting number was 2463230, and that number was located on the driver’s side of the block.
All 170-ci blocks had three freeze plugs, with the center plug being 2.25 inches higher than the outer two.
Revell Quarter-Scale Slant Six Model Kit Story
by Steve Magnante
with Willem “Bill” Weertman
S ince most car enthusiasts caught the automotive bug early in life, thanks to plastic model kits, it seemed appropriate to review one of the most interesting and complex plastic model kits in history: Revell’s quarter-scale Slant Six engine and transmission.
Bill Weertman worked directly with Revell to ensure that the 1/4-scale model of the Slant Six was as accurate as possible. (All Photos Courtesy Steve Magnante)
Introduced in the fall of 1961 and produced for about two years, Revell kit number H-1553:1295 cost a hefty $12.95 when it was new. At that time, a typical 1/25-scale car model kit was priced at well under two bucks. Thanks to its incredible realism, the Revell engine kit required an advanced level of skill. Mixing those two things together (high cost and the need to get Dad involved), the Revell kit wasn’t a huge success. The one thing that saved it from likely oblivion was Chrysler Corporation’s direct involvement in the project. That meant the full weight of Chrysler’s public relations and marketing departments was called upon to spread the word. As a result, Chrysler sponsored full-page ads promoting the kit in magazines ranging from Hot Rod to Life and even nudged magazine editors to publish new product alerts and actual editorial stories, including the one that appeared in the September 1961 issue of Rod & Custom magazine.
Even if it wasn’t a hobby shop sales record setter, the Revell Slant Six model kit got first-class exposure that continues here in Doug Dutra’s much-needed Slant Six book. Let’s explore a vintage Revell Slant Six kit that was purchased on eBay. If you search “revell slant six” online, you’ll see the impact left by this great Revell model kit.
We reached out to Willem Weertman for his memories about the Rev-ell Slant Six model kit program, and he shared some amazing memories. If Weertman’s name isn’t immediately familiar, know that he was Chrysler’s assistant chief engineer during the Slant Six and Chrysler Street Hemi development programs.
If you’ve ever read the iconic “Hemi White Paper” article in the August 1966 issue of Hot Rod magazine, you’ll recognize Weertman’s face and his informative yet personable writing style. As a Chrysler employee, he worked directly with the Revell modelers as the liaison between them and Chrysler engineering. The following is Bill’s commentary on his part in developing the Revell Slant Six model kit:
“The Revell Slant Six model kit had an interesting start. Sometime after production of the Slant Six engine began and the engine was a fresh newcomer on the automotive scene, an executive of Chrysler corporate advertising and a public relations executive of Revell, Inc., a company well known for its accurate scale models, especially of ships, happened to meet at an advertising industry function (reportedly a hospitality party). In talking about their respective products, the idea was hatched between the two executives for Revell, with technical support from Chrysler, to make a scale model of the Slant Six engine.
“It would not simply be a static model of the exterior of the engine but a model with all the parts, which could actually be motored to show internal parts in motion. That would give the builders of the model quite an education in the workings of an automotive engine as well an introduction to a distinctive Chrysler product.
“The Chrysler advertising executive secured the cooperation of the top Chrysler engineering executives. In early 1960, as managing engineer of the Engine Design Department, I was asked to send Revell whatever it needed for the project. On April 20, 1960, we sent a complete set of drawings of the 170-ci Slant Six engine so they could start work on a 1/4-size scale model of the engine. In addition to the drawings, I think they were also furnished an actual engine assembly.
“Over the next several months, I would occasionally receive inquiries by phone from my Revell contact, their chief engineer. By February 1961, Revell had a prototype of the engine model kit ready to show to distributors and dealers that would be attending the annual weeklong Hobby Industry Trade Show in Chicago. For the Revell booth at the show, Chrysler shipped one of its own cutaway, motor-driven Slant Six display engines. I was asked to give a short, private talk about the engine to the Revell people who were there for the show and to attend the booth along with the Revell staff to answer questions about the engine. I helped man the booth and found the Revell group to be very friendly and interesting; we got along just fine.
“Revell sent me one of the very first pilot production kits with a request that I assemble the engine and send back any comments I might have. Well, I made the assembly with some judicious filing and sanding to get the plastic parts to fit together properly and then found the engine looked okay but had so much friction that the small battery-driven electric motor didn’t have a chance to put the internal parts in motion. So I made a complete disassembly followed by additional filing and sanding for running clearance improvement and then a reassembly. This time success. The engine came alive with the crankshaft rotating, the pistons going up and down, valves opening and closing, and the miniature lightbulbs representing spark plugs turning on and off in the correct sequence. Wow!
“Revell had very skillfully designed the model so that when the removable pieces that included the intake and exhaust manifolds and the left side of the cylinder head and the left side of the cylinder block were lifted away, the internal action was exposed for viewing. I sent Revell a detailed report on my experience assembling the engine. I don’t know if any revisions were made to the engine parts before high-volume production began. Years later, I gave my assembled model to the Chrysler archives.
“Full production of the model engine started in the fall of 1961, in time for the Christmas-buying season. In addition to assembly instructions, each boxed kit had an eight-page booklet describing the basic workings of an internal combustion engine, reinforcing the educational aspect of the model.
“After sales started, quite a few letters arrived on my desk from model builders all over the country with complimentary comments and interest in additional information about Chrysler engines. I continued communicating with Revell, sending them engineering drawings of possible future changes to the Slant Six engine, including the aluminum cylinder block version and the change in crankcase ventilation from the original road draft tube to the positive crankcase ventilation system that was used 100 percent in 1963 after being a California-only requirement in 1961 and 1962. There was some consideration for their updating the model to reflect production changes made to the real engine. However, as far as I know nothing ever came of this, and to the best of my knowledge the model was unchanged during its production run. For me it was a fun project with lasting good memories and a nice bit of personal recognition.”
—Bill Weertman, July 6, 2007
The assembled model measures 14¾ inches from fan blade to tail shaft and about 7 inches from oil pan to air cleaner. While most assume the kit is based on a 225-ci Slant Six, Weertman tells us it is actually based on the low-deck 170-ci Slant Six. The massive box measures 22×14¾ and is 3 inches deep.
An eight-page educational booklet on how an internal combustion engine works was included in the Revell Slant Six model kits.
The assembled model is shown on the stand provided. The kits we found came with the original box.
There are no fewer than four shades of plastic: red, silver, gray, and black. They are used in the kit to reduce the need for painting. Full-color decals adorn the air and oil filters as well as the display stand.
Cleverly hidden inside the beautifully rendered A903 3-speed manual transmission lurks a small battery-operated electric motor that turns the crank, rods, pistons, rocker arms, and valves when the power button is pushed.
Four small screws secure the transmission to the bellhousing. The beauty of the Revell Slant Six model is that it can be disassembled and rebuilt time and time again. The intake and exhaust tract simply snaps into the side of the cylinder head, and nuts and screws hold the rest of the kit’s approximately 300 parts together. The entire driver-side wall of the block is removable to expose the cylinder bores and pistons.
The following photos show the intricate details contained in this model kit. One example is the completely flat valve cover, a characteristic of the 1960-only 170-ci Slant Six, which the kit was designed from. ■
A slotted drive coupler inside the bellhousing plugs into the motorized “transmission.”
Many pieces can be removed to show cutaway details on internal parts.
The piston rings were made in different colors of plastic: red for compression rings and green for the oil control rings.
The detailed cylinder head even bears a casting number (21214764), correct for a 1960 cast-iron Slant Six. Note the detailed rocker arm shafts, valve springs, and rocker arms. This is just like the real thing.
All of the parts in this exploded view can be snapped back in place within a matter of seconds. Tiny metal screws secure the valve cover and oil pan. Dig the correct unsilenced air cleaner; only the front half of the filter was shielded from water mist. Fully enclosed air cleaner lids arrived in 1962.
The combustion chamber and valve head detail is totally accurate. The intake and exhaust port floors are cast integrally with the intake and exhaust manifold segment. Check out the tiny screws attaching the bellhousing to the block.
This shot gives an idea of how large this model is. The valves move smoothly in the guides, and the metal valve springs still have good tension, even after being on display for decades.
Yep, there are even individual lifters and pushrods inside the engine.
The main caps are held down by metal bolts while real nut and screw fasteners secure the rod caps. The crankshaft is also shaped and contoured just like a forged-steel production piece and even has the rough finish on the counterweights.
The bottom of the box features a complete parts inventory list with photos of every item. The two kits purchased got us far, but we still have not seen an original instruction sheet nor have we seen the original Revell battery box that came with the kit.
The September 1961 issue of Rod & Custom contained a full-page look-see story on the kit. The article states that more than 15,000 man-hours and a quarter of a million dollars went into the development of this 300-piece model kit. We believe it!
The cylinder block’s casting number is located on the manifold side of the engine block below the freeze plugs. The dash number shown after the seven-digit casting number relates to the casting patterns used to make that block.
The engine build stamping is often missing on replacement engine blocks or blocks that have been rebuilt. These stamped numbers get machined away if you resurface the block’s deck surface. Copy down your engine’s markings before you deck the block, then restamp as needed.
Block deck resurfacing can erase the stamped build numbers, and casting flaws can make the casting numbers hard to read or confusing. This five–freeze plug 225 engine block should carry casting number 2806830, but it is missing the second 8.
All 170-ci Slant Six engine blocks carry casting number 2463230-XX. The 170 has a zero-deck height, which means the pistons come to the top of the cylinder bores. This 170 block casting number is followed by a “-1”, which is the reference to the casting equipment used to make the block. Other markings include a date code and the production shift that produced the casting. This block also carries a rebuilder’s ID tag that was added when the engine was rebuilt.
All 170 Slant Six engine blocks have three freeze plugs, with the center plug positioned higher than the outer two freeze plugs. All 170 engines used forged-steel crankshafts, so the gusset behind the water pump is tapered.
The 170-ci engine block had a shorter height, so the assembled engine sat lower in the vehicle’s engine compartment. To the trained eye, the bare block appeared shorter, but the easy-to-spot feature was the shorter (1.75-inch) coolant bypass hose between the cylinder head and the water pump. The other tip was the 1×3/4×5/8-inch-thick cast-in rectangle at the top of the driver’s side of the cylinder deck. On the low-deck 170, this rectangle sits directly on the water pump’s mounting flange.
The 170-ci engine block was shorter, so the short coolant bypass hose is an easy way to identify a 170 Slant Six. All 170 engines have forged-steel crankshafts and carry casting number 2463230.
A 170 Slant Six engine block is shorter than a 225 or 198 block. Look at the area where the water pump meets the top deck and head gasket surface as a way to spot the difference.
225-ci Cast Iron (1960–1967)
The high-deck 225 cast-iron block Slant Six (RG designation) with a forged-steel crank (RGFC) had a 10.70-inch deck height and a 4.125-inch stroke. The forged crankshaft Slant Six engine blocks were produced in two distinct castings. An early three-freeze plug version (with the center plug being 2.25 inches higher than the outer two) was produced between 1960 and 1967. The early 225 block casting number was 2463430, and it was located on the driver’s side of the block.
A side-by-side comparison between a 170 and a 225 engine block shows how much shorter a 170 Slant Six engine block is.
198- and 225-ci RGFC (1968–1976)
The later RGFC block with casting number 2806830 was produced between 1968 and 1976. This block type was used to build both 198- and 225-ci Slant Six engines. RGFC blocks had five freeze plugs all in a row with all at the same height.
The easily spotted feature for the RG-type engine blocks was the longer (3.75-inch) coolant bypass hose between the cylinder head and the water pump. Also, the 1×3/4×5/8-inch-thick cast rectangle at the top of the deck had a 1.5-inch space between it and the water pump’s mounting flange.
The BH-type blocks that have extra ribs on the water jacket side of the block were produced as part of this production series of 225 RGFC engines.
225-ci RG (1976–1991)
The last major cylinder block type produced was the high-deck (RG) cast-iron block with the nodular cast-iron crankshaft (RGCC). These RGCC blocks were produced from the middle of 1976-model production through the end of the Slant Six production run. Most carried engine block casting number 330 or 530 on the driver’s side of the block.
RGCC blocks had five freeze plugs at the same height and the same coolant bypass hose and cast-in rectangle spacing as noted above. Cast-crank SL6 engines have the capital letter “E” stamped into the ID pad, after the displacement number (225E). The easy-to-spot feature for the RGCC engine block was the thickness of the cast-in gusset behind the water pump’s mounting flange. On cast-iron crankshaft engine blocks, this gusset is a uniform 5/16 inch, straight across the back of the water pump flange. This gusset tapers from 3/8 inch up to 3/4-inch thickness on all forged crankshaft Slant Six engine blocks, with the only exception being the 1976 “030” RGFC block casting.
The driver’s side of an early raised-block 225 with three freeze plugs has casting number 2463430. The center freeze plug is located higher than the outer two, and the gusset behind the water pump is tapered. All these blocks came with a forged-steel crankshaft.
The later-raised Slant Six engine block has five freeze plugs and came with forged-steel or cast-iron crankshafts. The forged-steel crankshaft block carries casting number 2806830 and was also used to build 198-ci Slant Six engines.
Looking at the coolant bypass hose is the fastest way to see if the engine is a low-block 170 or a tall-block 225 or 198. The tall block has the 3.5-inch-long hose as shown; low-block engines have about a 1.5-inch hose.
There is a 1.5-inch space between the water pump’s mounting flange and the rectangular casting lump on 225 and 198 engine blocks.
The tapered horizontal rib or gusset behind the water pump mounting indicates that this block has a forged-steel crankshaft. “BH” blocks have two extra pencil-shaped ribs running top to bottom, in front and behind the row of freeze plugs.
BH engine blocks have extra ribs in front and behind the row of five freeze plugs. In general, the 1968–1975 RGFC blocks show higher casting quality compared to the earlier three–freeze plug block with the BH blocks being sought after for high-performance and race engine buildups.
The thinner and straight horizontal rib, or gusset, behind the water pump mounting flange indicates that this five–freeze plug RG engine block has a nodular cast-iron crankshaft.
225-ci Aluminum
The die-cast aluminum-block 225 Slant Six had a high deck and used the forged-steel crankshaft (ALFC). The aluminum-block Slant Six is different from all the other cast-iron block engines. There were 50,000 engines produced from 1961 to early 1963 model years, using a state-of-the-art high-pressure die-casting process.
The aluminum block had cast-in-place iron cylinder sleeves, used two-piece (top and bottom) cast-iron main cap inserts with longer main cap bolts, and did not use cam bearing inserts (the camshaft journals rode directly on the aluminum block).
The aluminum block had an open-top deck design with the head gasket’s fire ring sealing on the tops of the freestanding cast-iron cylinder bore sleeves. Longer and deeper threaded head bolt holes and longer head bolts are used to get the needed clamping force on the head gasket. The aluminum block carried casting number 2121355 on the driver’s side, and a magnet will not stick to this block.
The fastest way to identify one of the rare Slant Six aluminum blocks is to look for freeze plugs. All of the cast-iron Slant Six engine blocks had freeze plugs along the driver’s side of the block, but the aluminum-block engine had no freeze plugs. The aluminum Slant Six was approximately 75 pounds lighter, but it was not nearly as strong as its cast-iron siblings. It is more difficult to rebuild as well. For these reasons, we will focus our attention on the more commonly found “bulletproof” cast-iron Slant Sixes.
Casting Numbers
Most Chrysler casting numbers of this era are seven digits long followed by a dash number. The number after the dash identifies the casting pattern equipment used to mold a specific part. There are also some letters and other markings that identify the foundry that made the casting and the shift that produced it. These markings include the numbers 1, 2, and 3; “D” for the day shift; and “N” for the night shift.
The Slant Six engine block casting numbers can identify a range of production years. They also identify the crankshaft type: forged steel or cast iron. The engine size, manufacturing year, and date code are also stamped into a pad, which we will discuss in detail later in this book.
The die-cast aluminum Slant Six engine block has its casting number on a small medallion on the manifold side of the block. The last three numbers on this block casting are less defined than the “2121” that proceeds them.
VIN Stamping
The vehicle identification number (VIN) was stamped onto the Slant Six engine block starting in 1968. The VIN (or part of it) is stamped into a machined pad on the passenger’s side along the lifter gallery toward the rear of the block. This pad is facing the fenderwell, so it is hard to read when the engine is installed. Use a mirror or view it from underneath the vehicle.
All forged-steel Slant Six crankshafts use the same crankshaft bearing inserts, so any forged-steel Slant Six crankshaft will fit into any Slant Six engine block made for a forged-steel crank. The only exception to this rule is trying to install a long-stroke 225 crankshaft into a short-stroke 170 engine block. The longer throws on the 225 crankshaft interfere with the smaller crankshaft pocket area found in the 170 engine block.
Likewise, any cast-iron Slant Six crankshaft will swap into any cast crank Slant Six engine block. This is important because a lightweight cast crank was offered late in the Slant Six production run (1984 to the end of production). A fast way to identify a cast crankshaft Slant Six engine block is to look at the gusset thickness on the back of the water pump’s mounting flange or inspect the crankshaft or its bearings.
The early engine block stampings have a letter to define the year and the first two numbers of the displacement followed by a build sequence code. “V22” indicates a 225-ci 1964-model engine.
Decoding Engine Block ID Stampings
By Daniel Stern (aka SlantSixDan)
Identifying a Slant Six engine (or engine block) requires finding and understanding the block casting number and the engine ID code. The ID code was stamped on the block at the final stage of manufacture. These “what, when, and where” block stamping numbers will indicate some or all of the following:
• Vehicle model year the engine was originally built for
• Cubic inch displacement of the engine
• Whether the engine was built for a car or truck/van
• Where the engine was built (production plant)
• Engine build date (month and day)
• Gasoline type the engine was designed to run on (regular or premium)
• Nonstandard-size parts in the engine (if any)
The stamping code format changed over the years, and there are some “gotchas” in the system. The assembly plants sometimes deviated from the official Chrysler Corporation format, and it’s not uncommon to find carelessly or improperly stamped engines. Decoding the stamping, piece by piece, even in accord with the correct-year parts and service manuals, won’t necessarily tell you what you’re looking at. You’ll sometimes have to use other clues to confirm or correct what the stamping says.
Where’s the Code?
To decode the stamping, you have to find it. On most Slant Six engines, it’s on a 1/4-inch protruding ledge of the deck surface located on the distributor side of the block, outboard of the front (number-1) cylinder, and facing the sky. This puts the stamping below the front spark plug on an assembled engine, behind and below the alternator, inboard of the ignition coil, in the most common Slant Six engine configuration. This ledge usually gets crudded up with grease and dirt over the years, so you may have to scrape and wipe the area clean to reveal the stamping.
Exceptions are first-year (1960) engines that are stamped elsewhere, often in a similar location but at the rear instead of at the front or behind the water pump. Late-production engines (1980s) may also be stamped on the passenger-side edge near the rear cylinder.
Starting in 1968, the VIN legally had to be stamped into the engine block. The Slant Six used a machined pad located at the rear of the lifter gallery rail.
A close-up view of a vehicle identification number (VIN). If this is your vehicle’s VIN number, I have the original Slant Six engine block out of it!
First in the stamping sequence is the vehicle model year that the engine was originally built for. Through 1973, this was encoded with a letter, as shown on page 23.
The letters aren’t fully sequential; we jump from V for 1964 to A for 1965, and the letters U and I are not used. The letter Q is also not used in engine stampings, which is a bit of a “gotcha” because these year letters were also used to designate the cars themselves (“R series” for 1961, “S series” for 1962, etc.). For some reason, Chrysler designated all 1960 models as P-series cars except the 1960 Valiant, which it called a Q-series, yet 1960 Valiant engines have P-code date stamps.
Starting in 1974, the letter identification system went away, and the last digit of the model year was used instead: 4 for 1974, 5 for 1975, 6 for 1976, and so on. By the early 1980s, Chrysler Corporation was a disorganized mess, and the chaos even extended to engine stampings. Some plants carried on using the last digit of the model year, while others used letters of one kind or another. Fortunately, by that time there were usually other clues to help sort out what you’re looking at. Sometimes it’s unclear until you cross-reference the stamping with the block’s casting number (or lack of numbers) to narrow down the range of possibility.
Displacement Stamping
After the model year comes the engine displacement, or “what” number(s). Only the first two digits of the displacement were used through 1964, so 17 for a 170-ci engine or 22 for a 225. Starting in 1965, the entire displacement was stamped: 170 or 225 through 1969, 198 or 225 from 1970 to 1974, and just 225 starting in 1975.
Before we get to the when-and-where part of the stamping, we need to consider some additional gotcha points, in the form of extra letters and letters that mean more than one thing. From 1961 to 1963, Chrysler built about 50,000 aluminum-block 225 engines. These had an A (for aluminum) after the model year in the stamping, so RA 22 for a 1961 engine, SA 22 for a 1962, and TA 22 for a 1963 aluminum-block Slant Six. The letter A also means 1965, and T also means a truck engine, so TA 22 means a 1963 aluminum 225 passenger-car engine, but AT 225 means an iron-block 225 built for a 1965-model truck.
The Slant Six engine manufacturing information stamping is commonly found on the passenger’s side of the block, under the number-1 spark plug.
Model Year Stamping Codes
| Model Year | Code |
| I960 | P |
| 1961 | R |
| 1962 | S |
| 1963 | T |
| 1964 | V |
| 1965 | A |
| 1966 | B |
| 1967 | C |
| 1968 | D |
| 1969 | E |
| 1970 | F |
| 1971 | G |
| 1972 | H |
| 1973 | J |
The when and where parts of the stamping come next. Two different systems were used for indicating when the engine was assembled. Starting in 1960, it was a simple month-day stamping: 8 2 means August 2; 10 17 means October 17; 5 5 means May 5; and so on. Here’s another gotcha point: remember we’re talking about model years, not calendar years. The changeover from the current model to the next year’s model was in September, so take care to decode the month and day correctly, in accord with the letter indicating the model year: a month indicator of 9, 10, 11, or 12 means September, October, November, or December of the calendar year before the indicated model year.
This is where most pre-1968 engine stampings stop providing useful information. Extra numbers such as -2 or -3 were internal production line or shift codes that were used at the factory for keeping track of which engines came off which line. They aren’t meaningful for engine identification in the field.
Let’s look at a few samples of early engine stampings:
Q 17 7 13 is a 1960 Valiant 170 engine assembled on July 13, 1960.
P 22 10 4 is a 1960 Plymouth/Dodge 225 engine assembled on October 4, 1959 (model year!).
S 22 6 12 is a 1962 iron-block 225 engine assembled on June 12, 1962.
SA 22 6 12 is a 1962 aluminum-block 225 engine assembled on June 12, 1962.
V 17 11 17 is a 1964 170 engine assembled on November 17, 1963 (model year!).
B 225 3 7 is a 1966 225 engine assembled on March 7, 1966.
TA 22 4 9 is a 1963 aluminum-block 225 engine assembled on April 9, 1963.
AT 225 4 9 is a 1965 225 truck engine assembled on April 9, 1965.
Now for more “gotcha” points: With this system it’s easy to have what looks like a stamping that conflicts with itself. For example, how about A 170 2 25? That’s got both “170” and “225” in it, and due to random spacing it’s entirely possible it would appear as A 170 225, but remember the stamping code order of year, displacement, date to figure out that this is a 1965 170 engine assembled on February 25, 1965.
10,000-Day Calendar
Chrysler started using a 10,000-day calendar on July 29, 1961. That date was indicated by a code of 0001. The following day (July 30, 1961) was 0002, and so on. It’s easy to find a decoder for this calendar by doing an Internet search for “Chrysler 10,000 day calendar.” You can then enter a code and find out what date it means.
The gotcha is this kind of date code was applied on engines starting for the 1968 model year, but some plants switched over several years earlier, and some plants hung on to the old way for quite a few years. If you see an engine stamped V 22 10 92, that’s a sure sign you’re looking at the new-type date code rather than an old-type code because there’s no such date as October 92. Put 1092 into an online decoder and it tells you that means July 24, 1964.
But what if you’re faced with V 22 11 07? A plain reading gives November 7, 1963 (remember we’re talking about model years), which is valid. Plugging it in the online 10,000-day calendar gives August 8, 1964, which is an equally valid date. In a case like this, you’ll have to either use other clues, such as the build date of the engine’s original vehicle if you can find it out, or let it remain a somewhat mysterious 1964 engine.
Engine Plant Stamping 1968 and Beyond
Officially there was no provision for the “where” in 1967 or earlier engine stampings; the engine plant wasn’t indicated. Starting in 1968, the engine plant was sometimes indicated with T or PT for Trenton, Michigan; M or PM for Mound Road, Michigan; and W or PW for Windsor, Canada. Alternatively, sometimes engines built at the Windsor engine plant had a C prefix. And look, it’s that pesky letter T again, which now has three meanings to keep track of: 1963 model year, truck engine, and Trenton engine plant. Later on, K or PK was added to mean the engine plant at Toluca, Mexico.
In addition, in the middle of the 1976 model year the crankshaft on the Slant Six was changed from forged steel to cast iron, as detailed elsewhere in this book. Cast-crank engines have an E in their stamping, adding a second meaning to that letter besides 1969.
Here are some sample stampings that might be found on engines made for 1968 or later passenger cars and trucks:
3W225 4326 decodes as follows:
3 = 1973 model year
W = Windsor engine plant
225 = Engine displacement
43 26 = June 1, 1973
(on the 10,000-day calendar)
CG198 3434 decodes as follows:
C = Windsor engine plant
(C for Canada)
G = 1971 model year
198 = Engine displacement
3434 = December 22, 1970
(on the 10,000-day calendar)
F225R 7 6 decodes as follows:
F = 1970 model year
225 = Engine displacement
R = Regular-fuel engine
7 6 = July 6, 1970
(old-style date stamp)
E225T 2789 contains a gotcha:
E = 1969 model year
225 = Engine displacement
T = Truck engine or Trenton engine plant (gotcha!)
2789 = March 17, 1969
(on the 10,000-day calendar)
7M225E 5555 decodes as follows:
7 = 1977 model year
M = Mound Road engine plant
225 = Engine displacement
E = Cast-iron crankshaft
5555 = October 12, 1976
(on the 10,000-day calendar)
As the 1970s and 1980s progressed, some engine plants seemed to drift randomly between using month-day dates and using date codes from the 10,000-day calendar. You might find production line/shift codes of up to four digits before or after the date code. It’s best to think about all the possible meanings of the stamped number you are reviewing, including the results of putting any four-digit codes into the online 10,000-day calendar. With that information, it’s usually possible to discard the meanings that don’t make sense and narrow in on the correct identification for the engine you’re looking at.
ID Stamping
The ID stamping location was also used for additional indicator markings. For a time in the 1960s and 1970s, there were three ruggedness levels of the Slant Six engine in trucks and vans: the 225-1 was similar to the passenger-car engine, the 225-2 had some heavy-duty parts, and the 225-3 had even more heavy-duty parts. If you find an engine stamped 225-1, 225-2, or 225-3, that’s what it refers to.
Although all Slant Six engines were built to run on regular gasoline, Chrysler sometimes stamped engines (6- and 8-cylinder alike) configured for regular gasoline or built for passenger car usage with R. This added a second and third meaning to that letter besides 1961. Passenger car engines could also be indicated by PC, while premium-fuel engines could be indicated with P (adding a second meaning to P besides 1960, except for the Valiant).
After the what-when-where information, there will sometimes be a how. If the engine was originally built with nonstandard-size parts, that will be indicated (at least in theory) with characters in the stamping. For instance, an engine originally built with oversize tappets may have a diamond symbol. An engine built with one or more 0.001-inch undersize main or connecting rod bearings is supposed to be indicated by a Maltese cross symbol in the engine stamping (another stamping on the crankshaft tells which one), and a Maltese cross followed by an X indicates the engine was built with all 0.010-inch undersize rod and/or main bearings. Similarly, A can mean one or more oversize cylinder bores (another meaning besides 1965), and X can mean nonstandard valve guides (another meaning besides the one that goes with the Maltese cross). This isn’t likely to be useful information many years after the engine was first built because any rebuild will involve careful measurement to determine the right bearing sizes, valve guides, and cylinder bores.
An example of a Maltese cross is shown on this identification pad stamping. Can you decode the rest of the information?
Random Markings and Stampings
Other markings sometimes found on 1980s engines include HP for a high-performance version and S for an undefined “special” version. Another marking seldom seen on engines built in the United States, Canada, Australia, or South Africa is LC, which indicates the engine was built with low-compression pistons. Those engines were exported to countries where the gasoline had a very low octane rating.
There are some other possibilities for what you might find on the engine ID pad. Numbers that make no sense in terms of the systems described here might be a partial VIN, a date that doesn’t comport with anything else about the engine, or numbers that look random. You might find all or part of the words SERVICE or WARRANTY. These are usually cases where an engine was replaced by a dealer service department, especially if it happened under warranty. You may find the stamping pad completely blank. This can also indicate a replacement engine because new engines and blocks came from Chrysler with nothing stamped on the pad, or it can mean the original stamping has been obliterated by block deck resurfacing or during a car theft (thieves would sometimes weld up and reface the stamping pad to thwart identification of stolen vehicles).
Factory Engine Paint
If all else fails and you’re stuck trying to identify an engine with an absent, illegible, or nonsensical stamping, you can sometimes gain a bit of insight if you can figure out what color the engine was originally painted. It’s not a sure thing, but it can be helpful if it’s all you have. Here’s a guide:
Metallic dark turquoise: 225 engines in 1960–1961 Plymouth and Dodge cars, North American market
Silver: 225 engines in some 1961 Valiant and Lancer cars in the US market, and RV1-series 1962 Valiants in Australia
Red: All 1962–1968 170 and 225 engines in passenger cars in all markets except as below, plus 170 engines in all 1960 and most 1961 Valiant/Lancer cars and 1961–1962 trucks in the US market
Light turquoise: 170 and 225 engines in 1969 passenger cars and trucks in the US market, 170 engines in 1962–1966 Canadian-built Valiants, and 1967–1969 225 engines with 2-barrel carburetion in the Australian market
Blue: 198 and 225 engines in 1970–1983 passenger cars and trucks in the North American market
Orange: 1967 and up 225 engines with 2-barrel carburetion, South African market
Yellow: 225 engines in 1962–1968 trucks/vans/buses, North American market
Black: 1984 and up 225 engines in all applications, North American market
The information presented here applies to engines built for the US market. It also applies to Canadian-market engines starting in 1966 when the Auto Pact integrated the US and Canadian markets for vehicles and parts. Markings on pre-1966 Canadian engines and on Australian, Mexican, Turkish, South African, Spanish, and Swiss engines are likely to differ from what is described here. No matter what country you’re in, if you’re faced with a block stamping that defies decoding with this information, ask an expert. As this book goes to print, most of the world’s Slant Six owners and experts can be found on the Internet, in the forums at slantsix.org and others based in Australia, South Africa, Spain, Mexico, and elsewhere around the world.
