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CHAPTER 2

PREPARING FOR THE REBUILD

When Pontiac designed its V-8 packages, each engine type was subjected to an endurance test, which consisted of static operation at 4,500 rpm on a dynamometer for 100 consecutive hours without shutdown. The engine was then completely disassembled and inspected for any signs of abnormal wear. If nothing of significance was detected, it was one step closer to reaching production.

An engine dynamometer is an excellent tool for breaking in an engine and measuring output under full-throttle load. The best machine shops or engine builders use a dyno to ensure a completely assembled engine operates properly before delivering it to a customer. Measured output values can tell you if your engine meets your performance expectations.

Through durability testing, Pontiac’s goal was to develop a V-8 engine that could endure 100,000 miles of normal use before requiring a rebuild. Extra material was cast into the components so that each could easily accommodate being moderately machined at least once.

Modern passenger car engines are designed to last 150,000 miles or more, and there are a number of factors that allow it to accomplish this. Modern machining and finishing techniques, piston ring technology, and engine oil quality are generally considered better than ever before. Modern fuel injection ensures instant start-up and improved coldweather operation and prevents excessive fueling to wash the oil film from the cylinder walls.

In addition to those advancements, most modern cars are typically lighter and can accelerate with less resistance to motion, lessening the overall load an engine sees on a daily basis. The use of overdrive transmissions equates into reduced engine RPM during normal conditions. Even without these advantages, but with routine maintenance and general care, it’s common to find a Pontiac V-8 that exceeded the 100,000-mile mark by many thousands of miles.

Any engine may require a rebuild for any number of reasons, even one that had a rebuild recently performed. Abnormal thrust bearing wear is evident in this particular Pontiac engine, which might indicate improper bearing main cap alignment or insufficient thrust clearance. In either instance, it requires a rebuild.

Rebuild Basics

Neglect often results in an engine that falls well short of its intended lifetime. There’s no telling what type of lifestyle your Pontiac led prior to your taking possession of it. If your Pontiac V-8 operates smoothly, doesn’t use oil, and doesn’t smoke, chances are that it’s in relatively good operating condition. But it may not be in perfect health and may benefit from a complete rebuild.

The newest Pontiac V-8 was produced in 1981, so it’s quite possible that your engine has already been rebuilt at some point in its life, but there’s also a chance that it’s never been apart before. There’s no way of knowing an engine’s internal condition without complete disassembly, and unless you’ve owned it for a number of years, you really have no way of verifying originality. No matter your engine’s circumstances, now might be the opportune time to give your Pontiac a complete refresh.

When looking for an engine to rebuild, you can tell that an engine has been rebuilt if it has been freshly painted and is relatively free of heavy grease deposits. I prefer an engine that is completely covered in grime because it generally indicates it is a complete original that hasn’t been tampered with over the years. This particular 1966 389 4-barrel could be an excellent foundation for a restoration application.

The purpose of any engine rebuild is to eliminate the internal wear that results from normal operation and restore any lost performance. A typical rebuild should include machining each contact surface, replacing all sacrificial components, and installing new bearings, seals, and gaskets. If properly executed, the effort should produce a Pontiac that runs at least as well as the day it rolled off the assembly line, and the use of high-quality gaskets and seals should prevent any annoying oil or coolant leaks.

There are other factors beyond normal wear that might force an owner to rebuild an engine. Those might include incorrect assembly by a shop during a prior rebuild, significant damage from component failure after exceeding the engine’s intended operating range, or simply bad luck. The machining performed during the rebuilds, or the extent of damage that occurred when a component let go, determines how useable your existing components are.

Creating a Plan

One of the first steps to any successful rebuild is creating a sound plan of action. You need to determine which category your rebuild best falls within. Is your engine a strictly stock rebuild, a mildly modified street engine, a significantly modified street/strip setup, or something in between the previous descriptions? After you’ve identified the type of engine you want and the application for the engine, you need to establish a fairly certain horsepower and torque target. This helps you and a machinist select the parts to meet your goal and then establish the budget for build project.

Each type of rebuild requires a different rebuild plan and different machine shop services. Is your vintage Pontiac driven often and you simply feel it’s time to rebuild its engine back to near-stock specs? Are you performing a frame-off restoration and looking to rebuild and restore your Pontiac’s numbersmatching engine? Or are you less concerned with originality and simply looking to increase your Pontiac’s performance while maintaining a relatively stock appearance?

You need to identify the vintage of your Pontiac V-8 and determine if the existing components are capable of meeting your performance expectations in stock or mildly modified form. If your machinist is unfamiliar with the various Pontiac castings and the capacity of each, then it may be best to use one of the many proven combinations found in chapter 9, or contact one of the many Pontiac builders listed in the source guide. The answers you receive should include recommendations for total engine displacement, which pistons, connecting rods, rings and bearings should be used, and the camshaft specifications and cylinder heads that help you reach your performance goal during your rebuild.

There are two other important questions that you must ask yourself when planning your engine rebuild. How much money do I have to spend on the entire project? And how much of the actual engine assembly work am I willing to perform myself? Only you can answer all these questions, and it is common to be undecided at this point of the rebuild. You do, however, have to take a realistic approach and need to stick close to your plan once you commit to it.

When considering all that’s involved in a complete engine rebuild, some hobbyists are more content taking a complete engine to an engine builder and returning when it’s ready for reinstallation; others enjoy performing some or all of the assembly process themselves. Be realistic when assessing your experience and skill level when tackling your engine rebuild because small errors can result in significant consequences and ultimately lead to engine failure. But attention to detail and proper guidance can keep you from making costly mistakes, and that’s the purpose of this book.

Setting Performance Expectations

I know of very few hobbyists who wouldn’t want their Pontiacs to run better. However, most hobbyists don’t gauge “better” by using a drag strip or engine dyno. To most, “better” means the amount of tire spin that occurs upon a brisk takeoff. Depending upon the application and what you’re beginning with, simply performing a basic rebuild to a tired engine may be enough to accomplish that, but some applications might not contain the ideal components to achieve that.

Pontiac designed the components of a given combination to complement one another and perform suitably for its intended application. A particular low-performance engine may have used a 2-barrel carburetor, small-valve heads, and a mild camshaft, but for the most part, its remaining components were the same as those on a similar 4-barrel offering. By simply swapping parts around, generally speaking, it’s quite possible and cost effective to increase the power output of a 2-barrel to match that of a similar 4-barrel offering.

Significantly increasing an engine’s power output almost always requires using high-performance factory pieces, such as those from Ram Air engines, or significantly modifying 4-barrel pieces to extract maximum potential from them. Either of these approaches can be quite costly. Though still expensive, it’s often easier and more cost effective to purchase some aftermarket components designed as replacements for the desirable stock pieces. Additional information on parts selection and power levels are covered in later chapters.

Gathering Required Equipment

If you’ve been wrenching on cars for any amount of time, you likely understand that using the most expensive tools doesn’t make a mechanic great. The absolute best tool for any job is the one that helps complete a given task at a given time, and it doesn’t matter if it was purchased off a name-brand tool truck or from a reputable retailer. Snap-on, Mac Tools, and other brands make professional hand tools for working mechanics. These fine instruments are a pleasure to use and should last a lifetime or longer. However, the at-home mechanic can competently rebuild an engine with Craftsman, Husky, and other highquality consumer tools. But I don’t advocate using low-quality tools that can damage fasteners, round-off bolt heads, and generally make a mess of a basic job.

Before any engine can be rebuilt, it must be completely disassembled, and tearing it down before delivering it to a machine shop can often save you a few bucks. Fortunately for Pontiac hobbyists, V-8 disassembly doesn’t require much beyond basic hand tools for the majority of it. If you don’t presently own such equipment and future plans include additional engine rebuilds or repairs, then you might consider investing in them as they can be handy for most automotive repairs. A list of the tools you’ll need at this time includes:

•Standard 6-point socket set in 3/8- and 1/2-inch drive

•A 1/2-inch breaker bar

•Variety of combination wrenches

•Variety of flathead and Phillips screwdrivers

•Flared wrenches for fuel lines

•Small variety of pry bars

•Soft-faced hammer

•Various taps for thread cleaning

•Digital camera and notebook for documentation

Though generally not regarded as a tool, compressed air is great to have available for a myriad of reasons. An air blow gun can be used to remove decades of dust and grime, especially after being loosened with solvent and a wire brush. Though the use of eye protection is suggested throughout the entire rebuild process, it is mandatory when using compressed air.

Air-operated tools seem to make any job easier. While I often use such equipment for more common repairs, I prefer hand tools when rebuilding an engine. It allows me to feel just how much effort is required to remove or install a fastener, and that can be a telltale sign of thread or fastener damage. A pneumatic impact wrench can be used to remove high-torque harmonic balancer and main cap bolts.

Some specialized equipment, such as a valve spring compressor, engine hoist, and engine stand, are required. But keep in mind: The tools mentioned above are for disassembling and assembling your Pontiac V-8, as well as several other task-specific tools. You might look into renting or borrowing them from friends or parts stores for a single engine rebuild. If additional engine rebuilds are possible down the road, then now might be the best time to add them to your toolbox. However, they are usually more costly and can quickly deplete a budget. The list of those specialty tools includes:

•Engine stand (1,000-pound capacity)

•Engine hoist (cherry-picker type)

•Torque wrenches

•Micrometers and calipers

•Various dial indicators

•Feeler gauges

•Piston ring compressor

One of the most important resources to have on hand during your entire rebuild is a Pontiac service manual that’s specific to the year of your engine. You’re probably wondering why I’d make such a recommendation if you’re reading a book entitled How to Rebuild Pontiac V-8s. Well, there’s a simple answer for that. Though the Pontiac engine family is so closely related, most individual engine models contain at least a few characteristics that are unique to certain model years, and a Pontiac Service Manual should address an area if it varies from what’s shown in this book.

A Pontiac service manual is an excellent resource that can provide information about specific details for a particular model year. Costly reprints are commonly available from various sources, but worn, lower-priced originals are often available on popular internet classifieds or auction sites. A service manual for the model year of the engine being rebuilt is a musthave item for every enthusiast.

A digital camera is another excellent resource that can be used throughout the entire project. It’s beneficial when documenting the position of specific components during assembly. But it also allows you to provide your machinist with detailed pictures of any suspect areas you might have found in the disassembly process. With the relatively low cost of high-resolution point-and-shoot digital cameras and high-volume memory cards, it’s a wise investment for the project and one that can be used for personal use too.

A gasket scraper of some sort is an inexpensive tool that’s used to remove the gasket paper or sealant that’s generally left behind on mating surfaces during disassembly. This unit uses a conventional razor blade that can be changed as often as necessary.

Planning Your Rebuild

The owner of a 1967 GTO had complained that the car’s original 400 suffered from a number of operating issues. It had been rebuilt several years before by a reputable area shop. But the engine simply never lived up to the owner’s expectations in several ways.

The engine was rebuilt with dished pistons to reduce compression ratio, so the original 10.25:1 mill operated suitably on lower-octane fuel, which was ideal for the owner because he planned to frequently take it on long trips to various car shows across the country. After the rebuild, the engine’s coolant temperature sometimes soared; it audibly detonated on occasion and commonly ran-on after shutdown. Though the owner was told the engine could operate on 87- or 89-octane fuel, he found the issues seemed to worsen while using fuel under 91 octane. The engine appeared down on power, it struggled to operate past about 4,000 rpm, and it leaked and consumed oil regularly.

Over the course of several thousand miles operating in this condition, the owner received a number of suggested solutions from fellow hobbyists. Though each was tried with hopes of a miraculous result, none ever really improved the situation, and the owner’s frustration worsened. He approached me and asked for my opinion on the matter, and I agreed to assist.

The first step I took was an initial test drive to better understand the GTO’s operating condition and gather a basis to determine the effects of any adjustments I’d make. Keeping in mind that this particular GTO featured functional air-conditioning, a Turbo 400 automatic transmission, a stock-stall torque converter, and a 2.93:1 rear axle ratio, my initial test drive revealed the owner’s perception of lackluster performance was not exaggerated. This particular 400 ran about as well as a typical low-compression Pontiac 350!

A dial indicator is a useful tool that, when combined with the proper mounting base, can provide useful measurements when rebuilding an engine. This unit was purchased from a local discount tool retailer, and its accuracy is more than adequate for this task.

When torque is applied to a fastener, its overall length increases as it stretches a certain amount, and that stretch can be used to determine its clamping force. Comparing your measurements to the manufacturer’s predetermined values can tell you when a fastener has fatigued, which could otherwise result in failure. A stretch gauge is a valuable tool to measure the length of any bolt after tightening, and it’s most commonly used to measure connecting rod bolts.

A torque wrench accurately measures the amount of torque applied to a fastener during installation and indicates effective clamping load. Adjustable versions like this one give an audible click when the selected amount of torque is reached. A torque wrench is useful most of the time during an engine rebuild but is absolutely required when installing connecting rods, main caps, and cylinder heads. The price sometimes reflects quality and accuracy, so I suggest buying a name brand unit.

A variety of specialized tools are required to fit piston rings to a bore, install rings onto a piston, and insert a piston assembly into a cylinder.

Total Seal offers such products in a wide and affordable array of cylinder sizes.

Plastigauge is an extruded plastic thread designed to uniformly crush, giving a fast and accurate measurement of actual main and rod bearing clearances. It’s best used to verify that your machinist’s measurements were accurate and that clearance actually exists. Simply cut a small piece and lay it on a clean journal, install the bearing and cap, and torque it to the correct value. Compare the spread Plastigauge to the graduated marks on the cover to determine clearance. It should be wiped from the journal surface and bearing coating, but any residue quickly dissolves when in contact with oil.

My attention was first directed toward the carburetor and distributor in an attempt to improve engine efficiency at every point. Though part-throttle drivability had significantly improved, the effect on full-throttle performance was limited, and many of the same issues remained. A compression check proved that cylinder pressure varied throughout the engine. It indicated to us that something was amiss somewhere within the combination and the only way to accurately determine the cause and find a solution was complete engine disassembly followed by a proper rebuild.

Having had several positive experiences with a local machinist, I knew that with his help, we could make this 400 run the way it should. I discussed with him the engine’s existing operating condition, the goals that the owner and I sought, and the time frame we were working within. I explained that, because this was the GTO’s original engine and that it was entered into shows often, original appearance was a key factor. And because of time constraints and for ease of photography, we also needed to have him assemble the Pontiac for us.

A camshaft installation tool attaches to the front snout of a camshaft and provides the assembler with additional control and leverage, ultimately preventing bearing damage during installation. Though available for many other makes, a cam installation tool wasn’t offered for Pontiac applications until Tin Indian Performance began offering this unit, which retails for less than $25.

When dealing with camshafts, a few degrees of valve timing can make a significant difference in the way an engine idles and operates. A quality camshaft degree kit, such as this from Comp Cams (number 4936), allows the assembler to accurately install a camshaft at the desired position in relation to the crankshaft angle. A complete kit like this costs a well-spent $200 dollars.

This lifter bore fixture from Comp Cams (number 4925) is designed to be used in conjunction with its camshaft degree kit. When inserted into the lifter bore, the small extensions, which are intended to replicate a roller and flat-tappet lifter face, ride on the camshaft lobe for maximum accuracy.

The experience leading to the decision to rebuild your Pontiac V-8 may be similar to the example above, or it could be completely different. Nothing changes the fact that this 400 was running so poorly it was basically asking for a rebuild. Your Pontiac may not be quite as bad, but a tired engine needs attention too. Once you arrive at that point, you need to sort out your expectations and goals, set a realistic budget that allows you to achieve them, and prepare to get your hands dirty! ■

Valvetrain geometry can be affected anytime a block is surfaced or a cylinder head is machined. The easiest way to restore proper alignment of the valve stem and rocker arm is to utilize a specific-length pushrod. Comp Cams offers adjustable pushrods like this, which can be used to determine the required length of the replacements.

A dyno simulator computer program can never take the place of an actual engine dyno, but it can be a useful tool when determining the effects certain components can have on an engine’s performance. Performance Trends Engine Analyzer v3.4 is among the best programs available. It allows hobbyists to compare how different camshafts, intake manifolds, cylinder heads, and exhaust systems can affect engine operation, and it contains excellent displacement and compression calculators. I have used one for years and have found it to be an excellent learning tool.

Selecting a Machine Shop

Once you’ve laid out the rebuild path you plan to follow and have the proper equipment on hand, the next step is to locate a reputable machine shop in your area that can satisfy all of your needs. The best choice is one that comes recommended by fellow Pontiac hobbyists who have had direct experience with a shop. You may find some shops with several caveats and others with several attributes.

A magnetic pick-up tool is handy if you’ve dropped something like a nut or washer into a crevice or the tight confines of the crankcase. A telescoping tool like this or one with a flexible head is an inexpensive purchase at your nearest parts store.

In my opinion, a reputable, professional shop should be clean and able to perform such tasks as sonic testing, magnetic-particle inspection of components for cracks, fully machine a block and crankshaft, rebuild cylinder heads, prepare connecting rods, and completely balance a rotating assembly. It should also be able to procure replacement components, such as pumps, gaskets, and seals. Specialized procedures, such as nitride or cryogenic treatments, are often beyond the resources of typical engine building shops.

A complete tap and die set can be a valuable asset when cutting new threads into metal or restoring the shape of an existing one, but they’re generally rather pricy. Only a handful of basic taps of various sizes and thread pitches are needed during an engine rebuild to chase the threads found on any cylinder head or block.

If a machine shop must send any component to an outside company for specific machining processes, then the machinist should assume full responsibility for any failure that occurs and is found to be related to the component that was outsourced. Just the same, you can’t expect a machinist to stand behind any complete component you bring to the rebuild from an outside vendor. A machine shop technician must be able to work with a complete selection of compatible and complementary components because all the components must work in harmony to complete a strong, reliable engine. In addition, the machinist must be able to fully inspect each component and verify its parts, function, dimensions, and overall quality. If the machinist is not able to do this, the slightest problem or mistake can lead to a catastrophic failure. An example of this might be valvetrain failure related to cylinder heads that were improperly prepared by an outside vendor.

A valve spring compressor is required to completely disassemble and reassemble cylinder heads. Though units of various arrangements are available, I prefer a C-clamp style like this. It’s better to spend a few more bucks for a high-quality unit like this one from Snap-on that won’t flex under pressure.

This valve spring micrometer and other similar units determine the installation height of a valve spring when combined with the particular length of valve and retainer that’s being used. Available within specific ranges, this Comp Cams unit measures from 1.4 to 1.8 inches.

Most machine shops can assemble certain components you’re unable to handle yourself for whatever reason. For instance, cylinder head assembly includes measuring valve spring pressure and installing valve springs at the proper height. Allowing your machinist to assemble them is often a wise move. If you’re concerned with the critical measurements and minute clearances associated with the rotating assembly, or if correct rod and piston orientation is intimidating, your machinist may be able to assemble the short-block for you at a reasonable cost or suggest a certain engine assembler for you.

Various telescoping gauges, calipers, and micrometers are essential tools when performing any engine rebuild. They can be used to verify the measurements of most components. Units like these can be purchased at a reasonable cost from a local discount tool retailer. They’re accurate for engine-build measurements.

A dial-bore gauge can be used to measure areas of the block, such as the bore diameter, cylinder wall taper, and diameter of the camshaft tunnel and main caps. This unit was purchased from Summit Racing Equipment, cost less than $100, and has been very useful.

No matter how much or how little of the engine rebuild you intend to perform yourself, you need to find a machine shop that can meet your machining requirements. You want to find a shop that has rebuilt and/or machined many Pontiac V-8 engines because you don’t want a shop to make mistakes. If they have to learn the specs and machining processes while working on your engine, the chances of making mistakes are much greater. If you don’t have one already in mind, finding the best choice for you can be as easy as asking around to gather opinions. This may be as simple as attending local car shows and asking fellow Pontiac owners who they’d recommend for an engine rebuild.

After striking up a conversation with a Pontiac owner, clearly ask if the Pontiac’s engine has ever been rebuilt and if so, by which owner. Remember, you’re looking for first-hand experience with a machine shop. Here are some general questions to ask:

•Why did you select this machine shop?

•What was considered a complete engine rebuild?

•Was any portion of it sent out to another shop?

•How long did it take to complete your project?

•How long were you told it would take?

•How much work did you perform yourself?

•Were you completely satisfied with the results?

•Did the cost seem reasonable for what you received?

•Have you had any issues with your engine since the rebuild?

•Would you use this machine shop again?

If you’re satisfied with the answers to these questions, simply consider that machine shop as a possibility and move on to the next Pontiac owner for another opinion. Remember, when dealing with the minute tolerances associated with an engine rebuild, one can go wrong from time to time. A quality machine shop stands behind its work, however. Once you’re completely confident in one shop’s ability, you’re ready to contact them to inquire about the services offered.

A feeler gauge is used to measure the clearance between two perpendicular mating surfaces. And when combined with any precision straight edge, it can be used to measure cylinder head or deck surface warping. Units like this are available at any parts store and generally cost less than $20.

The term “machine shop” is often interpreted as a business that can rebuild an engine for a customer, but there’s a major difference between the services offered by an actual machine shop and engine assembling and building shops.

While modern machine shops often offer both machining and assembling services, some machine shops have no interest in assembling an engine after the machining portion a rebuild is complete. In these instances, it is your responsibility to completely assemble your engine or enlist the services of an engine assembler.

With so many affordable aftermarket crankshafts for other makes available today, there aren’t many modern machine shops that grind crankshafts in-house anymore. If your rebuild requires this, and if the machine shop you select subcontracts the task, ask for the name of the company.

A high-quality machine shop should possess the equipment required to properly machine a Pontiac block. That includes using a Pontiac-specific torque-plate for boring and honing cylinder walls and a line hone to restore main journal geometry.

Balancing the reciprocating assembly involves attaching stationary weights to crankshaft journals, which replicates the effects of the piston-and-rod assemblies. The crankshaft is spun at low RPM and a strobe light is used to determine where counterweight mass should be added or removed to ensure smooth operation.

An engine assembling shop in simplest terms is just that: a shop or a person that assembles engines for customers. Some or all of the component machining is outsourced and the entire combination is assembled with little regard toward maximizing performance. The engine is typically fully assembled and ready for installation into a vehicle, but it may or may not have been fired prior to customer delivery and usually does not include any form of tuning.

An engine builder is best described as a person or a shop that designs and assembles a customer’s combination. It includes performing or arranging machining by one or more competent machine shops and selecting the proper combination of components to help a customer achieve his or her performance expectations. Engines are typically delivered to the customer completely assembled and fully tuned, and the output should be documented with the results of dyno testing.

There are distinct markets for all three services, and that’s something to consider if you’re going to have a shop assemble any part of your engine for you. No matter which route is chosen, have a clear understanding of how your components are being machined and which machine shop is handling the task. It may be worthwhile to visit that machine shop before making a decision on moving forward.

In my opinion, a good machine shop is one that can completely rebuild any engine in a timely manner with its own in-house equipment. I feel that outsourcing any part of a rebuild can compromise a project. The machinist tends to lose control of time and quality, and that can negatively affect the outcome. A quality machine shop to consider for your project should possess the following equipment:

•Parts cleaning equipment

•Cylinder honing equipment and a Pontiac-specific torque plate

•Line-hone equipment

•Vertical mill

•Surfacing equipment for heads and block

•Rod preparation equipment

•Crank grinding and polish equipment

•Balancing equipment

•Valve refacing equipment

•Valve guide and seat equipment

The high numbers of low-cost aftermarket crankshafts currently on the market has limited the number of cranks that a machine shop must prepare on a regular basis, and the high cost of such equipment can prevent newer shops from purchasing a crankshaft grinder. Unless your plans include an aftermarket Pontiac crankshaft, however, the machine shop you choose should have that ability to perform that task or confidence in the company it outsources it to.

Any quality machine shop should have modern valve guide and seat equipment to precisely prepare its customer’s cylinder heads. This equipment from Serdi can cut multiple angles into a valve seat in a single pass, using the valve guide to properly locate the cutter in relation to the seat.

I also feel that the best shops are those that offer engine break-in with a test stand or engine dyno. This allows you to verify that your engine starts immediately, idles and revs smoothly, is free of oil and coolant leaks, and ultimately confirms that your engine has been broken-in properly before ever leaving the machine shop. If you chose to spend the extra money, a dyno tune can be a great tool to measure your Pontiac’s output and ensure that it’s performing reliably and optimally under full-throttle conditions.

Before contracting a shop for your rebuild, clearly discuss your expectations and specifically disclose the wear parts (valve springs, bearings, gaskets, etc.) you’ll be expected to buy from them. Most businesses have some type of policy in place that allows it to add a certain percentage onto the cost of the project if a customer supplies parts, and at that point, any warranty against failure is void. Some shops may even go so far as to simply refuse to assemble anything they didn’t supply. Some shops just aren’t willing to take this risk of failure.

If new valves are part of your rebuild, then there’s a chance that your machine shop does not need to use this piece of equipment. If you’re planning to reuse your existing valves, however, a valve grinder like this is required to restore the surface of the seat angle or add other cuts that could possibly improve airflow.

A surface mill is required when removing material from the mating surfaces of a block or cylinder head. Other uses include resurfacing a manual-transmission flywheel, or intake or exhaust manifold flanges. It’s a valuable piece of equipment that any machine shop should have.

Once you have selected the machine shop you feel most comfortable working with and your rebuild project begins, it’s advisable to check in often to follow your engine’s progress. Asking questions and being visible is an easy way to learn and to be sure your project is on track. But you must also understand that, in business, there’s a fine line between being inquisitive and being a pest!

When Rebuilds Go Bad

A good machinist takes pride in the work and sincerely feels that what leaves the shop is as functionally sound as if it were as good as or better than new. Just because a machinist has good intentions doesn’t mean that accidents can’t happen, however. A good machinist can have a bad day, but the best machinists routinely check their work throughout the course of any task to prevent any associated failure.

For any number of reasons, it’s sometimes easier to allow a shop to assemble your engine for you, and careless assembly can have a catastrophic outcome. If you choose to handle your own assembly, as a smart owner you can check your engine’s tolerances just before assembly to be sure your machinist wasn’t having a bad day when machining your components. That might help you gain trust in the machinist and the shop if future engine rebuilds or various projects are on the horizon.

It’s obvious that a significant amount of material has embedded into this bearing. As bad as this might look, it actually performed its intended task. There was almost no major wear on the corresponding crankshaft journal.

By design, bearings are sacrificial components. Minute particles passing through the lubrication system embed into them, saving the crankshaft journals. Once a bearing is no longer able to perform that task, distinct wear patterns can begin appearing on the corresponding crankshaft journal surface. This crankshaft was reused after removing 0.020 inch of its surface.

This connecting rod bearing has experienced complete failure. Metallic particles in the lubrication system and extreme heat wore through all of the Babbitt layer and most of the copper layer, exposing the metal backing.

A local assembler rebuilt this Pontiac 455 for its owner. It was a very basic rebuild like many of the Pontiacs the assembler rebuilt before. But it wasn’t broken-in on a test stand before it was returned to the owner. The owner simply installed it into his Pontiac, and it immediately started showing signs of significant internal issues. After a handful of miles, it was evident the freshly rebuilt engine required an immediate teardown. These photos reveal what was found.

Working with an independent machinist to gain an understanding of what occurred, the best guess seemed to be that the rear camshaft plug was driven in a bit too far, and when the camshaft thrust plate was installed, all camshaft clearance was lost. It appears unlikely that the engine assembler had checked for any clearance during the rebuild.

With the camshaft’s first revolution after immediate start-up, it’s evident that it churned into the steel plug, which sent metallic filings into the oiling system, where material was distributed throughout the entire engine. The metallic particles quickly damaged the piston skirts and bearings, several of which failed completely.

This steel plug was driven too far into the rear opening of the camshaft bore, and when the camshaft and thrust plate were installed, the engine assembler neglected to check for proper clearance. The wear that followed sent metallic particles throughout the engine, causing a significant amount of damage and effectively destroying a freshly rebuilt engine.

After removing the bottom plate from the oil pump body, there’s no question that metallic particles were being carried throughout the engine by its oiling system.

Unfortunately, another set of new pistons is required during the rebuild. The deep grooves and embedded material can prevent the piston from properly maintaining cylinder seal.

Unfortunately, examples like this are common. Though it may have looked like this 455 would never run again, it was completely disassembled and the reusable components were thoroughly cleaned. Several new components were purchased and the entire engine was properly rebuilt by another machinist shortly after these photos were taken. It has since given its owner a number of issue-free miles, but it was a rebuild that cost this owner twice as much as it should have. ■

Found while rebuilding a different engine, the dark areas on the deck surface of this block are soot trails. This indicates that the cylinder head bolts used on this engine were not torqued properly or fatigued from overuse, or that the head gasket didn’t crush properly during cylinder head installation. Regardless of the cause, it eventually resulted in head gasket failure.