Читать книгу LS Swaps - Jefferson Bryant - Страница 8
ОглавлениеThe first piece of the puzzle of any engine swap is to actually mount the engine into the chassis. This can be as simple as bolting a set of adapter plates to the block or as complicated as fabricating an entirely new pair of frame stands. It all depends on the chassis. This chapter covers the gamut, from simple to complex fabrication of motor mounts and transmission mounts to making the connection from the transmission to the rear differential.
The key to any swap is installing the engine in the chassis. This can be easy or it can take weeks to figure out: it all depends on the car. General Motors certainly helped swappers by using the same motor mount design for all Gen III/IV engines, with the exception of the LS4, which is a front-wheel-drive platform.
Vorshlag Motorsports makes many LS swap kits for BMWs. This one is designed to swap Gen III/IV engines into E36 BMWs (E-series). The kit is available in many stages from bare-bones engine and transmission mounts to everything you need, including headers and driveshaft. (Photo Courtesy Vorshlag Motorsports)
The LS engine uses a four-bolt mount that installs on the side of the engine block. The typical solution for this change is simply converting the LS engine to the more common early-style three-bolt motor mounts. The original 1955 small-block featured the three-bolt mount configuration, and the same pattern continued in production through the second-generation small-block: the LT1 and LT4 engines.
Basic adapter plates are the most common solution for LS engine swaps. They bolt to the Gen III/IV four-bolt motor mount pad and allow a three-bolt GM motor mount to bolt on, and they work with most headers. Made of rugged 3/8-inch-thick hot-rolled steel, they are zinc plated and include countersunk machine screws.
Installing adapters to an engine block is rather simple. Torque the four socket head bolts into the block using an Allen key socket. Most motor mount brackets are torqued to 37 to 43 ft-lbs, but follow the specific recommendations from the motor mount manufacturer. In addition, use some anti-seize compound to prevent galling of the different metals.
The GM three-bolt motor mount bolts to the upper studs, and the lower mount uses the stock LS bolt hole. There are different designs, and some adapters shift position on the engine front or rear depending on the application. These Speed Hound Performance mounts are designed for the C2/C3 Corvette. Using a stock small-block Chevy motor mount, they bolt directly to the factory frame stands.
LS-series engines are similar dimensionally to the classic small-block Chevy engine, so they fit anywhere a small-block Chevy does. The conversion from a small-block Chevy to an LS can be as simple as using adapter plates.
Many companies make adapter plates to convert the LS mount to accept a small-block Chevy three-bolt mount. With so many adapters available (there are literally hundreds of different brands), deciding which one to use is the tough part. The stock LS engine motor mounts are located farther back toward the bellhousing than on the Gen I/II blocks. If a motor mount is bolted to the frame using these holes, in most vehicles, the engine sits too far forward. This increases the nose weight of the car, causing instability. Some adapter mounts are for specific applications, such as the GM first-generation F-Body or A-Body cars. Some manufacturers, such as Holley, offer different adapters with offset mount locations such as “1.25 forward” and “.5 up” to better facilitate engine placement for chassis and body clearance. Other manufacturers have adjustable adapter plates, so you can get the positioning just right for your application.
Depending on the style of mount, the motor mount cup may have a hump that must be removed to attain the correct amount of clearance. A disc sander or grinder quickly removes it.
Once the center hump has been removed, the small-block Chevy mount should bolt up to the adapter. The clamshell-type mounts typically need to be ground down to the proper clearance.
These mounts from Autokraft feature a recessed area milled into the adapter plate, allowing the hump on some small-block Chevy motor mounts to fit without any additional work.
All adapters are not the same. This kit from ATS flips the small-block Chevy mounts upside down to position the engine lower in the chassis. These are designed to fit the first-generation Camaro and the GM A-Body, but they are compatible with other chassis and LS engine combinations. (Photo Courtesy ATS Performance)
By simply bolting the adapter plate to the engine block, you have mounting provisions for the old-style three-bolt motor mount. For GM vehicles or cars that have already been converted to a small-block Chevy, this allows the LS-series engine to drop right into the chassis with no re-engineering.
Swap Kits
American Touring Specialties (ATS) offers a set of LS adapter plates that feature an early-style motor mount in an upside-down configuration. ATS offers this arrangement so the engine is able to sit lower in the car and farther back from the firewall, allowing for better stability and a lower center of gravity. With these ATS mounts, an LS engine can be swapped into most any GM muscle car.
That is not to say that every GM car fits the same way. Vehicles such as the 1994–1996 Impala SS originally had an LT1. The stock LT1 motor mounts on these vehicles are set a little farther back than the Gen I small-block. To compensate for engine position, the Impala mount from Street & Performance (for example) moves the motor mounts on the LS adapter plates back 1 inch, so the engine is correctly positioned in the frame while maintaining proper weight distribution. The Corvette has always been the flagship model for Chevrolet and General Motors. When the Corvette received the first LS1 in 1997, owners of older Corvettes wanted one also. Unlike other GM vehicles, however, Corvettes have a few additional impediments for an LS swap. Although you can make a standard LS adapter plate work, you have to modify engine components, which is expensive and time consuming. Speed Hound Performance has the solution: a specialized motor mount designed specifically for the 1968–1982 and 1984–1996 Corvettes; they also work great in the C2 (1963–1967) chassis.
Some adapters require a lock nut on the back side of the plate, such as these Trans-Dapt mounts. The external webbing makes these adapters a bit more difficult to install. The locking nuts are recommended to add extra security.
Once the locking nuts have been installed on the back side of the plate, the bolt is tightened in the threaded plate and then the lock nut is tightened.
Street & Performance offers many different adapter plates to correctly position the engine in different chassis designs. These plates fit the Tri-Five GM cars. This is called a biscuit mount, and many early GM V-8 chassis use this style of mount. (Photo Courtesy Street & Performance)
Another staple for LS engine swaps is the classic Tri-Five Chevy, otherwise known as the 1955–1957 Chevrolet. Other GM offerings from the Tri-Five era include Buick, Pontiac, and Oldsmobile. These cars used a different-style motor mount called a “biscuit” mount. These early-style mounts bolt to upright pads near the front of the engine on the frame. A steel bracket then reaches from the motor mount pads to the uprights. A rubber disc, referred to as the “biscuit,” rests between the pads and the uprights to absorb the twists and shock from the running engine. These mounts easily bolt to the adapter plates to make an LS swap simpler and more convenient.
Many LS engines do not clear the brake booster and other accessories in certain chassis; therefore, you need to find a smaller, compact brake booster to install. This is a stock full-size 9-inch booster. (Photo Courtesy Street & Performance)
You may need a smaller brake booster to overcome the fit challenge. Make sure it provides enough braking power for your particular application. A smaller booster often mean less braking power. This is a 7-inch booster. (Photo Courtesy Street & Performance)
This hydroboost from Power Brake Service is an alternative to the vacuum power booster. It not only provides the needed clearance, it also delivers exceptional braking power. The braking force with a hydroboost is impressive; even stock brakes see a serious increase in performance. The hydroboost gets its power from the power steering pump, which is more reliable than simple vacuum.
Non-GM Swap Kits
It isn’t just muscle cars and GM vehicles that are candidates for LS swaps. LS-series engines have been installed into BMWs, Volvos, Hondas, even Fox-Body Ford Mustangs and Mazda Rx-7s. Non-traditional LS swaps require more effort, so it pays to do your homework and research what others have done.
It is imperative to check for proper fitment of all aspects of the swap: engine/transmission, brake control, steering, and cooling all must be considered. You must verify that the engine bay can hold the engine; if not, you have to modify it. If any of the chassis components (brakes, steering, etc.) have to be relocated, that adds complexity to the swap.
The transmission and drivetrain must be compatible as well. Installing an LS3 into an S10 chassis is fairly easy, but the stock 7.5-inch rear end is not going to last very long with that kind of power. These are some of the considerations you need to keep in mind when looking at an LS swap for a non-GM vehicle.
Most LS engine adapters position the engine closer to the radiator. Many owners opt to use an electric fan so this clearance is not needed. (Photo Courtesy Street & Performance)
Hooker’s LS swap kit for the Nissan 240SX features a transmission crossmember bracket and motor mounts. These allow the installation of an LS engine into an S13 Nissan body along with a T56 manual transmission. This kit is compatible with the Canton Racing oil pan, expressly designed to fit in the S14 Nissan chassis. (Photo Courtesy Holley Performance Products)
LS swaps have become so popular that companies are building kits for many of these vehicles. Vorshlag Motorsports manufactures an LS swap kit for 1991–1999 BMW E36 (3-series) models, complete with all the components required for installation. This complete kit contains motor mounts, transmission crossmember, headers, steering shaft, driveshaft, and all the necessary hardware. It also includes optional components: a hydraulic throw-out bearing kit for manual transmissions, radiator, coolant lines, power steering, and fuel pump.
Some vehicles readily accept the LS engine because the chassis, frame rails, and mount system are similar to the stock setup. Other vehicles are dissimilar and require custom fabrication. This twin-turbo LS-powered Volvo wagon needs a completely new front crossmember. (Photo Courtesy Doug Strickler)
Another excellent resource for non-GM swap kits and components is Hinson Supercars. Hinson has the components for most imports such as the Mazda Rx7s and Rx8, Honda S2000, and Nissan Z-cars.
Mounting an LS engine between the frame rails is only one part of the job; you also need to support the rear of the transmission. With the exception of an extra bolt at the top, the bellhousing pattern on the LS engines is the same as on the small-block Chevy. This allows just about any traditional Chevy bolt-pattern bellhousing to bolt to an LS engine. Adapting the transmission mount to each vehicle usually requires a combination of stock components modified with new mounts.
ATS offers this adjustable transmission crossmember for the first-generation Camaro/Firebird. It allows the location of the transmission mount to shift, accommodating different transmissions and different engine setback/forward specs. (Photo Courtesy ATS Performance)
If you have a GM A-Body, you may be able to reposition the factory crossmember to another set of holes. Remember, an early transmission sits about 2 inches back from the LS engine. This is due to the lack of extra material on the back of the LS block.
When building a custom transmission mount, be sure to center the transmission in the frame. Measure the transmission centerline. Follow the input shaft to the output shaft along the length of the case and start from there. On this 1963 Buick Wagon (which has an X-frame), the transmission mount started with a piece of angle steel bolted to the factory locations, extending about 6 inches past them.
Interchangeability
For most GM chassis, there are simple adapters available to fit most GM transmissions, particularly with 1964-later cars. Before 1964, each GM division was separate; they shared a few core items, including the frame, and sometimes basic component design, but the details changed.
For example, a 1960 Chevy B-Body (Impala, Biscayne) used the same frame as the Buick B-Body (Le Sabre, Wildcat), but none of the parts interchange, not even the rear end. They look similar, but the parts don’t fit. This is important for swappers to know. In the case of transmission mounts, a Buick Dynaflow is completely different from a Chevy Powerglide.
In 1964, General Motors started using “corporate” parts, so a control arm for a 1964 Pontiac LeMans fits a 1964 Chevy Chevelle or Oldsmobile F85. The bigger cars started using corporate parts a few years later, as the body styles expired and new styles were rolled out.
For most GM muscle cars, the stock crossmember can be modified to fit late-model transmissions, such as the T56 manual transmission and the 4L60E automatic. With the engine mounted to the frame, the transmission must be supported in front of its mount for access during the fabrication process. For example, you can use a block of wood to keep the transmission oil pan from buckling under the weight.
Clearance
Firewall clearance must also be considered when using an older GM transmission with an LS engine. The Gen I small-block was designed with offset cylinder heads. As a result, there are about 2 inches of space between the bellhousing mounting pad and the back of the cylinder heads.
Use an angle finder to set the transmission at the proper 3-degree downward angle for proper driveline adjustment. The rear end should have a matching upward angle. The U-joints must be “working” to last. If the joints are positioned at 0 degrees, there is no load on the bearings, which allows them to move around, generating excess heat and causing premature wear. Therefore they wear out much faster.
Keep this in mind when deciding whether to use the stock transmission in a GM muscle car or truck: the Gen III/IV engines do not have offset cylinder heads, and therefore do not have any space between the bellhousing and the cylinder heads. The cylinder heads are flush with the back of the block. The heads are not necessarily longer, but the back of the block is actually a little shorter.
Most adapter plates provide a space of about 2 inches between the back of the engine and the stock transmission in the stock location. As a result, it’s often necessary to relocate the transmission mount and/or move the transmission crossmember to bring the two components together.
Custom Mount Fabrication
Custom frame stands can easily be made using a few pieces of scrap steel, but you need to have some welding and fabricating experience to make them.
This mount was fabricated for a Buick wagon. Use an angle grinder to cut two pieces of angle iron and then place them into the motor mount. Then cut a piece of tubing to fit between the channels.
Chamfer the tubing so it fits tight to the bottom of the angle in the channel. The angle steel has a rounded inner edge; chamfering the edges allows the tube to sit flush on both flat surfaces, yielding a better fit.
With the fit set, mark the bolt location on the new metal and drill out to the correct 1/2-inch bolt size. Drilling it before it is welded allows for the hole placement to be adjusted, so the two holes line up with each other.
Using the drill bit to maintain the channel’s location, weld up the mount, including the tubing. Even though the metal is 1/8 inch thick, it is important to weld the joints in short sections to avoid warpage.
Position the completed frame mount in the car and weld it to the frame. Before welding the mount to the frame, it is a good idea to paint the back side with a high-zinc weld-through coating to protect the metal from rust.
Cut another piece of angle steel to size and position it between the side mounts. Using the transmission as a guide, note the position for the transmission mount. The steel is 10 gauge (1/8 inch thick).
Place the cross beam on the side beams. If it sits a little high, mark and notch the side beams so you tack weld the cross beam in the correct position.
Remove the entire assembly from the chassis and fully weld it. Make sure that you get good penetration of the metal for the welds. Place beads of weld in lengths of 1 inch or less to avoid warpage.
The transmission mount hole usually requires a little play, so they typically have a short slot for adjustment. Note that the ends are boxed in to the main tube, which adds support to the mount plate.
When using box tubing for any type of mount, it is always a good idea to make a support tube inside. This keeps the tubing from crushing under the stress of the bolt and the weight of the transmission.
The 4L80E in this 1962 Comet wagon required a 3-degree down angle, and that meant it needed a dropped crossmember. This was made with five sections of 1×2 tubing cut to the proper angles and welded together. Each section was fully boxed.
This diagram shows the formula for balancing. The red dot in the center is the actual rotational center; the yellow dot shows the center of mass. This represents an unbalanced shaft. The distance between the rotational center and the center mass determines how much weight needs to be added to shift the center mass to the rotational mass.
This cast-steel Dana slip yoke is a high-strength unit that withstands up to 800 hp, depending on the application. Although a stock-type slip yoke can transmit up to 500 hp, a 40-year-old yoke may have many micro-cracks and weak spots that can become a failure point at far lower power levels. You can Magnaflux the U-joint, or you may determine that the U-joint has reached the end of its service life and needs to be replaced. (Photo Courtesy Dana Spicer)
When approaching the 800-hp mark, look into billet slip yokes. Machined from a single block of billet steel, these yokes can handle just about any power level.(Photo Courtesy Dynotech Engineering)
Driveline Angle and Crossmember Modification
When installing an LS engine, getting the driveline angle correct is critical in terms of strength and reliability. The transmission must be angled between 1 and 5 degrees downward on the yoke. For performance applications, 2 degrees is optimal. An angle finder (available at most hardware stores) can determine this angle. Place it against the tailshaft and let the needle rest until it points to the drive angle. If the stock crossmember bolts to the engine and the drive angle is between 1 and 5 degrees, it works.
If the drive angle is not between 1 and 5 degrees, the crossmember must be modified. There are several methods to attack this problem; it all depends on the crossmember. If the crossmember is removable, it can be lowered with spacers, or the transmission itself raised with spacers placed under the mount. Sometimes the crossmember must be modified by cutting and welding new tabs or mounts.
For example, the C2 Chevy Corvette does not have a removable crossmember, and the mount is not adjustable. The mount must be cut out and a recessed mount welded into the crossmember.
With many non-GM vehicles, the stock transmission crossmember can be retained and modified. If that’s not possible, a new crossmember is required. The key here is the driveline angles and keeping the tailshaft square between the frame rails.
Once welded, the driveshaft must be balanced. This Balance Engineering balancer spins the shaft to 5,000 rpm, ensuring a proper balance for high-performance applications. This machine has the capability of revving to 7,500 rpm.
The driveshaft is a critical component of the vehicle, and you cannot risk a driveline failure because you may lose control of the car. When shortening and re-welding a driveshaft, you should rely on a professional shop to perform the work. Choosing a qualified driveline shop is important. Dynotech Engineering uses CNC-operated welders to ensure a perfect weld every time.
When fabricating crossmembers to support the transmission, it is important to note that the materials used must be strong enough to hold the weight and torque of the transmission. Tubing (round or square) is a good material to use, as the tubing provides structural stability with less overall material thickness and weight. Using flat plate steel requires thicker material to achieve the same structural integrity. Angle steel is another excellent material for custom transmission crossmembers.
When performing an engine swap, the driveshaft often needs to be replaced. Simply shortening the stock driveshaft is not really the best solution. With all of the engineering, time, and effort you are putting into an LS engine swap, why use the same old driveshaft that will never work like a properly designed custom unit?
The final piece of the driveline puzzle is the pinion yoke. The chances of breaking one are small. The compact design means more meat in the important places, yielding a strong component. A cast yoke is not bulletproof, but a billet steel yoke, such as this one from Mark Williams, is pretty close. New yokes also usually come with better joint caps rather than lighter-weight stock-style U-bolts, which are prone to distorting the U-joint bearing caps. (Photo Courtesy Dynotech Engineering)
A design is only as good as the workmanship that goes into it. Building the right driveshaft for the application is critical; every high-performance vehicle should have a driveshaft professionally built by a shop that specializes in high-performance drivelines. Or, you can order a driveshaft from a reputable high-performance builder.
Either way, be sure to specify it is for a high-performance application, which is very different from a stock driveshaft, and needs to be held to a higher standard.
In the end, the driveline is perfect for a swap.
Driveshaft Balance
In most cases, installing an LS engine in a vehicle increases the torque and horsepower output. Anytime power output to the stock driveline is increased, the impact of that increase on the stock driveshaft must be taken into account. Most factory driveshafts are balanced between 3,000 and 3,500 rpm, which means spinning the driveshaft faster than 3,500 rpm can have a parasitic effect. In fact, Steve Raymond, from Dynotech Engineering said, “We have had several NASCAR teams tell us that our driveshaft saves them 3 to 7 hp on their chassis dynamometers. That’s why balance is important and why we manufacture shafts for about 85 to 90 percent of the NASCAR teams.” The stock balance on the stock driveshaft is not good enough for anything but a stock engine.
Dynotech uses Balance Engineering’s driveshaft balancers, which are considered to be the best for accuracy. Dynotech recommends balancing a performance driveshaft at a minimum of 5,000 rpm, and as high as 7,500 rpm. This ensures a properly tuned driveshaft that reduces parasitic loss of horsepower through harmonics and vibration.
Here is a fully welded aluminum shaft and yoke. Note the clean CNC-welded joint. You cannot achieve this level of welding at home, so it’s best to leave this work to a professional shop. (Photo Courtesy Dynotech Engineering)
Both slip and pinion yokes are critical driveline components. They physically connect the transmission, driveshaft, and differential. Break one of these and you have a disaster on your hands. That being said, a cast yoke is usually good enough to handle up to 800 hp in most applications. That number has some fudge room, though, as a lightweight hot rod with street tires and 800 hp puts less strain on the driveline than a 4,000-pound Chevelle with slicks and 500 hp.
Another option when using a cast pinion yoke is to use U-joint caps instead of the weaker stock-style U-bolt retainers. This increases the holding power and eliminates the possibility of distorting the caps. New billet yokes typically come with the proper retaining caps.
A driveshaft that is too small in diameter for its length is often inefficient. It can bend and produce parasitic drag on the drivetrain, eating up horsepower. The first type of bend is referred to as first-order bending. Once this starts, the shaft begins to flex up and down, and it “jump ropes.” When driving the car, you feel a significant vibration that will eventually fatigue the shaft and U-joints. (Photo Courtesy Dynotech Engineering)
Reaching critical speed causes first-order bending. This complex formula is used to calculate the critical speed for every driveshaft. All driveshafts have a critical speed, depending on their length and diameter. The shaft material elasticity is an important part of the equation. This is the material’s ability to resist non-permanent elastic deformation. For a driveshaft, this translates into bending. The higher the modulus of elasticity (MOE), the less it bends.
Getting these numbers can be a little tricky because most shops keep the specific numbers they use as trade secrets. For steel, the basic MOE is 30, aluminum is 10, and carbon fiber depends on the manufacturing processes used, so no general numbers are available.
Driveshaft Length and Diameter
Other than balance, the length and diameter of the driveshaft directly affect the performance of the unit. Determining the required length for a driveshaft necessitates looking at several factors. The distance from the rear yoke to the transmission seal is the most important measurement. In turn, it is important to measure this length with the pinion yoke installed and set (and the car sitting at ride height). Changing to a billet pinion yoke can alter the length by as much as 3/4 inch.
With this measurement, the driveshaft shop can create the complete shaft with the required slip yoke and pre-determined run-out for the slip yoke. For most applications, slip yoke run-out (the length of yoke shaft that extends out of the transmission) of 1 inch is more than enough to provide the play needed for suspension travel.
Do not let a shop talk you into leaving more run-out than that. Some transmission shops insist on running out 1.5 inches, which could be disastrous. With that much of the slip yoke hanging out of the transmission, there could be fewer than 3 inches of splined yoke in the transmission, thus creating a wobble in the yoke, which causes a heavy vibration at various RPM. Stick with the 1-inch rule and always measure the driveshaft length at drive height.
The type of U-joint is more important than most people think. A “lubed for life” Spicer U-joint (left) is stronger than its same-size greaseable counterpart (right). (Photo Courtesy Dynotech Engineering)
Here are three common sizes of U-joints, from the left: 1350, 1330, and 1310. The 1310 is the most common U-joint, found in most cars. Performance yokes are made of the 1350 series U-joint, although larger and smaller units can be found. Make sure to use the same-series joint throughout the entire driveline. A drivetrain is only as strong as its weakest link. (Photo Courtesy Dynotech Engineering)
If the vehicle is too low to get under it on the ground, jack up both ends and use jack stands under the rear end and front suspension, and be careful to make sure all the stands are at the same height. The slightest variation can throw off the measurement, resulting in a driveshaft that does not fit.
Driveshaft Critical Speed
Critical speed (CS) is the RPM at which the driveshaft becomes unstable and begins to bend in the middle. This is also known as “jump roping” (because it actually looks like a jumping rope). The longer and smaller (diameter) a driveshaft is, the slower its critical speed. CS is felt as excessive vibration, and if run at CS too long, the unit fails.
To calculate critical speed, the length, diameter, wall thickness, and the material module of elasticity must first be identified. Then, using the critical speed calculation formula on page 21, you can plug in your numbers to determine the driveshaft’s critical speed.
For trucks and exceptionally long vehicles, consider using a carrier bearing. It essentially cuts the driveshaft into two pieces. One half is in a fixed position (it neither moves up/down nor does it slide in/out with suspension movement) to the transmission, and only the carrier unit rotates. The other half uses a slip yoke to the carrier unit and mounts to the differential.
Although most full-size trucks use carrier bearings to minimize vibrations and reduce the overall diameter of the driveshaft, they are definitely not as strong as a one-piece unit. Given that a two-piece shaft has twice as many connections and U-joints, the opportunities for failure are twice as high.
Driveshaft Material
The composition of the driveshaft is just as important as the length and diameter.
Steel: OEM steel driveshafts are for just that, OEM power. An OEM shaft is rated for no more than 350 ft-lbs, or 350 to 400 hp. For high-performance use, drawn over mandrel (DOM) seamless tubing and chrome-moly steel are the two preferred types used.
This diagram shows the difference between the two types of joints. The greaseable version (top) has less material in the center of the joint, reducing its strength and torque rating. A solid U-joint (bottom) does not require maintenance and is much stronger.
DOM steel is better than OEM steel, handling much more torque, up to 1,300 ft-lbs, and 1,000 to 1,300 hp. DOM steel can be spun faster as well with its higher RPM rating. This is a good choice for any car that does not need a lightweight unit.
The step up from a DOM steel shaft is chrome-moly, which is the strongest material available. Pro Stock cars run it with 3,000 hp. Chrome-moly steel tubing can be heat treated as well, raising the torsional strength 22 percent and increasing the critical speed 19 percent. Steel is heavy, which increases the load on the engine and the length of time the engine needs to get to speed.
Aluminum: This is the most common performance driveshaft material. A lightweight aluminum shaft has less rotational mass and frees up horsepower from the engine, reducing parasitic loss. Aluminum driveshafts are strong but cannot withstand as much torque as steel. Therefore, some custom driveshaft shops do not have “twist” guarantees on aluminum driveshafts. An aluminum driveshaft supports up to 900 ft-lbs, or 900 to 1,000 hp, making it a great lightweight choice for most muscle cars.
Carbon fiber: It is the most efficient, but it is also the most expensive. For up to 1,200 ft-lbs or 900 to 1,500 hp, carbon fiber is a great choice. Carbon fiber driveshafts are not only strong, but have a surprisingly high torsional strength, resisting twisting and reducing the shock factor on the rear end. Carbon fiber also has the highest CS, meaning the shaft doesn’t flex at slower speeds, unlike other component material. With the highest CS factors and the lowest weight, a carbon fiber driveshaft can free up as much as 5 hp over a stock steel driveshaft. When winning is everything, 5 hp might make the difference.
U-Joints
Once the driveshaft is measured and ready to build, there are a few other issues to consider. Phasing the U-joints with the weld-in yokes is an important part of the equation. With every rotation of a U-joint at any degree other than zero, a fourth-order vibration is generated. This shows up as a torsional pulse, which is felt as a significant vibration. By phasing the weld-in yokes to minimize the combined degrees of rotation, any fourth-order vibration is drastically reduced. The weld-in yokes need to be installed on the same plane; they can’t be rotated off axis from one another.
U-joint quality also makes a difference, and not just the brand. U-joint design and its load capacity must also be considered. For most cars, 1310-series U-joints are the typical choice, but for performance applications, the rugged 1350-series joints are preferred. The larger the series number, the larger the trunnion.
Trunnions are the protruding shafts under the caps. Larger trunnions equate to more torsional strength, which makes them more resistant to twisting motion. Changing to a larger U-joint is not a simple task; you can’t just buy bigger joints. All yokes (slip, bolt-on, and weld-in) must match the desired joint size.
Crossover U-joints are also an option, but they tend not to be as strong, and they don’t last as long. However, they do allow a larger U-joint to be mated to a smaller U-joint, or vice versa. For example, a new driveshaft comes with 1350 weld-in yokes, but the car has 1310-sized yokes for the transmission and rear differential. A 1350-to-1310 joint has a 1350 on one side and a 1310 on the other, allowing you to install the driveshaft until the slip and bolt-on yokes are replaced.
Although it can be done, using crossover U-joints is not suggested as a long-term solution. The smaller size breaks eventually.
Additionally, the type of joint (solid-body versus greaseable) is important as well. The Spicer-style, solid-body U-joint comes “lubed for life,” and does not have grease zerk fittings. This makes them a little stronger because they do not have the stress risers created by the opening for the zerk fitting in a greaseable U-joint.
The C2 is the most valuable of all Corvette generations, and it’s also a popular platform for an LS swap. The frame is exactly the same from 1963 through 1982, covering the C2 and C3 generations. The Gen III/IV engines are dimensionally similar to the small-block Chevy engines, which were originally installed in the C2. Therefore, an LS engine swap into a C2 does not require many modifications. Motor mounts are readily available, and most of the other modifications are required for all LS engine swaps.
Here, the body has been separated from the birdcage frame. Although the body does not need to be off the frame for the swap, you have greater access to all components and it makes the process easier.
There are few GM cars more beautiful than a C2 Stingray, from the elusive 1963 split window to the 1967, which many claim to be the ultimate Corvette. Under that fiberglass body shell, however, lies a classic drivetrain and transverse leaf-spring rear suspension, and the dual-arm coil spring does not provide a modern level of comfort. For this Red Line Muscle Cars 1967 roadster, owner Fred and Kim Murfin wanted a classic Corvette but with modern ride quality, performance, and reliability.
Parts Compatibility
The only choice for the drivetrain was an LS1. Swapping an LS-series engine into a C2 Corvette is not routine and is certainly not as common as an LS swap into a Camaro or Firebird. Yet the LS swap into a C2 is much easier because the aftermarket now offers many of the required parts to complete the job. Companies such as Street & Performance, Speed Hound, and others now offer the vital parts you need so you don’t have to fabricate or adapt parts to complete the swap.
Of course, manufacturers also offer other parts, such as motor and transmission mounts. Some are compatible among manufacturer, but some are not compatible. I recommend that you select a kit or buy your parts from the same source because the parts are designed to work together. At least 20 different types of motor mounts are offered for the first-generation F-Body cars. But the aftermarket currently does not offer nearly as many motor mounts for the C2 (1963–1967) Corvette. You do not need all these options to complete the LS swap, however. The key to any LS swap is to avoid adding complications.
A set of Speed Hound C2/C3 Corvette motor mount adapters and the correct oil pan make installing an LS engine in the chassis a simple bolt endeavor. No fabrication of the original body work or extensive modifications are necessary. The factory F-Body oil pan works quite well in the C2–C3 chassis without any modifications. There are lots of choices for aftermarket pans, but the Holley LS swap oil pan is a good fit.
Photo 1: These Speed Hound mounts were bolted to the 2000 Camaro LS1 and then bolted to the original 327 frame stands. The F-Body oil pan worked perfectly in the C2 chassis, and it even clears the Steeroids rack-and-pinion.
2. One issue is the clearance of the water pump heater outlets. They have to be removed and replaced with 90-degree barbs or AN-style fittings.
3. The 4L60E fit the factory transmission crossmember. It was marked for the location of the factory-style mount then the engine and transmission were removed.
4. I recommend using a reciprocating saw with the correct blade to quickly cut through the factory steel frame. You can also use a pneumatic die grinder. But I do not recommend using a plasma torch because it’s very difficult to achieve clean, precise cuts.
5. Use a die grinder to clean up the work area and square off the corners and edges. This modification looks clean and professional.
6. Use a MIG welder on 1/8-inch plate steel and box the area that was cut out. Make sure not to apply too much heat in any one area to achieve ideal weld penetration. The area must be completely welded to prevent any moisture or contaminants from entering the frame, which eventually cause rusting. The crossmember remains strong once the boxing process has been completed.
7. Place the transmission into the chassis and test fit. You must make sure that the transmission and engine maintain the proper angle in the chassis. If the transmission has adequate clearance and lines up properly with the engine, no further modifications are necessary.
The Murfins are not using a T56 manual transmission. Instead, they opted to install a 4L60E automatic transmission in their 1967 Stingray, which is the most common transmission bolted to LS engines from the factory. This choice complicated the installation, however, because most swap kits are designed to use a manual transmission. In order to mount the 4L60E, some chassis modifications needed to be done.
The LS1 engine came out of a 1999 Camaro, complete with the harness, computer, transmission, and accessory drive. Although the F-Body (Camaro/Firebird) oil pan and accessory drive works well in the C2 chassis, the newer, better-fitting A/C and power steering components from Street & Performance replaced the stock components.
Motor Mounts
Speed Hound Performance motor mount adapter plates for the Gen III/IV engines position the engine correctly in the chassis to clear all body and chassis components. These plates do not fit the C2 chassis with parts-store motor mounts. Those cheap overseas brands use thinner metal and that is a problem because they do not quite reach the engine.
However, a set of Energy Suspension polyurethane mounts come with a thick spacer plate that allows the engine to sit neatly on the stock frame stands without any issue, although you may have to grind a little on both the motor mounts and the Speed Hound adapter plates where they bolt together to get the fit just right.
Headers
A set of Street & Performance mid-length headers for the Corvette were added to make everything work. These headers come with the correct flange adapters to mount the exhaust pipe. This roadster runs a set of factory-style side pipes, which do not bolt up to the new headers.
To make this combination work, approximately 1½ feet of pipe was cut off the side pipes (starting at the header flange), and then a custom pipe was bent around the Steeroids rack-and-pinion steering shaft to meet up with the remaining side-pipe exhaust.
There are bolt-on side-pipe kits for LS swaps, but, depending on your adapter plates, they may or may not fit. The factory pipes can be adapted to an LS engine; it just requires a trip to the muffler shop for the final connections.
Transmission Mounting Location
With the engine resting in place, the 4L60E transmission clearly does not fit in the stock transmission mounting location. The C2 chassis was originally a 4-speed car and had a stock welded-in crossmember. In order to set a suitable driveshaft angle and correctly mount the transmission, the crossmember needed to be notched and a support plate welded in. This is necessary because the angle of the rear pinion yoke dictates the angle of the transmission tailshaft, and pinion yoke angle is not adjustable.
The Corvette uses a fixed-position center section for the independent rear suspension (IRS); the pinion angle is relatively fixed as well. It can be shimmed, but in most cases the transmission can be adjusted to match it just as easily. The angle should be between 1 and 5 degrees down on the transmission (the pinion angle should match that in an upward angle): the optimum angle is 2 degrees. A magnetic angle finder is used to determine the angles.
Photo 8: With the fit nice and neat, fully weld the notch. Weld short sections and then move on to minimize warping. Make sure that the welds penetrate the steel for strength.
9. Use a grinder to smooth the fresh welds. The trick here is to remove just the top layer to get a flush seam. If your welds do not penetrate well, there are cracks in the joint and the modification is not strong.
10. You can use some Eastwood Extreme Chassis Black to paint the new mount notch. This specialized paint protects the metal from rust and leaves a clean, durable finish.
A piece of 4 x 3¼-inch angle steel about 8 inches long was used for the notch insert and to fill in the boxed section, making for a nice, clean install. The crew at Red Line Muscle Cars mocked up the mounts, fabricated the mounts, welded in the mounts, and dropped in the engine in a single day, so you could easily do it in a lazy weekend.
Wiring
The LS1 was wired using a pre-made harness from Street & Performance connected to the factory ECM, which had been tuned by Street & Performance. The rest of the chassis was wired with Painless Performance wiring products, including a Phantom Key setup that eliminates the ignition key in favor of a transponder and a push-to-start button.
Fuel System
The fuel system was converted to electric using a Walbro external in-line pump with a C6 Corvette single-output pressure regulator return-style filter. This eliminated the need for a second fuel line from the engine. The factory tank was converted to accept the short return line from the regulator filter, which was mounted under the body near the tank (see Chapter 8).
Shifter
In order to shift the 4L60E transmission, the stock shifter was swapped out for a Shiftworks conversion unit. This maintains the look and feel of the factory shifter with the correct detents for the overdrive automatic.
Brake Booster
One aspect that was a real bear on this conversion was the power brake booster. LS engines are wider than first-generation Chevy small-block engines. A typical 11-inch power booster crowds the coil packs on the valve covers. To resolve the fitment issue, you can install custom mounts and move the coil packs underneath the engine or you can use a smaller brake booster.
The Murfins decided to install a 7-inch power brake booster and a cast-iron master cylinder. In order to clear the Stinger hood, the master cylinder was machined on a mill to remove about 1/2 inch from the reservoir.
In hindsight, moving the coil packs would have been a better option, because the smaller 7-inch brake booster did not afford as much room. Yes, the booster fit, but it was a very tight fit with the coil packs. Also, the plastic engine cover had to be trimmed to clear the booster.
Gauges
The factory Corvette gauges look good, but they don’t work with modern electronic senders. Mechanical sending units could be used on the LS, but that is taking a step backward. For this 1967, a set of AutoMeter Sport Comp gauges with black bezels and red numbers were ordered. Using 5-inch gauges for the speedometer and tach, and 2⅜-inch gauges for the rest, they fit right into the factory bezel with no mods required.
If you just can’t do without the factory look, companies such as Redline Gauge Works can replace the mechanical guts with new electronics using the factory gauge faces.
Performance Mods
The end result of this build was a clean Stingray that has the power to back up the look. With no performance mods beyond the ECM tune, the LS1 can break the tires loose in third gear. The Sharkbite front coil-over suspension and rocker-arm-style rear suspension provide the ride and handling that will give a C6 a run for its money, with better styling to boot.
Set the transmission and engine back into the chassis. When the transmission is bolted to the crossmember and the engine is bolted in place on the front subframe, the bellhousing on the transmission should line up with the engine. If it does not, you need to remove the engine and transmission and additional modifications. In this case, everything lined up nice and neat.
