The 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.
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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.
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 con-figuration, and the same pattern continued in production through the second-generation small-block: the LT1 and LT4 engines.
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.
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 reengineering.
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.
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.
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, Hon-das, 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.
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 cross-member, 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.
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.
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 buck-ling under the weight.
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.
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.
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 drive-line angles and keeping the tailshaft square between the frame rails.
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.
Choosing a Driveline
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?
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.
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 drive-shaft is not good enough for any-thing 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.
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.
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 predetermined 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.
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.
The composition of the drive-shaft 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.
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.
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.
Feature Vehicle: 1967 Corvette C2 Stingray
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 fiber glass 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.
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.
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.
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.
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 11/2 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 fi t 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.
A piece of 4 x 31⁄4-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.
The LS1 was wired using a premade 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.
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).
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.
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.
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 23⁄8-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.
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.
Written by Jefferson Bryant and Posted with Permission of CarTechBooks