SL-C Manual: Engine Installation
For a GM LS engine plan to use the bolt-on aluminum engine mount stands shown below. Generally, all crate engines sold by GM have these already installed. Six M10-1.50 x 35mm bolts are required to attach them to the engine block if they aren't already attached to your engine.
See the red arrow in the picture below to show where they attach to the engine block.
Most SL-Cs use solid engine mounts, but it is possible to use rubber or polyurethane mounts to reduce vibrations transmitted to the chassis from the engine mounts.
The engine mounts above mount to the engine mount stands as shown above, and to the provided engine mount assembly that is bolted to the chassis.
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Steel mounting plates are attached at the factory to the chassis to support the rear of the engine via the engine-transaxle adaptor plate as indicated by the lower set of arrows in the photo below. These mounting plates are referred to as the rear engine mounts. Note that this picture shows an early setup for GM LS engines. Note that the front mounts shown in the picture above are an older design welded to the chassis. The new design uses a single, adjustable system that can accommodate most all engine mount positions.
The required hardware is:
- 2 ea. 5/8” UNF x 2” Grade 8. Please confirm length as it depends on adaptor thickness
- 4 ea. 5/8” UNF flat washers Grade 8
- 2 ea. 5/8” UNF nylon lock nuts
When actually installing the engine, most builders find it easier to have it bolted to the transaxle, and install the combination as one unit.
The procedure that follows describes installing the already-assembled engine and transaxle as one unit.
Lower the engine/transaxle unit into the car, and let the front engine mounts rest on the front chassis mounts. Loosely bolt the front mounts in, then attach the assembly to the rear engine mounts as shown in the picture above.
Depending on the transaxle used, there may be a rear transaxle mount that is bolted to an adapter plate welded to the tubular steel cross-member that connects the rear suspension support bars. If that is present attach it to the transaxle and align the entire assembly so that it is square in the car.
Tighten the bolts down and torque to the proper specifications based on the fastener sizes.
Water Pump Modification
If you are using a GM LS engine with the factory water pump, you will need to modify the outlet at the top of the pump in order to clear the chassis.
The water pumps vary slightly between LS3 and LS7 engines. The photo below is of a LS7 water pump. The LS7 style is preferred as it is narrower, and facilitates installation in the chassis.
The top red arrow in the photo below shows the problem area.
Also check that the water pump inlet at the bottom and its hose clears the chassis.
There are several ways to solve the outlet clearance problem. Some builders simply cut off the existing outlet and re-weld it with a 90-degree change in direction.
Others have welded AN fittings after removing the outlet.
The photo below shows an engine with a custom stainless elbow mounted on the water pump. This approach offers the best-flowing solution, since the cut-and-weld solution is likely to cause turbulence in the coolant.
Note that the elbow has a sleeve with a lip welded to it to help retain the hose. This engine has a custom front dress that’s not available from Superlite.
For the inlet there is an adjustable part available from Southern Performance Systems. The pump inlet may not be on their web site; you may need to contact them to acquire this part.
This inlet points down, clears the chassis, and is a bolt-on. Check for clearance with the AC compressor, if one is fitted. This inlet requires the compressor to use the inside set of grooves for its drive belt as it will not clear most compressors that are mounted forward to use the same serpentine belt as the rest of the engine.
As with the outlet, it is also possible to weld on an AN fitting at an angle that provides clearance.
Intake Manifold Modifications
If you are using the GM LS series engines, in most cases you will need to reverse the intake manifold so that the throttle body faces to the rear of the engine. Unlike most engines the LS series is symmetrical and allows this. The photo below shows an engine with the intake reversed allowing the throttle body to face rearward.
To facilitate the reversal of the intake manifold you will also need to relocate the factory GM oil pressure sender as in its standard position it will foul a reversed intake manifold. It screws into the top of the engine next to the intake manifold at the left rear corner of the intake manifold. It can be relocated lower on the block using an oil adaptor.
Alternatively, Katech sells a modified valley cover and oil pressure sender with a custom oil pressure sender adapter to avoid all these modifications. It bolts in and uses a modified sensor boss to keep the factory sender.
If you are not using the Katech cover and adapter, the original boss where the sender was located needs to be shortened and blanked off. It needs be shortened by approximately 20mm so that it does not foul on the reversed intake manifold. You can weld a cap over the boss to blank it off. The boss is located on the valley cover plate, which can be easily removed for welding.
Photo showing the finished trimming and blanking off of the GM oil pressure sender boss on the engine valley cover.
Once the intake is reversed, tighten it in a standard cross sequence to a torque setting of 8-10Nm.
Steam and Vapor Recovery
You may want to bend the coolant bleed tube (or steam vent tube) to point it in the desired direction. The tube is located at the front of the engine. This coolant bleed tube is connected to the coolant header tank. See photos below for before and after photos of one recommended direction to bend the tube. It's easy to break the tube while bending, so take your time, and bend carefully. This step isn't needed if you replace the factory tubes with a steam vent solution like the Kurt Urban Racing one discussed below.
Coolant bleed tube before bending:
Coolant bleed tube after bending:
Alternatively, you can buy adapters that screw into the block and have AN fittings on the other side to run lines to a coolant recovery tank. This has the advantage of bleeding all 4 outlets in the engine. While GM uses only 2 in most cars, mid-engine cars can benefit from all 4 steam vents for ease of bleeding.
Kurt Urban Racing has a kit for this purpose, including all the needed fittings and a billet manifold. Here is a photo of such a system installed on a car:
The open fitting in this picture at the top of the new steam manifold (the small black box) is routed to the coolant recovery tank.
If your car has an LS engine, consider using the factory GM LS7 exhaust manifolds. These two-piece stainless steel manifolds flow almost as well as a dedicated short-tube set of headers, are quieter, and offer real packaging advantages. The factory 01 race car uses them, and used them to win the National Championship in 2011. Here is a picture of a polished set of them for reference:
The factory manifolds are often available on eBay and similar sources for very little money as they are often replaced with headers on Corvettes.
Superlite can make exhaust systems for use with these manifolds. The exhaust systems can have optional catalytic converters and mufflers. They can be ordered to exit out the side of the car, or out the rear of the car.
For most cars, there are packaging benefits to having the side-exit exhausts. These pipes exit just before the rear wheels and have an optional protective carbon fiber plate that attaches to the body as shown here.
Below is a photo of the side exhaust from the inside, showing the location relative to other parts in the engine bay. Note the relatively long muffler which should provide a quieter sound. A muffler with more volume would probably quiet the car down more- this one is relatively ineffective.
Also, note the use of a rubber-fabric muffler hanger to locate the muffler. Avoid using solid muffler mounts as they will eventually fatigue and fail from vibration, as well as transmit more sound to the rest of the car.
Rear exhausts can be custom fabricated or ordered from Superlite. One example is shown here:
This exhaust is built on a car with the race tail. As might be expected, the street tail has a different design for rear outlets. Here is a picture of a rear exhaust on a street tail car:
Note the use of header wrap to reduce temperature. This car also has a set of custom headers, with cats and mufflers, and has a great sound on the road.
In choosing between the race and street tails, note that the street tail has much more room for muffler and exhaust system packaging compared to the race tail.
When mounting the engine, check the clearance between the sump and the engine mount cross brace as shown below. Domestic (USA) GM LS3, LS7 and LS9 crate motor sumps have adequate clearance when used with the factory adjustable engine mount system.
Recently, GM has changed the sump provided with its crate engines, though the engines use the same part number. The new Camaro sumps don’t fit perfectly in the car (they are lower than the original Corvette-style sumps) and so buyers need to be aware of this un-advertised change so that they can source the proper sump.
The following photo shows the dry sump tank hose connections for the LS7 or LS9 or other factory-equipped dry-sump LS engine.
The IN connection is the oil feed for the internal dry sump pump. Oil from the bottom of the dry sump tank should be routed to this side of the fitting. Oil is sucked from this fitting directly to the internal gerotor-style oil pump. This internal oil pump pressurizes the oil, pumps it to the oil filter and then to the engine oiling system, eventually pooling (briefly) in the engine sump.
The OUT connection is the oil return to the dry sump tank. This hose should route to the top side of the dry sump tank where it enters on a tangent. As oil drains from the top of the dry sump tank to the bottom, it is de-aerated, and made available to be drawn back into the engine via the internal engine oil pump.
Oil is scavenged from the bottom of the oil pan thru the scavenge side of the internal oil pump, then pumped through the oil pan passageway to this fitting; it then goes to the dry sump tank where it is de-aerated.
The GM oil pan requires adapters to use AN fittings. These are available from suppliers like Peterson Fluid Products and many others. Please confirm these directions and fitment before starting the engine. In the picture below the adapters are the blue anodized pieces.