By far the most popular engine choice for the Superlite SL-C is the General Motors LS (and now LT)-series engines. These engines are available in iron and aluminum blocks, have a strong aftermarket support, and are very difficult to beat if cost, power output, weight and the availability of crate engines direct from GM with a warranty is concerned. A good primer for understanding the LS series is the Wikipedia entry here.
Here’s a video showing some of the differences between the LS and later LT engines.
The LS-series engines range in size from a 4.8 liter engine found in some trucks and thought to be the best candidate for forced induction, to the 454 CI LSX engine available from GM Performance Parts. The LS7 engine is the most powerful normally aspirated engine GM has yet produced, rated at 505 HP. Also available- and with fitment in the SL-C only when ordered at the factory- is the supercharged LS9, an engine reserved for the Corvette ZR1, with 638 HP. Crate engines for both of these, and most of the entire LS series are available from GM. Aftermarket companies have made crankshafts that allow for longer strokes, and there are sleeved blocks and aftermarket blocks that support larger bores- all of which can produce LS-based engines of 500 Ci or more. With power outputs in the 2500 range as an achievable max, the LS series is able to make huge power when built accordingly. Even street engines with 1000 HP are not unheard of nowadays, with, for example, Nelson Racing engines making a daily driver twin turbo LS engine with 900 HP on pump fuel. There are many sources of complete crate engines from other aftermarket suppliers as well. Some reputable sources are Texas Speed, Late Model Racecraft and many others. Before you buy a crate engine- or any parts, for that matter- check for user experiences so you can be more confident that the product is as advertised, and supported.
The LS engine fits well in the engine bay, but like all powerplants has a few fitment quirks.
Style: The LS7-style water pump is preferred, as it is much slimmer, allowing more room between the water pump and the rear chassis crossmember.
Inlet: The waterpump inlet is often modified or replaced with an AN fitting because it is a very close fit to the chassis.
The waterpump outlet on the top of the waterpump must be modified, as it's discharge sits about 1/8" from the chassis crossmember when the engine is located correctly in the chassis, thus preventing a hose from being attached. Some builders have chosen to weld an AN fitting on the waterpump outlet, others have cut and re-welded the existing stainless tube to make a 90 degree angle. Other choices include a 90 degree 'ell' that is fit into the waterpump outlet such that it can be positioned optimally for the coolant tubing. Here is a picture of an LS7 with a custom front dress and a modified stainless 90 degree 'ell'
A neat feature of the LS-series engines is that the intake manifolds are symmetrical. This means they can be flipped around to re-position the intake opening from the front of the engine where there is limited clearance, to the rear. This is what the current Grand-AM Daytona Prototype engines do when they run GM engines. Note that when you flip the manifold, you will either have to modify the valley cover, or buy another modified cover, as the oil pressure sender boss fouls when the manifold is flipped. Modified valey covers can be obtained from Katech. The oil port on the manifold is shown on the picture.
PCV and venting
For those running a dry sump system, venting is usually inherent to the system- you’ll generally have a fitting from the tank to a catch can with a vent on it. Contact Peterson Fluid Systems or your dry sump system supplier for more info about breathers for LS engines using their tanks.
If you are running a wet sump, you may find that your engine needs additional crankcase venting, especially at higher RPMs. A typical symptom is smoking at cold idle, and an inability to keep spark plugs clean.
One simple way is to use two catch cans as shown here:
Another feature of the LS engines is factory support for engine control systems. GMPP sells complete engine control kits consisting of an ECU with a base tune, a complete engine wiring harness terminated with factory connectors, an electronic throttle pedal, 2 O2 sensors and weld-in bungs, an engine fuse box and some other related parts- basically, all you need to install a new crate engine (or a complete junkyard engine) into the SL-C. These are priced very attractively and make the engine install process as easy as it can be. You need only to connect 12V power, and fuel to fire the engine.
There are also suppliers that make custom versions of these kits that can be custom terminated for your lengths, different tunes, etc. These generally cost more, but support may be better, especially if you are building an unusual engine combination.
Most GMPP controllers with the stock tune have driveability problems when a proper Vehicle Speed Sensor (VSS) is not installed. The symptoms are stalling when coming to a stop, or idle, or other odd idle behavior.
The solution seems to be to either use a suitable VSS, or an aftermarket solution that emulates the desired VSS by using GPS. One known working product can be found here.
Some transaxles don't have a VSS (like the popular Porsche G96 series) and must use an aftermarket solution.
There are some tuners who supposedly have had success without a VSS signal by tuning other parts of the system, but the simplest way to solve the problem is probably the GPS solution discussed above.
Thanks to Mike Sharkey for this info)