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Car Craft Mag
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Engine Swap: One Piece or Two?
Chris Schwarz; Dunlap, IL: I have a question about swapping a one-piece or a two-piece rear main seal Chevy small-block engine. I have a ’98 Chevy K1500 truck with the stock Vortec 350, which is getting tired. I also currently have a pretty mild 383 built from a ’70s-era block in my’85 Monte Carlo that I built while I was in college. The 383 is a two-bolt main running a cast Scat crank, Speed-Pro hypereutectic pistons, a mild Crane cam, and cast-iron Vortec heads. I have a good job now and can afford to build something stupidly fun for the Monte Carlo but don’t think modifying the 383 would be worth it. It runs perfectly fine and would work well in my truck. What parts would I have to change to put the 383 in the truck? I assume I would need a new flywheel (the truck has the NV3500 manual transmission). Also, what needs to be done to put the truck’s fuel injection and accessory-drive system on the 383?
Jeff Smith: As you’ve anticipated, the engine swap is relatively easy in terms of physically adapting the engine to the truck, and even the serpentine accessory drive will cross over, but I think the conversion of the TBI would be disappointing. Let’s hit the easy things first. Yes, you will need a new flywheel because the Vortec small-block is a one-piece, rear-main-seal engine, while your ’70s-vintage 383 is based on the earlier two-piece, rear-main-seal version of the small-block Chevy. I will assume that because the Scat crank is cast, it is externally balanced. This means you will need a 400-style externally balanced flywheel for the engine swap. Since you will be bolting this engine into a truck, we’re going to also assume that the truck’s five-speed will not work well for a performance application. This means you’re not going to abuse the truck with lots of high rpm. If that’s true, then you could get away with a non-SFI–style flywheel, which will be less expensive, though I would recommend at least nodular (rather than cast) iron. Better still is a steel flywheel, but it doesn’t have to be SFI. Cost is directly related to better materials, with the cast iron being the cheapest, then nodular iron, then steel, and finally an SFI-spec’d steel flywheel.
The accessory drive should bolt right on as long as the heads on your 383 have the accessory boltholes. That serpentine system bolts directly to the block and the heads and does not connect to the water pump, which is nice when it comes to swapping water pumps. This leaves us with the TBI injection. This system will be too small for a 383, unless you don’t mind that the engine won’t make 300 hp. Frankly, the TBI is undersized even for a 350ci engine. Even if the 383 has a stock cam and heads, the TBI throttle-body will be a cork at around 480 cfm. There are ways to marginally improve the airflow, but doing so would only aggravate the even more constricted fuel delivery, since with only two small injectors, fuel pressure is limited to 15 psi. From an emission standpoint, you’re not supposed to change things, but Illinois is thankfully less overbearing than California. You could use a Tuned Port Injection (TPI) setup if you’re only going to spin the engine to around 4,500 rpm. The TPI would deliver some fantastic torque—just not horsepower. If this sounds plausible, you could easily adapt FAST’s EZ-EFI to the TPI package. The universal EZ-EFI adapt kit (PN 302000, $891.95, Summit Racing) is affordable, but you will need 28-lb/hr-or-larger injectors for the 383 to flow enough fuel to make 375 hp. Another suggestion for your engine swap is the super affordable MegaSquirt. If you are willing and/or capable of soldering together your own mother board, you could assemble a complete system for around $400, and there are tons of people on the Internet with MegaSquirt experience. The least expensive approach would be to control just the fuel and use a separate ignition like an HEI distributor. There are more complex MegaSquirt systems that also control the ignition, much like a GM system, using a GM HEI small-cap distributor. This isn’t an emissions-legal EFI package, but functionally, it is very close. This could cost almost the same as the EZ-EFI system if you dial up the most complex MegaSquirt. But if you can accomplish the DIY thing and solder up your own system, you can keep the engine swap cost down to around $400–$500. That’s about as cheap as you can get and still call it EFI.
Fuel Air Spark Technology (FAST)