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How to Convert a 350 Into a 383 Stroker

by Richard Rowe

The Chevrolet small block has been around for longer than most people have been alive, as has the 383 stroker conversion. The first 383s were 350 small blocks with a 400 small block crankshaft and rods. The 400 crankshaft required only some minor machine work to fit into the 350 block, and would immediately boost power and torque by about ten percent from idle to redline.

Purchase and install a 383 stroker crankshaft, rod and 10.5-to-1 piston set. The 383 stroker became more popular than the larger-bore 400 because the 400 block had fairly thin cylinder bores. These thin bores caused many a 400 small block to overheat; the overheating cracked the cylinders and junked the block, leaving only the crankshaft intact for sale to 383 builders. The very thing that made 400 cranks so common 30 years ago makes them uncommon today, so you're unlikely to find a 400 core cheaper than a new aftermarket stroker kit that has already received the requisite machine work.

Install a set of four-bolt steel main caps over the center two crankshaft mains if you're using a two-bolt-main block. Have the block align bored and have the cylinders bored 0.030-inch over. This overbore isn't so much to buy you more displacement as it is to help enhance airflow to feed the extra cubic inches. Coat the piston tops with thermally-insulating ceramic powder coating to build power and reduce heat transfer.

Install a set of ported L31 Vortec cylinder heads. You can do the port work yourself or farm it out to a shop, but you'll at least want to gasket-match the intake ports, smooth the valve seat ridge in the bowl area behind the valves and reduce the short-side turn (where the port starts to bend down toward the valve) to enhance low-RPM airflow into the chambers. Coat the insides of the intake and exhaust ports and combustion chamber roof with ceramic powder coating.

Install a stock 1988 to 1989 Corvette L98 camshaft designed for the tuned-port injected (TPI) 350. This cam is actually far too tame for a 383, but installing a set of 1.7-to-one roller-tipped rocker arms will open the valves about 6.5 percent further. This will almost compensate for the 9.5 percent increase in engine displacement; the port work you performed on the already high-flowing Vortec heads will more than take care of the other three percent increase in displacement.

Install a Vortec-to-carburetor-conversion intake manifold and a 600 cfm carburetor. Install a set of full-length, ceramic-coated headers with 1.5-inch primaries and a GM HEI distributor with multiple-spark discharge ignition box. Install a reverse-flow water pump and install the head-venting tubes on the back of the Vortec heads.

Tips

  • An engine built to this spec should produce about 340 to 360 horsepower at a usable 4,800 rpm and an Earth-moving 425 to 450 ft-lb of torque at around 3,000 rpm. This fairly mild engine's fat power-band, efficient combustion, glass-smooth idle and low coolant temperatures (due to the Vortec heads and ceramic coating) make it a perfect fit for a daily-driven muscle-car or truck.
  • Bear in mind when ordering your pistons that the Vortec heads use a 64-cc combustion chamber.

Items you will need

About the Author

Richard Rowe has been writing professionally since 2007, specializing in automotive topics. He has worked as a tractor-trailer driver and mechanic, a rigger at a fire engine factory and as a race-car driver and builder. Rowe studied engineering, philosophy and American literature at Central Florida Community College.

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