Swapping a Big Block Chevy Engine

Enclosed is a discussion of our BB swap, if it benefits anyone in the group.

I read several articles on the project including one from a 1982 Car Craft (CC) that was somewhat helpful. I made the swap in early 1992, so I'm a bit foggy on the details. Anyway, here is what I used:

MOTOR MOUNTS:. CC recommended new engine brackets. I bought engine brackets the tune of $50 from GM, but I never used them, as the ones from the Monte worked fine. Originals off the BB engine bolted to the original motor mounts on the chassis. I really do not know if you need new mounts, unless yours are tired. The later (perhaps 1972 on?) motor mounts have an interlocking tab to keep the two parts of the mount together if the rubber cushion deteriorates. I had replaced mounts when the SB was still in the car, so I kept those. Everything dropped right in. To view more information about the various motor mounts in play, read the Motor Mount article.

You should use some sort of strap or chain between the left side of the engine and the frame. If the mounts break, supposedly you can roll the engine over in the frame from torque. I used a bracket and metal cable a friend gave me from a late 1960's BB Impala, but a piece of chain would work as well. You need a bit of slack. I bolted it to the head and wrapped it around the upper a-arm support.

REAR CROSSMEMBER: The TH-400 crossmember is different from the one for the TH-350. However the TH-400 crossmember is, or was, still available from GM, or you could probably find one in a salvage yard hooked to a Camaro or a Pontiac T/A. All of our old used stuff in Minnesota is so rusty here that I didn't bother to look for one. New crossmember cost is about $50 to $75. It bolts right in. I used the trans mount from the TH-400 to attach the trans.

TRANSMISSION & SHIFTER: We used a B&M Megashifter. The column shift is lever operated, so with that removed we used the B&M cable operated floor shift unit. We also used a steering column for a floor shift car. (Not required). Most any automatic transmission aftermarket shifter will work, but the B&M bolted into the 1973 console we were using.

The TH-350 torque converter was used with the TH-400, to give about 500 RPM higher stall. It requires a gas pedal actuated kick-down switch, which the Monte furnished. These are on any TH-400 car or truck, as the TH-350 is rod actuated and the TH-400 is electrically actuated.

EXHAUST MANIFOLDS: Originals were used with no clearance problems. I had some short sections of exhaust pipe made to connect the manifolds to the existing pipes, as the small block pipes curve to the manifolds a little further back in the car. The car had a relatively new 2 1/2 inch exhaust system with turbo mufflers and a crossover pipe. It now sounds powerful but very quiet. I recommend the crossover pipe. It quiets down the engine and allows you to use less restrictive mufflers without objectionable noise.

RADIATOR: I used the original radiator and shroud with a new fan clutch. So far, I've had no cooling problems. If I did, I'd use a radiator from an A/C car.

OTHER: The driveshaft needed to be shortened several inches and while it was out, I had it balanced. Cost to shorten and balance was about $100. I used the driveshaft from the Monte, as it was quite a bit bigger and stronger. When this drive train was in the Monte Carlo, it went through u-joints frequently. I am putting in a driveshaft loop now, although we have not broken anything yet.

The throttle cable had to be shortened by about 1 inch. A Chevy HEI distributor was added.

The rearend from the Monte Carlo was changed from coil spring to leaf spring mounts and bolted in using the original emergency brake cables. You will definitely need traction bars.

I think that was about it. Not too bad a swap. It would probably have taken a long weekend or two to accomplish, not counting time to fabricate the exhaust. We detailed the engine compartment before reinstalling, so it took me longer. I am really pleased with the way it turned out. After selling some of the Monte parts, We ended up with under $700 invested in the drivetrain, wheels and tires, and maybe $150 to $200 in the odds and ends of parts.

Get back to me with questions... have fun!


Last updated: 10/20/2011
Author: MadMike Maciolek

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