What Did I Do? I Built An Engine For My Corvette

I purchased my 1971 Corvette with the specific intent of building an engine for it. Little did I know that it would take almost twenty years to achieve this. The Corvette came from GM’s factory with an L48 350 cubic inch small block making 270 (gross) horsepower.

This equates to approximately 230 SAE net horsepower, which is how horsepower was figured starting in 1972. The previous owner of my Corvette had recently rebuilt the engine before my purchase. It was a numbers matching engine, with the original block, carburetor, intake manifold, water pump, oil pan and bellhousing. The heads were not original, but had the fun feature of leaking oil through the valves.

With the exception of those leaky valves, the Corvette ran strong. Over the years, I acquired new parts for the new engine and put many of these to use on the old L48 engine. The threads on the fuel inlet of the original Quadrajet carburetor were stripped, requiring replacement with a new Edelbrock Quadrajet 1904 carb (they no longer make these). I replaced the points distributor with an MSD tach drive distributor connected to a 6A ignition box and Blaster 2 coil. To save weight, I installed an Edelbrock intake manifold. A weeping water pump brought about a new Edelbrock aluminum unit. The original aluminum radiator was replaced with a Dewitts radiator with an electric fan mounted to it.

New Dewitts radiator in place
New Dewitts radiator in place

The best modification I did to the original engine, by far, was replacement of the heads. These heads leaked more oil than all the oil fields in Texas. New spark plugs would recoil in horror as they were inserted into the oily combustion chamber. As luck would have it, Dad had a new set of Corvette L98 heads. These heads were aluminum, came completely assembled, and had tiny 58cc combustion chambers that raised the compression ratio over 10:1. The car responded amazingly well to these heads. Throttle response was immediate, there was more torque and spark plugs lasted tens of thousand of miles. These heads were part of the reason why I took so long to build the new engine – the old L48 was running great.

I eventually gathered enough parts to be ready to put the engine together. Some of those components are as follows…

  1. Engine block – 4 bolt main 350 block bored to 4.030 (355 cid)
  2. Heads – AFR Eliminator, 195 cc
  3. Intake – Edelbrock Performer
  4. Crank – GM forged
  5. Rocker arms – Crane Energizer 1.6, full roller
  6. Cam – Crane hydraulic roller. Lift: 542 int, 563 ex. Duration @ .050: 222 int, 230 ex. Lobe separation angle: 112°.
  7. Lifters – Crane hydraulic roller
  8. Pistons – Wiseco Pro-Tru forged with floating pins
  9. Connecting rods – Scat forged I-beam
  10. Flywheel – Hays billet, 30 lb SFI 1.1

Action Machine in Shoreline, Washington took care of the machining. They installed the freeze and oil plugs, the cam bearings and provided bolt lubricant and torque specs. The brand new crank needed machining and they took care of that.

The engine went together without drama, though the sixteen year old tired of tightening and loosening the main caps in order to verify proper clearances. In time, this will be good for him. He can tell his grandkids “When I was a kid, we had to torque and loosen the mains seventeen times to install the crank.” His grandkids will roll their eyes and get into their nuclear fission powered hover mobiles to get McRibs (I can’t foresee a future without the McRib).

I brought the engine home from our off-site workshop and let it marinade in the garage while I contemplated the best method to put it back into the car. It seems the C3 Corvette people have figured out that the best way to drop an engine and transmission (I had already connected the two) into the car is to raise the front and remove the right wheel so the hoist has room to maneuver. These Corvette people were correct and the engine dropped into place with only a little finagling of the solid engine mounts. The real time consuming, tedious work then commenced – hooking up all the wiring, running the lines for the new Vintage Air air conditioning system, fuel lines, and then cleaning up all the wiring.

At this point, I should point out that I decided to do several tasks in addition to the engine while it was out of the car. Whether I did this out of some masochistic desire to assure that something would go wrong, or it was just poor planning, I don’t recall. While the engine was out, I installed new carpet and under-carpet insulation, a new stereo, Borgeson power steering, Vintage Air air conditioning and other various interior trim. The new stereo was a result of having lost the face plate on the old Blaupunkt. My wife would tell you that some day I will find that faceplate and wonder where I put the stereo that goes to it. She is correct.

Fast forward to June 9, 2015. The car is ready to start. The new battery is hooked up. I am wandering about the house, killing time before our daughter’s school picnic. I thought “This puppy is ready to start. I should go get some gas.” I filled up the government approved, idiot-proof but almost impossible to use gas can with high octane unleaded, brought it home and dumped the contents into the tank. I filled the Quadrajet with fuel through the vent tube, readied the fire extinguisher (just in case) and jumped into the driver’s seat. I started to crank the engine, not really paying attention because I assumed it wouldn’t start right away. When you watch “Gas Overhaulin’ Garage” or whatever show on Velocity, the cars never start right up. They always forget to install this or that, they blame “Fat Turkey”, or whatever stupid nickname they’ve assigned to that mechanic, they fix the problem and then start the car. My car? It starts right up on the first crank. Because I’m obviously awesome. Or something. I was shocked.

As the engine fast idled, I jumped out of the car and inspected the carburetor fuel inlet for leaks, checked to see if there were any oil leaks and looked under the car to see a slow drip from the fuel pump outlet. A quick tightening of the tube nut took care of that problem. The only problem I encountered while getting the car on the road after the engine build was the vacuum advance canister from the MSD distributor was worn and would not hold vacuum, causing the car to run a little warmer than I preferred since it was providing no advance. A new canister fixed that and the car was back on the road after several years in its stable.

This engine project taught me the importance of finding a good machine shop. I measured everything before putting the engine together and all tolerances were spot on. Another tip that I will use on future projects will be to read and follow instructions before performing various operations. I’ve been reading “How to Build the Small Block Chevy” books for decades. I followed their steps to the letter when assembling this 355. The manufacturer’s instructions for various items were also key to building an engine that started right up and should last for several decades.

Here’s video from the day the new engine started.

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