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Corvette Overhaul: 383 Stroker

The Corvette, now at least driveable and with definitive proof it was being fueld properly and surviving, was driven by me for a few months, but persisted to nag at me. The need for race fuel was a giant headache, and made it impossible to go beyond a half tanks distance from my house safely. Running it on too low an octane fuel would cause detonation, possibly to probably resulting in internal engine damage. Add that to the fact that at 8mpg and roughly $12 for a mixture of race and pump gas the car cost $1.25/mile, the whole thing seemed ludicrous. It would cost me $20 just to drive to a breakfast diner down the road and back, and that's before I'd even had a bite to eat!

No wonder my father avoided it for so long. Even with it fully sorted it was a giant headache. He'd gotten in over his head in the wrong direction with the build.

I began to speak with the guys over at Granite Stat Dyno again, attempting to see what their thoughts were on getting it off of race gas and back onto pump gas. All sorts of silly ideas came to mind from searching the internet, like methanol injection or simpler ideas like putting on aluminum heads. Finally after a few rounds of silly questions, we came to a deciscion. Pull the heads on one side of the Corvette, take a bunch of measurements, and see just what the hell is going on. We agreed to pull the head from the side of the engine with the one low compression cylinder, so we could see what was going on there, along with investigating what was going on.

It wasn't long before I got the phone call. They'd pulled the head, and before they'd even bothered measuring it was obvious the cylinder with the low compression was in far worse shape than we'd though. The original engine builder had not done the piston ring end gap correctly, which had popped off a piece of the piston, marred the cylinder walls, and caused notable damage. They were surprised it ran at all and have no idea how it had the compression it did, but it was not worth investing in further.

This brought me to a new issue. I now had a corvette with an engine not worth reassembling. It needed a new engine, there was simply no way around it.

After much investigation into engine options, it was recommended to me that we get a reputed engine builder to build a 383 stroker out of the engine block. We could reuse some components to help reduce cost and build a monster of an engine. The price was notably expensive, but it would ensure the Corvette was sorted for many years to come. It would run on regular pump gas, it woud produce more power, and would see better mileage. Seemed smart enough to me, and while expensive in cost, would ensure everything drive train related would be ensured for quite some time.

It took forever for the engine to get completed. The vendor took their time, I had to pull in extra freelance work to cover the engine... but finally 7 months later, it was completed. The engine was bench dyno'd and broken in (click here to see the bench dyno numbers), put in the Corvette, dyno tuned in the corvette and was now the powerful monster everyone had thought it was under my fathers ownership. The corvette, had come full circle and was now a complete beast, as far as the drivetrain was concerned.


The Corvette put down 422ft/lb of torque and 402 horsepower on the bench dyno, which are some pretty darn solid numbers. Pretty much all new cars doe their horsepower rating at the crank, so we can go off of that number for comparison to cars without actual dyno sheets. The dyno sheet, in my experience with sport bikes, always tells the truth. It shows your air fuel mixture, what the power curve is like, what it does where, and if you've got a bench dyno you can tell just how much is lost to the power train.

 

The Corvette put down 316rwhp, and 356.1 torque, yielding a pretty solid torque curve. I'll need to do some further driving testing to see if the accelerator pump is off, but the dip in the bottom with that big initial power dip being so low says to me they didn't configure the accelerator pump right... but this is something I can tool with myself.

Now, compared to the old engine, we've made some serious gains. From 240rwhp to 316rwhp, and 263ft/lb of trque to 356ft/lb of torque. Notable gains were obviousl made, especially in the torque category accross the whole rpm range. This is a streetable amount of power, with as much getup and go as the current chassis and tire setup can even put down to the ground.

The Corvette is now in a place where I can continue the build process!