I have just purchased my first Corvette. The car is matching numbers on all drive train components.

The car has about 120,000 miles and pulls strong all the way to the redline. There is mo smoke. However, that is a lot of miles on the motor.

The motor has lots of oil leaks.

Also, when I do punch it from a dead stop it makes a grinding sound like it has a bad motor mount. As long as I press steadily down on the gas there is no grinding. It just goes.

Should I even consider rebuilding the motor at this point or should I start replacing gaskets to stop the leaks. The heads have never been off this car as best I can tell.

What do you guys think?


Bill Lennox

The motor mounts can be examined while the car is on a lift. When I bought my '78 and had it gone over we found one motor mount was cracked, though not seperated. I have seen other cars with a broken motor mount have the engine revved up and you can see it rise up on one side. Motor mounts can be replaced without yanking the engine.

As far as what to do with your engine otherwise, you need to ask yourself a bunch of questions...how long do you plan on owning the car, budget, etc. If you decide to rebuild the motor, then you need to decide if you want to keep it original, modify it for better performance, etc. I believe most will advise you to keep things original since the car is numbers matching now, but that certainly doesn't stop you from making internal modifications to improve it. You can also install a crate engine and save the original and rebuild it at your leisure and enjoy the new motor.

For now, what you can do is buy a can of Bearin' Seal. That will stop many leaks for the time being until you decide what your long term plan for the car is. It's not a fix, but can help for a while.

Sounds like you bought a nice car. Best of luck and have fun with it.

The grinding sound is what would concern me the most. For peace of mind I would look for that first. The motor still sounds strong. Could the sound be the clutch, posi, or exhaust rattling in the crossmember?

The sound only occurs when I punch it. Frankly I won't be punching it because I do not want to break anything.
However, I still need to fix the problem. Since it pulls strong I am assuming an external problem.

How hard is it to visually inspect the motor mount. There is oil all over since the valve cover gaskets leak. I have the replace gaskets and will take care of the oil leak.

If the car were an automatic it would be easy to hold my foot on the brake while I give her a little gas and watch what happens.

frist thing i would do is degrease it and pressure wash it really good then check the motor mounts and so forth till u find thr problem ,about rebuilding it i would keep it stock and bag it ,put another motor in if you want to make it go fast (and i think fast is the way to go but thats me )that way if anything happins to the motor you have the stock one to replace it with and you keep the value that way !! hope it all works out for you

Thanks rockin!

I think that is what I will do.

Actually I am just gonna put the top down and cruise.

The 350/350 hp with 11:1 compressions runs pretty strong.

If you have a bad motor mount look at the fan shroud. With a bad mount the engine will likely torque enough to have the fan hit the shroud. Scrapes or wear on the shroud will show.

If you decide on a rebuild be careful when they deck it. It could mean the end of your matching number engine when they grind off the numbers. Once gone they can't be replaced without detection.

It then means that you and only those who believe you know it is an original engine. It happens. And it could cost you $$$$$$$

A safe bet would be to change the motor mounts anyway, since time, and wear are detrimental to mounts. Also, if the valve covers leak as bad as you stated, the oil would definately make its way down to the mounts, further degrading the rubber in the mounts.
I have to agree with the fan hitting the shroud when you punch it. This probably would only happen in gear, as the driveline would be a huge load for the motor to pull. Have you tried revving her in park, or neutral? The motor gremlins don't usually make an appearance while you're under the hood paying attention.
Good luck with your baby. Let us all know how you make out with the noise.