Did I ruin my C3?
Thread Starter
3rd Gear
Joined: Jun 2026
Posts: 4
Likes: 0
Did I ruin my C3?
I am trying to fix up a 1980 Corvette 305 engine. I replaced the intake manifold gasket since it was leaking oil. I tried following many videos on how to complete and being as careful as possible. I also removed the emissions equipment while I had everything off. After reassembling the car, I turned it on and revved the engine. I heard a loud noise, and the engine turned off. I noticed coolant leaking over the starter. I drained the coolant and disconnected the battery. I have not touched anything else. I read on old threads that I possibly hydro-locked it, and it could have caused severe damage. I am going to have it towed to a shop, but I wanted to know how it could have happened, whether the engine is ruined, and if there is anything else I should do to the car to minimize damage before going to the shop?
If anyone has any experience with this, please let me know.
If anyone has any experience with this, please let me know.
Le Mans Master
Joined: Jan 2001
Posts: 6,748
Likes: 1,390
Vettenovice952
Don't change anything else and take a bunch of pictures with good lighting.
IF you broke something where the water came out then you should be able to locate that leak (or rupture) by adding water back.
Go search for and see you see that. Also, check the oil to see if it has water it.
No need to freak out just yet.
BUT a question: How did you set your timing after putting everything back together?
Don't change anything else and take a bunch of pictures with good lighting.
IF you broke something where the water came out then you should be able to locate that leak (or rupture) by adding water back.
Go search for and see you see that. Also, check the oil to see if it has water it.
No need to freak out just yet.
BUT a question: How did you set your timing after putting everything back together?
I am trying to fix up a 1980 Corvette 305 engine. I replaced the intake manifold gasket since it was leaking oil. I tried following many videos on how to complete and being as careful as possible. I also removed the emissions equipment while I had everything off. After reassembling the car, I turned it on and revved the engine. I heard a loud noise, and the engine turned off. I noticed coolant leaking over the starter. I drained the coolant and disconnected the battery. I have not touched anything else. I read on old threads that I possibly hydro-locked it, and it could have caused severe damage. I am going to have it towed to a shop, but I wanted to know how it could have happened, whether the engine is ruined, and if there is anything else I should do to the car to minimize damage before going to the shop?
If anyone has any experience with this, please let me know.
If anyone has any experience with this, please let me know.
Last edited by carriljc; Jun 15, 2026 at 05:55 PM.
Thread Starter
3rd Gear
Joined: Jun 2026
Posts: 4
Likes: 0
Vettenovice952
Don't change anything else and take a bunch of pictures with good lighting.
IF you broke something where the water came out then you should be able to locate that leak (or rupture) by adding water back.
Go search for and see you see that. Also, check the oil to see if it has water it.
No need to freak out just yet.
BUT a question: How did you set your timing after putting everything back together?
Don't change anything else and take a bunch of pictures with good lighting.
IF you broke something where the water came out then you should be able to locate that leak (or rupture) by adding water back.
Go search for and see you see that. Also, check the oil to see if it has water it.
No need to freak out just yet.
BUT a question: How did you set your timing after putting everything back together?
I followed a video I watched, and I marked the intake manifold and wall with the angle of the distributor. I then placed everything back as they were using the markings. I did not set the timing myself. Would this have caused the issue?
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,205
Likes: 4,295
From: US-PNW
What kind of noise was it?
I think first you want to see if the engine damaged a valve, piston, or rod. Remove all the spark plugs and, using a socket and long bar on the crankshaft bolt below the fan, see if you can roll the engine over two full rotations. If you have coolant in a cylinder this should also force out any puddle of significance, so examine the spark plug holes and sides of the block below for coolant.
I'm not sure you can see coolant on the dipstick if it's a small amount unless it ran long enough to mix the fluids into a coffee w/cream color. The oil will float on the coolant so you'll only see a small bit of added volume in the pan - maybe too small to see. You can drain off a quart from the drain plug to see if any coolant entered the oil system.
I think first you want to see if the engine damaged a valve, piston, or rod. Remove all the spark plugs and, using a socket and long bar on the crankshaft bolt below the fan, see if you can roll the engine over two full rotations. If you have coolant in a cylinder this should also force out any puddle of significance, so examine the spark plug holes and sides of the block below for coolant.
I'm not sure you can see coolant on the dipstick if it's a small amount unless it ran long enough to mix the fluids into a coffee w/cream color. The oil will float on the coolant so you'll only see a small bit of added volume in the pan - maybe too small to see. You can drain off a quart from the drain plug to see if any coolant entered the oil system.
Race Director
Joined: Mar 2017
Posts: 11,971
Likes: 4,522
From: Virginia
Think of it instead of creating an opportunity! Unless you live in California, you are now free to replace the worst engine GM ever put in a C3 with something much better. You can ditch the computer controlled carb and dist at the same time.
Please post some photos without the air cleaner assembly. Perhaps someone already did that second step.
Please post some photos without the air cleaner assembly. Perhaps someone already did that second step.
Drifting
Joined: Feb 2013
Posts: 1,474
Likes: 379
If you didn't turn the engine after pulling the distributor you could not have hurt anything to bad, maybe a tooth off as someone stated. but if you adjusted the valves you could have more problems. What it sounds like is a backfire and the timing is off . I don't see how you could hurt anything. You need to get the engine to top dead center and see where the rotor is pointing
Last edited by socal_tom; Jun 15, 2026 at 11:26 PM.
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,618
Likes: 7,068
From: New Or-leens Loo-z-anna
Did your engine crank and idle normally before you revved it up?
The engine usually wont crank over or it will turn over very slowly if hydrolock happens.
Once the cylinder that is full of coolant reaches the compression stroke is when the hydrolock occurs.
I hydolocked my engine once but quit trying to crank it once I heard the starter bog down. The problem turned out to be a tiny 1/8" diameter flat washer between the intake gasket and head allowed coolant to leak into the cylinder near the flatwasher.
The engine usually wont crank over or it will turn over very slowly if hydrolock happens.
Once the cylinder that is full of coolant reaches the compression stroke is when the hydrolock occurs.
I hydolocked my engine once but quit trying to crank it once I heard the starter bog down. The problem turned out to be a tiny 1/8" diameter flat washer between the intake gasket and head allowed coolant to leak into the cylinder near the flatwasher.
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Race Director
Joined: Mar 2016
Posts: 14,446
Likes: 8,243
From: Napa Valley California
I post #1 you stated that you replaced the intake gasket.
Did you just replace one intake gasket or all the intake gaskets?
How long did the engine idle and how was it idling before you revved it?
How high of rpm did you rev the engine to and for how long?
Post pictures and check the items suggested above, then report back before towing it to a garage.
Did you just replace one intake gasket or all the intake gaskets?
How long did the engine idle and how was it idling before you revved it?
How high of rpm did you rev the engine to and for how long?
Post pictures and check the items suggested above, then report back before towing it to a garage.
Thread Starter
3rd Gear
Joined: Jun 2026
Posts: 4
Likes: 0
I post #1 you stated that you replaced the intake gasket.
Did you just replace one intake gasket or all the intake gaskets?
How long did the engine idle and how was it idling before you revved it?
How high of rpm did you rev the engine to and for how long?
Post pictures and check the items suggested above, then report back before towing it to a garage.
Did you just replace one intake gasket or all the intake gaskets?
How long did the engine idle and how was it idling before you revved it?
How high of rpm did you rev the engine to and for how long?
Post pictures and check the items suggested above, then report back before towing it to a garage.
The car was idle for about 5 seconds or less. I started but stumbled and died, no weird noises. Which I thought was normal for a car sitting for a couple of days. After starting it a second time, I gave it a little gas up to 1000rpm. As the RPM was dropping, it made a knock, and the engine died.
I had to go into work, so I haven't had time to check for bent rods yet. I will update today with the extent of the damage later today.
Race Director
Joined: Mar 2016
Posts: 14,446
Likes: 8,243
From: Napa Valley California
You bought the car to learn.
Now you are learning and will have more knowledge as you move forward.
What ever you do, it doesn’t hurt to post pictures and ask questions.
You we’re smart by letting it idle and just increasing the rpm a little bit.
Keep asking questions, we are here to help.
I’ve been around cars, boats and motorcycles all my life and learned a lot over the years.
My 73 build project is my first Corvette and I knew nothing about these cars when I started.
I’ve learned a lot about this car but I know nothing compared to some of the guys and gals on this forum.
I ask a lot of dumb questions, trust me I do!
Now you are learning and will have more knowledge as you move forward.
What ever you do, it doesn’t hurt to post pictures and ask questions.
You we’re smart by letting it idle and just increasing the rpm a little bit.
Keep asking questions, we are here to help.
I’ve been around cars, boats and motorcycles all my life and learned a lot over the years.
My 73 build project is my first Corvette and I knew nothing about these cars when I started.
I’ve learned a lot about this car but I know nothing compared to some of the guys and gals on this forum.
I ask a lot of dumb questions, trust me I do!
Melting Slicks
Joined: Feb 2018
Posts: 2,331
Likes: 725
From: Marietta GA
I can tell you honestly that you aren’t the first person to install head gaskets on BACKWARDS. While in high school a buddy and myself replaced the heads on a friend’s 327 Chevy, he paid us $ 10. Needless to say we had to repeat the job, and even buy a NEW Set of head gaskets. It’s easy to guess why I never became an auto mechanic? Oh, it was in the winter, and the car was parked outside. 😬😬😬
Race Director
Joined: Mar 2017
Posts: 11,971
Likes: 4,522
From: Virginia
Hopefully you'll be back on the road soon, and no permanent damage was done.
If you insist on continuing to learn about Gen 1 SBCs, pick up a copy of David Vizard's book. (This is an updated book, the one I have is now out of print and $300-!).
Or, you could take this opportunity to do what GM did, learn from 40 years of development, and pivot to to the Gen III or Gen IV LS engine platform instead.
There is zero coolant in the intake of an LS engine, and the amount of RTV silicone used to assemble it is equivalent to a day's worth of toothpaste. It goes together like LEGOs, and gives you EFI and a roller cam for free!
If you insist on continuing to learn about Gen 1 SBCs, pick up a copy of David Vizard's book. (This is an updated book, the one I have is now out of print and $300-!).
Or, you could take this opportunity to do what GM did, learn from 40 years of development, and pivot to to the Gen III or Gen IV LS engine platform instead.
There is zero coolant in the intake of an LS engine, and the amount of RTV silicone used to assemble it is equivalent to a day's worth of toothpaste. It goes together like LEGOs, and gives you EFI and a roller cam for free!