Piston access without engine removal?

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Jul 31, 2025 | 08:46 PM

d0m

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Piston access without engine removal?

Hi everyone, I recently bought a 1984 corvette, it’s been sitting for 25 years in a garage so I’ve done the needed service, however it’s locked up due to sitting. Oil was fine so I know it’s due to storage. Manually cranking it, even with good force on a breaker bar it doesn’t turn. And I am using the special adapter that fits onto the harmonic balancer via the 3 bolts! I’ve added a shot glass worth of marvel mystery oil to each cylinder through spark plug hole, and I’m gonna wait 6 days to try to turn it manually. If the rust inside the cylinders is bad enough maybe the oil won’t help, and I’ll have to access the cylinders and clean it off. Is there any way to pull the heads off and access the cylinders/pistons directly without removing the engine? This is just in case the oil doesn’t work! Thanks guys, it’s been in a garage this whole time so I’d be surprised if the rust was THAT bad, or if there’s even any. Pulling the heads off would show me for sure.

Jul 31, 2025 | 09:42 PM

Whaleman

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From: LeClaire Iowa

If it is that locked up the rings are for sure rusted but more important the cylinder itself is also rusted and most likely pitted. While the rings might clean up by running the cylinder will not. When you get the heads off and it is still rusted solid then what do you do? I bet you got a good deal on the car. Might need to be thinking it might need an overbore. Dan

Jul 31, 2025 | 10:05 PM

d0m

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Quote:

Originally Posted by Whaleman

I got a decent deal, paid $2400 for it. 93k miles, bad trans, but I got a good deal on a trans for it that I have sitting around, but the more important thing by far is getting it running. I saw someone free up a small block Chevy v8 using loads of penetrant and reconditioning the cylinder walls, so I was thinking I’d do something similar. Removing the heads would also verify what the cause was - maybe there’s something hidden that isn’t rust related? If I take off the heads and there isn’t rust, then I’ll know it’s something more serious. If there is rust then I’ll know I need to clean up the rings and cylinder. I just don’t want to have to remove the engine, so I’m wondering if I can take off the heads without doing that

Jul 31, 2025 | 11:01 PM

s carter

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From: New Port Richey FL

Pulling heads in the car is very possible, as for freeing up I have heard of people using a 50/50 mix of either Marvel mystery oil & Acidtone or ATF & Acidtone
, Letting it sit for days.
If you have access to an air compressor and compression tester you can charge the cylinders with air for a little assistance trying to spin it, you will have to back off the rockers to close any open valves

Aug 1, 2025 | 06:28 AM

Whaleman

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From: LeClaire Iowa

I don't know any way to "recondition" a pitted cylinder wall except an overbore. Dan

Aug 1, 2025 | 08:11 AM

jmeyer58

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From: Mt Prospect IL

2025 C4 of the Year Finalist - Unmodified

Before pulling the heads why not use a endoscope like this to check the cylinder condition.

Limited-time deal: Endoscope Camera with Light, 4.3" Inspection Camera, 1920P HD Borescope with 8 LED Lights, IP67 Waterproof Snake Sewer Tools, 16.4ft Semi-Rigid Drain Endoscope Cool Gadget (Green) https://a.co/d/5hwncOL

faster and will let you know if you need to pull the motor.

Aug 1, 2025 | 11:45 AM

d0m

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Quote:

Originally Posted by jmeyer58

This is a great idea! Thank you

Aug 1, 2025 | 12:22 PM

IHBD

Melting Slicks

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From: So Cal

2023 C4 of the Year Finalist - Unmodified

Quote:

Originally Posted by Whaleman

I don't know any way to "recondition" a pitted cylinder wall except an overbore. Dan

In a $2,400 car, who cares if a bore or two is "pitted"? It will run. The severity and depth of the pitting may affect oil consumption and blow-by, but if the cyl wall surface roughness isn't so excessive as to cause plug fouling, again, who cares?

He wants to get it running as a step to asses what direction his project should take. If he can free it up, and it has enough compression in enough cyls, it will run. Maybe not well, but it will run.