VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Head gasket replacement

Howdy,

Would it be common sense that if an engine, in this case a 1935 207 cid, sits for several decades, a replacement head gasket is in order?

Thanks

I wouldnt consider replacing the head gasket for the fun of it. Check that all parts move as they should and there is reasonable compression I would be leaving the head gasket alone, if there is a problem that requires head removal then replace the gasket.
Tony

Thanks for the feedback Tony. What would be considered a reasonable compression, 120+?

I agree with tonyw. Compression tests will be pretty bogus on any engine that has sat a long time. Soak up the rings in penetrating oil or diesel and make sure all the valves move. Run it and drive it for a while before you get too concerned about compression numbers. If there is a dead cylinder, then compression deserves a much closer look.

Evenness it what you want out of a compression test, not absolute numbers. If the variation is 25% or less, I would run it and see if it improves. 120 sounds way high to me, but others will know better what a 207 typically does. Head gaskets are not expected to fail from sitting. Good luck.

Thank you. Engine has been soaking with MMO for a week or so and I hope to attempt to turn it over this weekend and go from there.

I expect that the head gasket will not be the source of low compression if it is low. The main reason to remove the head now would be to inspect the bores before you try to turn over the engine.

If the cylinder bores got dry and rusted the rings will pretty much be ruined when you turn the engine over even with all the soaking. Whatever you use to soak the cylinders will not remove the rust.

It is also possible that the valve faces and seats have corroded for the valves that were open when the engine stopped.

Make sure you soak the valve stems and the pour some down on to the lifters. Remove the valve cover and watch the valve train when you try to turn the engine over. If a valve is sticking you could damage a push rod.

Thanks Rusty, I have done all of which you speak of and I do plan to have the valve cover off when I try to turn the engine over. I know it's not a guarantee, but from what I see under the valve cover on my green dump truck, I am encouraged that this engine will turn with no issues. Now the engine in the white dump truck not so much. There is rust on the head....valves/spring/arms/push rods above the first cylinder.

What Rusty and Bloo have said is correct, low compression is caused by several different possibilities (rusty bore, worn or broken rings, pitted valves or seats, bent or stuck valves). A compression reading of 90lb is about the best to expect from a well used engine and 60lb or less will make the engine very hard to start and not run properly, if compressions vary more than about 20lb from best to worst there is generally 1 of the above problems existing in the lowest cylinder and in most cases the head will most likely need to come off, a stuck valve can be freed without removing the head but often the seat or valve face is pitted as well and bore rusted. With the spark plugs removed the engine should turn reasonably freely by hand (no need to force it) and all valves should open and close without increasing valve clearance or bending pushrods.
Tony

Thanks Tony.