No compression on one cylinder

well, s*it

wrong again

did excess heat cause this, maybe ?

It is not necessary that oil or water leak anywhere in order for a head gasket to be blown. I have seen this condition result in cutting a slot between cylinders in the block and/or the head in heavily loaded engines which required replacment of the block and/or head to repair. It is also not necessary that the cylinders have equally low compression for this condition to exist. If you bored the engine much when it was built, much of the surface area between the cylinders was removed making correct torque more essential. The fact that it was a sudden loss of compression under heavy towing conditions is not terribly surprising. If it were my engine, I would be either pulling the heads or checking into a replacement engine. With the FE engine, it is likely that the head will need to be surfaced. It is best to mill both heads evenly to maintain relatively even compression in the engine. At some point, it becomes necessary to also mill the intake manifold to maintain proper sealing around the intake ports. A good auto machine shop shoult be able to handle that chore easily.

I would normally expect excessive heat to cause this but the temp gauge did not go above the normal operating range. However, if the sending unit was bad (possible) that could help explain the resulting problem. The machine shop called me a few minutes ago and informed me the head was cracked (very small) between the valve seats which might explain the released seat. Anyway, I have to shell out $475 for a used replacement head, all new valves and other work associated with a head job. Thanks to everyone for your contributions. All very interesting.

compression,

guys...what

I guess anything is possible but I've never heard of that one before. However, I did see a friend lose a bet on whether or not a spark plug gap would increase when tightened in the cylinder. Your guess?

compression,

A spark plug will stretch just like an overtorqued bolt will, changing the gap.

After 35+ years of wrenchin', i thought i had heard every BULLSHIT story in the book. I guess not.

I think I'd like to see this 1st hand.. Anyone got a head off an engine they'd be willing to experiment with? Set the gap on a plug, then install it using proper torque and measure it again. Then overtorque it and measure once more.

I don't see how the gap could change..

I'm surprised that after 35+ years of wrenchin', you've never seen a stretched bolt. Maybe you were just never a good enough wrench to notice. H

Or just maybe he's good enough not to stretch bolts that weren't meant to be stretched......... In my opinion anyone who over torques spark plugs enough to significantly change the gap should have there tools taken away Bob

It's not as difficult to understand as one might think. Had I not witnessed it first hand many years ago I would not have believed just how much the gap did increase. Think of it in practical terms. The threaded portion of the spark plug is simply a hollow pipe with an "L" shapped electrode at the very bottom. It is much easier to stretch the threads of a hollow pipe than it is a solid bolt. The center electrode is held rigid by the upper portion of the spark plug seated against the plug opening. Once torque is applied to the upper portion of the plug the threads attempt to track further into the female threads of the opening. This creates a stretching of the "pipe" portion of the plug and efficiently and assuredly increases the gap in the plug. The increase is, although slight, much greater than you might expect. Find a loose head and see for yourself. A torque rating of 30 to 35 ft lbs will do the job. Our subsequent trials showed that a plug with fewest threads produced the greatest increase.

Don't bet any serious money on this one Steve, cause you'll lose. See the post below.

I think education is a better alternative, at least for those willing to learn. H

You'll never catch engine damaging heat build up found during high load intermittent use (pulling a grade) by relying on the coolant temp gauge, takes too long for the coolant to increase in temp and when it does damage could already be done, or worse, you won't see any temp warning at all (like in this case). Install a cyl head temp gauge, I wouldn't fly in any plane that did not have one.