Thread: Broken motor

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Here's a puzzle for you all. This regards a Ford 351W, but the basic question is applicable to any engine.

Engine running very badly; obviously on only seven cylinders, sometimes, six. Pulled the plugs, all showed wet and oily, some worse than others. Compression test showed all cylinders except number one with between 75 to 125; number one was zero, on three consecutive tries. Obviously, teardown time. Got the engine out and on the stand, had chunks of metal of indeterminate origin in the drained oil, and in the pump screen, but no signs of smaller shaving type contaminants, and no fuel in the oil. From the bottom, all looks as it should be, no cylinder scoring, can even see some cross hatching still on the lower cyl. walls, everything looks clean. Pulled the heads; number one looks ok, but the ex. valve is a bit deeper into the seat than most of the others ( a couple of the other ex. valves look similar); the ex. valve RA ball on number 4 is siezed to the stud, and we had to wait to get the pushrod out until we lifted the head off. There is no damage to the tops of the pistons, but all cylinders show oily. There is no scoring in the cylindrs when viewed from the top, and virually no ridge, just the usual carbon "notch". The valley is clean and the cam looks fine, from what we can see. We still have to pull the pistons and crank, but that is going to be a day or two from now.

I'm just sort of "brain busting" here, but my inclination is to suspect a broken second ring in number 1, and leaky rings all around; but, the lack of any cylinder wall damage causes me to want to second guess this assumption. We still have not pulled the timing cover, so who knows what we might find in there?

Will you all offer your ideas of what might be up, here, based on this info? I'd appreciate any and all input.

Well, where can the oil come from?

The oil pasages, from the rings, or from a defect in the block or heads...anywhere else?


With a global problem like you seem to have, I'd suspect a global cause- something common to all of those things

I'm not familiar with the 351W at all, and I don't know the oiling system at all...but you mention some head problems. Does the 351W oil anything through the heads?

With exhaust valves recessed and a valve stuck, is it possible that your valve seals let go all around? or that they were damaged during installation? Just guessing

It might help to know more about the engine itself, and what if anything, has been done to it prior to your problems

Originally posted by Rrumbler


I'm just sort of "brain busting"

Most likely, taken from what you've reported, the problem is wiped out exhaust seats and the oil consumption is probably due to valve guide/valve seal problems.