picture of piston head

Here"s a picture of the piston head with the valve "shadow" marks. I turned the crankshaft back and forth, and it never went above the top of the block...always a mm plus space. This marking can be from something previously wrong? Can it be the valves opening at the wrong time? When I take it in, I"ll ask him about it too.

Here"s another stupid question...the two middle pistons and the two outside pistons run together. I thought each was supposed to be on its own?
 
Ooops, forgot the picture!
a128581.jpg
 
An inline 4 cylinder fires twice each revolution of the crankshaft. For the engine to run with even power pulses, two pistons have to move up and down together and be opposite of two more cylinders. One on power stroke one on intake etc etc. Its not uncommon to see valve marks on pistons due to some carbon build up. Diesel engines valves get very close to the pistons.
 
Have seen this before. Could be a worn wrist pin bushing or bushing honed off center,allowing the piston to come up a couple of thousands. Sometimes hard to detect without removing piston and rod.
 
I don't see any signs of physical valve to piston contact, so maybe I am naive, but I then ask, what is the problem?
 
Yes, there IS a problem, that is NOT normal.

Since both valves are hitting, I would suspect a worn wrist pin bushing. Easy to detect if you rock the engine back and forth and look for delayed movement of the piston.

Is it a 4.2 or 4.4" bore?
 
(quoted from post at 01:49:57 09/16/13) Yes, there IS a problem, that is NOT normal.

Since both valves are hitting, I would suspect a worn wrist pin bushing. Easy to detect if you rock the engine back and forth and look for delayed movement of the piston.

Is it a 4.2 or 4.4" bore?
could be wrong, Bern, but best I can tell from his words (& picture), there is no valve to piston contact. He is simply worried about the black shadows on the piston that correspond to valve location. Poorhunter, please comment further on 'shadows' & physical 'contact'.
 
Regardless of whether the valves actually contacted the piston or not, I can tell you for a fact that what I see is NOT normal on a Ford (I've worked on dozens of those engines). Something inside that cylinder is too close for comfort, and needs to be looked into, in my professional opinion. If a wrist pin or rod bearing is on the way out, now would be the time to catch it.

One thing I would do is measure the valve recession on all the valves. If the valves are all pretty much the same and within spec for recession, I would suspect a bearing going out.

Another very distinct possibility is that what we see is contact damage prior to the last (and very recent) engine rebuild. This assumes of course that the pistons were re-used, which I have done often myself on Fords. Those pistons are very tough.

One more thought: If you think that's normal, why does it show on only one piston?
 
I agree with you 100%. THAT is NOT normal. Wrist pin or bearing is most probably... but I also wondered about the valves.... mabey sticking a bit on that cylinder for one reason or another.

Rod
 
I didn't say anything about normal/abnormal, just that everything shown or said pointed to no physical contact. Yes, odd on only one cylinder. Yes, you have pointed out valid reasons to investigate further.
 
Took the head in this morning. The machinist was
concerned about those shadow marks too. There is also a
corresponding mark on the head that matches the hollowed
out part of the piston. He feels like it is a Rod bearing going
out, but could be prior damage is possible. The valves look
newer to him, so those were replaced, but don't know
about the piston. It doesn't look like the piston was actually
hitting the head, but he'll look closer.

He also said that I can try rotating the crank half way
through the stroke back and forth the check for play in that
piston vs the rest. Any other ideas?
 
Have machine shop check valve recession. If within specs, there can ONLY be a few more possibilities. 1) rod or wrist pin bushing as has already been discussed, 2) too thin of a head gasket (not likely), 3) piston protrusion too high for that cylinder, or 4) valve lash set too tight for only that cylinder (not likely). My bets are on #1.

Is the engine 4.2 or 4.4 bore? If it's 4.4, I have some more info for you on head gasket usage.
 
Bern, thanks so much for sharing what you think. I'm not sure what the bore is, but almost positive it's 4.2. I don't have accurate calipers to measure, but the guy at machine shop will tell me. Right now, everything points to the wrist pin...you're #1 thought. If this is the case, how much trouble is it? Split the tractor is what he thinks. For the love of all that's Holy, I hope not...loader is still on tractor, plus I'm no mechanic.
 
A tape measure is good enough to tell the difference in bore sizes. A 4.2 will be just shy of 4 1/4", and 4.4 will be a little shy of 4 1/2". Please report back if you find it to be 4.4", and I will advise on a head gasket.

Run the suspect piston down half way into the bore and then rock the front pulley back and forth while you watch the piston. There should be no visible hesitation of the piston moving as you rock the crank back and forth. Compare with the other pistons if need be.

If there is a problem, you will need to remove the oil pan. This will require it to be unbolted from the front bolster. You can remove it entirely, or roll it forward a few inches on longer bolts. The choice is yours. No need to split the engine from the trans.

A loader very much complicates things for sure. Depending on the brand, it will likely need to be removed first.
 

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