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Hello - I'm rebuilding my 7.3 idi and need some advise regarding the pistons. After pulling them out, cleaning and inspecting, I found the following issues with 5 of them. On the piston crown at the edge of the piston, just adjacent to the pre-comb dimple there is some pretty serious pitting that has resulted in a 'dimple' of sorts on the edge of the piston. I'm not sure if this is normal for an idi with 120k on it.
My question is, is this a problem where the pistons should be replaced? Or is this normal behavior for this engine?
Thanks for all the replies - I ran the worst piston down to my machine shop this am and they also said it's fine to run.
Interestingly, this is a NA engine, not a turbo so I'm not sure why the egt's would've been a problem.
I just bought this engine about a month ago as a replacement. I did a compression test and it had a couple low cylinders. The engine had been sitting for 7 years. After cracking it open i found 3 cylinders will solidly stuck compression rings, so, I'm glad I did pull it apart. This is my primary driver and trailer puller so I'm doing a good rebuild on it. Using the turbo off my other engine... should be good & solid.
I really appreciate all the replies. Thanks a bunch - I feel much better about running them now.
N/A engines actually tend to have more issues with EGT's because they don't have a varying air charge cooling things down, your limited to the amount of air the engine can ingest. If the fuel was ever turned up at all, even a little, it would be vary easy for the EGT's to get out of control on a N/A engine.
N/A engines actually tend to have more issues with EGT's because they don't have a varying air charge cooling things down, your limited to the amount of air the engine can ingest. If the fuel was ever turned up at all, even a little, it would be vary easy for the EGT's to get out of control on a N/A engine.
Not trying to hijack the thread but I read everything here to learn as much as possible. Does that mean if my 89 and 88 are totally stock I should turn the fuel up at least a little Jason? I'm new to idi's and diesel's in general so I'm trying to learn all the idiosyncrasy's of these motors. The 89 is at 130K miles and the 88 is at 60K miles.
Not trying to hijack the thread but I read everything here to learn as much as possible. Does that mean if my 89 and 88 are totally stock I should turn the fuel up at least a little Jason? I'm new to idi's and diesel's in general so I'm trying to learn all the idiosyncrasy's of these motors. The 89 is at 130K miles and the 88 is at 60K miles.
What he's saying is that you need a EGT gauge and to watch your EGTs if you turn up the fuel. You can get more power if you do, slightly... until you run out of air to burn. Beyond that, you just get higher EGTs with no added power.
What you really want to do is throw a turbo kit on them, then turn up the fuel. That'll give you plenty of extra power.
Erosion at the edge of the piston crown is caused by oil getting past the rings and detonating on the compression stroke.
Install a new set of molly rings and reuse the pistons. Yours actually don't look too bad.
Some of the late 6.9 and early 7.3 engines were built with Sealed Power chrome faced top rings produced in the manufacturing process (prior to plating) such that they had a relatively round edge at the top corner of the ring, which hurt oil control.
Later Molly rings are produced with a process that yields a sharp edge.
Exhaust gas temperatures have nothing to do with this problem.
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