D2 #3 piston compression height

Of all the hundreds of engines I repaired I never ran in that but guessing it could be a couple things causing it.First maybe an after market piston was put in and wasn,t made up to specs. or if the rod was damaged from a bad bearing then it could have been machined out and resized (and not centered correctly) which we did to lots of them at the dealer.Also the rod bushing wasn,t bored and centered correctly to specs.That,s about all I could guess is the problem.

Of all the hundreds of engines I repaired I never ran in that but guessing it could be a couple things causing it.First maybe an after market piston was put in and wasn,t made up to specs. or if the rod was damaged from a bad bearing then it could have been machined out and resized (and not centered correctly) which we did to lots of them at the dealer.Also the rod bushing wasn,t bored and centered correctly to specs.That,s about all I could guess is the problem.

.100" is a startling variation in piston height to encounter, and if I were you, I'd be greatly concerned, and be pulling all the pistons to determine the cause.
One piston that low is probably barely creating enough compression to fire, and I'm surprised it hasn't been running without a miss.

Cat had 2-piece pistons during the early 1940's, that created a deal of havoc when the piston tops came unscrewed from the lower part of the piston .. and Cat devised a better retention method for the piston tops .. then did away with 2-piece pistons altogether.

I'd have to say that someone fitted an incorrect piston or conrod .. and I'm amazed it wasn't noticed when the engine was last re-assembled.

You sure that the liner is seated home?,if it was going alright before it should go alright when you put it together, I have seen loads of engines with an odd aftermarket piston that would not be the same as the others,if it goes alright no one will see it and I would not worry about it.
AJ

I'm with Oz, I just finished getting the "new" pistons for my D3400. There was a recall on those two piece pistons oh... 50 years ago.

You don't want that top doughnut of the two piece to come off like it did with me.

I would not want to assemble an engine to later have it come apart sending shrapnel throughout. Better to be thorough than sorry.

My $.02 worth

CMD

Maby it would be wise to measure the stroke of all pistons and also the maximum depth of piston stroke from a common datum elevation---if the stroke is all the same for all 4 pistons and #3 bottoms out lower in the bore as much it is lower at the top of the stroke then i would guess it is just a smaller hight piston.

I plan to pull the piston/rod tonight. Will it fit past the crank? I dont want to pull the crank.

I plan to pull the piston/rod tonight. Will it fit past the crank? I dont want to pull the crank.

Bet it's a bent rod.
Bob