Thread: Tight Wrist Pins

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Recently gutted my 355 to inspect its innards after finding fine metal in oil. The main bearings look like they had a bunch of trash run through them and are shot - which explains the fine metal in the oil. When I popped out the pistons and rods, I noticed that the wrist pins were tight on all but one. Any ideas?

One guess is bent wrist pins. Some grades of steel (or a thin wall pin) that they are made of can bend with cylinder pressures and RPM. Another possibility is oil starvation to the pin.

lack of oil would be my guess this can be from many things they could have been to tight from the get go or were dry when it was assembled and started to gull then you get black death on the pin bores if a race engine or getting beat on cold you want to add some more sizes to the pin bore lack of oil can be to the way the pin gets it oil to .so when i know it is getting the $IHT BEAT OUT OF IT add clearances to them and other placses to

Tight wrist pins is usually due to piston distortion, not bent pins. I've picked wrist pins up off the pavement after they came out through several layers of iron and they weren't bent!

Originally Posted by R Pope

Tight wrist pins is usually due to piston distortion, not bent pins. I've picked wrist pins up off the pavement after they came out through several layers of iron and they weren't bent!

and i know the guy that has used them flight proven . they are ok

Same here Pat and Pope...... I'm throwing possibilties out for the guy. I have had the very best pins bend on me under dirt track and straight line racing. Gotta give every scenario, that's why they come here for some kind of answers.

P.S. Bores were square, pistons were reused in the next build with no further problems and so on....Anything is a probability. I am with you on oil starvation though Pat. Something went wrong in this project, so I give what I can.

my friend had a 427 that came apart in a big way cut the block in 1/2 had one rod and piston hanging on the wall all bent to hell .one day no rod bolts gone?? next day piston pin ? gone ??? next day just a bent to hell TRW piston hanging on a nail?

Brother if the parts inside these things could talk.....wait a minute...we'ed be out anything too do with our day...

pins can whip. they do . like you said nitrowarrior. but hard to say if he came close to that hp sounds like junk / metal = lack of oil or there is X to ????? had to say what that is??????????

Thanks for all of the input. I'm leaning toward the oil starvation theory. I was able to get them to loosen up after soaking them with penetrating oil. I'm going to get them taken apart to see what else I can learn.