stock 1991 4.3L bent a pushrod?

have a 1991 c-1500. after switching from 5w-30 to 10w-40 oil it started ticking. i switched it back to 5w-30 oil and it bent a pushrod 1 week later:eek:.
truck has 182,000 miles on it and is stock. i found the pushrod in the lifter valley, after taking the intake off

the bent pushrod happened on cylinder #2 intake valve.

does anybody have any knowledge about why:confused:? (collapsed lifter???etc...)

thanks for your help. Mike

First Guess: Totally unrelated to the oil change.

The knowledge about "why" will come from the disassembly and careful inspection of the rest of the engine.

Second Guess: Flat cam lobe leading to excess lash (ticking) and then enough lash for the pushrod to fall out-of-position and get bent.

thanks, i will see if the lifter on the offending cylinder rises as much as the other lifters! mike

LOL @ "get bent"

thanks, i will see if the lifter on the offending cylinder rises as much as the other lifters! mike
Pointless and inaccurate.

You have the manifold off. Pull the lifters out and inspect the bottoms and the lobes.

well all is back togehter and is quiet. i checked the compression on the #2 cylinder when done and got 165psi! running real quiet!.

so what was the culprit?

Yeah!!! tell us what was the culprit!!!

I would guess the ticking plus possible "valve floating" at high rpm caused the pushrod to come out of the lifter or rocker leading to the "get bent" situation.

the lifter on cylinder # 2 pushrod came apart (exhaust valve). the clip in the top of the lifter was missing and the top plate of the lifter made its way sideways and jammed itself between the #2 intake pushrod and the block bending it. i tested the compression in that cylinder when all was back together and got 165psi, so no valve damage!!!!
i found the top of the #2 exhaust lifter in the intake valley with road rash all over it! their was also road rash on the #2 bent intake pushrod, so the two met before! mike

i found the top of the #2 exhaust lifter in the intake valley with road rash all over it! their was also road rash on the #2 bent intake pushrod, so the two met before! mike



Sounds like they had meeting, and then the push rod got told to get bent on the second date.