The Stovebolt Site Forums The Shop Area Engine Shop Bent rod

Got a pretty bad knock in the 228. I'm by no means a mechanic, but was told by a friend that listened to it, probably a bent rod. Does anyone know an honest dependable mechanic here in the Tulsa area, that might take care of the problem on Ole jimmy. Thanks
http://rides.webshots.com/album/569509626jmfVkR

That's a nice looking jimmy you have there. Knocks can be anything from a valve adjusted way to wide to piston slap to bearings. I'm not quite sure how your friend decided it had a bent rod, but doesn't make sense to me. I've been working on GMCs for over 50 years and I don't think I ever came a across a bent rod that caused a knock. I am to far from Tulsa to know any mechanics, but there has to be some old timers around still working. You might pull the valve cover and try sticking something between the rocker and the valve one at a time while its running and see if it makes any difference. The intakes are supposed to be .012 hot and the exhaust .020 hot.

Did he mean , bent push rod? Thats far more likely.

He did say push rod.

It can't be bent very much, or it'll jump out and that cylinder will stop working.

take crenwelge's advice and get yourself a repair manual. the engine is not really that complicated and a push rod can be changed out fairly easy.

How did the knock start? It would take a fairly good hit of water to bend a connecting rod, or a big shot of Nitrous Oxide!

Old engines are very easy to work on, take one step at a time and we can walk you through it.

Pull the valve cover and check around for extra loose rocker arms, even start it up with the cover off and look and listen. If everything looks OK, pull the oil pan off, it needs cleaned out anyway. Check for loose rod bolts or main bolts, or signs of heat or stress.

Give it a try before sending it out. Joe

The 216 in my one ton recently developed a knock.
I thought it was serious, but after further investigation it was indeed a bent pushrod. The truck was recently run on the bad gas that was in the tank before I acquired it, resulting in a few stuck valves and bent pushrods. One rod was bent just enough that it was slapping the side of the block as it spun around.
I replaced 2 bent rods, freed up the valves and added some marvel mystery oil to the crankase and ran some through the carb as well. No problems since.
Not saying that is what your problem is, but it is possible.
Replacing the rods is very easy.

get a pair of insulated pliers and leather gloves.
with the engine running remove the plug wires one at a time and put them back on, don't let your belt buckle rest on the fender, don't ask.
if the knock goes away you have isolated your problem to a rod bearing or wrist pin and which cylinder.
If it dosent go away it is most likley in the valve train.

What ghostrider said.