i found a bent pushrod?

[13lazer]

my 1985 suburban C-20 with 350 crate motor bent a pushrod last thursday. i was pushing it pretty hard on the last 5 miles of my daily 50 mile commute. when i got to the end of the freeway the engine was running very rough. i pulled of the valve covers and found the bent pushrod on the exhaust side of the #5 cylinder. i thought my problem was solved, but it still runs rough. the lifter with the replaced pushrod is still pumping oil, but it bottoms out in less than a 1/8th turn. i am kind of stuck now, i don't know what my next move should be? i think i should pull the intake manifold and change all of the lifters, pushrods, and rocker arms. i am hoping there is something else i can try before i tear into the top of my motor. what do you guys think?

[heavychevy79]

Bottoms out?
Is the pushrod guide worn? You might need a self alining rocker from a 87 up engine if it is.
Double check that the pushrod is centered in the lifter.

[13lazer]

what are the symptoms of a worn out lifter? is it possible that i bent more than one pushrod and i can't obviously see it?

[heavychevy79]

You will see it, the rocker will be twisted.
Pushrods don't just bend on their own, the rocker will have slipped off of the
valve because of a worn push rod guide in the head.
If you have a bad lifter you have a bad cam as well, but it's prolly just the the
guides, and the rocker may have cut into the rocker stud too.

[13lazer]

what do you mean pushrod guide? there is just a hole in the head where the pushrod goes through. is it under the intake manifold? i have some experience with small block chevys. are you saying i should change the rocker and the pushrod at the same time. i think im going to invest in a compression tester.

[heavychevy79]

Originally Posted by 13lazer

what do you mean pushrod guide? there is just a hole in the head where the pushrod goes through. is it under the intake manifold? i have some experience with small block chevys. are you saying i should change the rocker and the pushrod at the same time. i think im going to invest in a compression tester.

Yes it's the hole in the head that can get worn and will let the rod shift to the side. The new style rockers hold their place without any help from the
"holes in the heads" and you prolly only need one right now, but other guides may be getting worn. Valves and compression are not affected by this problem.

[billnorman]

Check the height of the valve stems. All of the exhausts should be the same length above the head. Also, measure the pushrod of another exhaust, they may be custom made because it's a remanufactured motor, with head shaving, or such. Sounds a little like a bent valve stem. Usually a stuck closed exhaust will cause an intake backfire with a carbureted engine. Remember, the small block has been around for 54 years, and there have been many iterations of pushrods. You may have the wrong length. Option # 100 is the stud may be crossthreaded below a certain number of threads, or short. If it's oiling, it's probably centered in the lifter. HMMM the lifter.......maybe it pumped up, and broke the clip, stuck at full extension and won't go down......caused the whole problem. Check your oil for Viagra.

[13lazer]

i had the motor revving pretty high right before it started running rough. im thinking i had my valves floating. i just pulled out the new pushrod i had installed and it was bent again. this time i changed the rocker and pushrod and it seems a little better. the motor is a stock gm crate longblock we got from the factory. it has around 30000 miles on it and it is very clean on the inside. before this happened it purred, now it is rough at the tailpipe. i think i might have bent more than 1 pushrod. im going to use a piece of rubber hose as a stethoscope to try to find another noisy valve.

[heavychevy79]

I had more than one worn pushrod guide in my "Heco en Mexico" 993 heads
(GM Goodwrench) but they were fine after I put the new style rockers.
I don't remember having a bent pushrod, but the rockers were cutting into the
rocker stud, and one got cut off!

The engine I just put in my buddy's 83 had a bent pushrod, caused by a worn pr guide, I fixed it with a new style rocker and it has been running smooth.