bent push rod...cause

T

traveler

Member
Hi all.
Hoping someone has some imput on this.
We resurrected a 74 sc II... 304. The engine looks clean...under valve covers...good compression...ran great for a few days.

Then we noticed a clanking...pulled the vcovers and wala...a bent push rod.

After removing rocker shaft to pull rod...we noticed one rocker was wearing bad on the shaft...but still moved freely.

All the rest seemed fine...even the rocker that had the bad push rod...it was better than its neighbor which was scarred metal to metal.

So I guess we will find a new rocker shaft and rockers..these are non adjustable rockers..first I've ever seen.

But my question is....what could have caused the bend...im mean its really bent bad...

All I can think is at some point there was too little oil....the rocker got stiff...and started to bend the rod...and it eventually got so bent it started to clang around
surprizingly ..it was still functioning...just bent all to s***.

Any advice before we put her back together and bend another push rod?
Thanks!
John
 
That engine has low/non-existant oil flow to the rocker shaft spit hole on the rocker/pushrod that has failed. Not an uncommon occurrence at all as you see this same thing time and again in other threads in this sub-forum:

http://www.forums.IHPartsAmerica.com/gas-engine-tech/5199-broken-rocker.html

And:

http://www.forums.IHPartsAmerica.com/gas-engine-tech/5210-345-v8-valvetrain-noise.html

Are examples.

If the rocker system is the "welded" design, then it's common for the rocker to seize to the shaft when it's not being lubricated. That in turn causes the pushrod to bend. Same if a valve sticks due to either non-lubrication or stem varnishing.

If the rocker system is a boat-design, then those have so much slop in 'em they won't seize to the shaft, just wear the hell out of the shaft and rocker wear points to render it unusable. Then the valve sticks due to lack of lubrication for the stem/guide interface.

All rockers shafts and the oil feed rocker stand must be sterile internally in order to be able to supply adequate oil volume to each rocker/valve/pushrod interface in a "timed" manner.

A complete analysis of this situation is posted in this sticky at the top of this sub-forum:

http://www.forums.IHPartsAmerica.co...I-4-sv-engine-non-oiling-rocker-assembly.html
 
I am so grateful for you....gosh.
Do you know how dependent I have become on your brain???

I read the whole thing..every word. Now I know what I'm doing!
Thank you so much!!
 
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