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bent push rods

 
dale49
I love my Chevy Chevette!
Posts: 16
Joined: 07/13
Posted: 01/05/14 01:22 PM

i have an 89 chevy 350, it keeps bending breaking push rods, cyl, 2,4 and 8. 2and 4 have been changed once, #2 has been changed 4 times, the motor is stock, has elf centering rocker arms and the small holes in the head, trk ran fine yesterday, i went out there this morning and started it and it broke those three push rods, it only does it when its cold and you are starting it, there all intake valves. i have seen the valves stick open then slam shut after the rocker arm goes back down,once it warms up it runs fine, any help would be greatly appreciated thx dale  

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wayne712222
V-6 Camaros rule!
Posts: 90
Joined: 11/13
Posted: 01/05/14 05:14 PM

i have seen carbon build up on the valve stem hold the valve open and prevent it from closing cold..

i have seen too tight valve guide clearances cause the same issue...

thin wall valve guide liners have also slipped out of position..

when i ran a cylinder head department in a small engine rebuilder back in the 90s..

i started using stay lube moly graphite assembly lube on the stems instead of motor oil. i also placed some around the top of the guide where the valve stem stick thru.. this leaves a reservoir of assembly lube under the seals to lubricate the stems in operation.


you will also want to check the sides of your rocker arm studs for signs of rocker arm wear down on below the threaded area. this can happen allowing the rocker arms to pitch over sideways and grab tight onto the rocker arm stud..  

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joe-
I love my Chevy Chevette!
Posts: 13
Joined: 01/13
Posted: 01/09/14 03:06 PM

this reminded me of a thread i read not long ago.   might be some info in there that you might find interesting?  
http://www.thirdgen.org/techboard/tpi/673803-self-aligning-not.html

i'd want to determine why the valves are sticking.  carbon?  bent?  bad valvesprings?   etc.

let us know what you find out.  
joe-

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