Weird marks on pushrods

kole32

kole32

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Oct 7, 2012
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Recently blew a headgasket on my 12 valve and I noticed some strange marks on the pushrods ? I've looked at the head and the block and see nothing it could be hitting. It's on 8 of the pushrods some is worse than others.

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Hard to tell from the pic but looks like where they were welded together.
 
90% sure the marks weren't there when I got them lol. I just can't see anything that they could be running against to cause those marks. You can feel the groove on a few of them.


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what size pushrods? looks like they might be touching a bit where they pass through the head somewhere in the cycle. mine doesn't have much clearance there but I only have 3/8 pushrods.
 
I'm pretty sure they're 7/16 pushrods. That might be it. I put them in a spare block I had and it looks like there's plenty of clearance.


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I'll check it out later today and let you guys know. I've got no clue. Looked like there was plenty of clearance between the head and the pushrods.


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The problem I see with the head rubbing part is there looks like there is a crack dead center of the mark. Alot of pushrods especially performance ones are not 1 piece. They are multiple pieces welded together to strengthen certain parts
 
Last edited:
DISTURBED said:
The problem I see with the head rubbing part is there looks like there is a crack dead center of the mark. Alot of pushrods especially performance ones are not 1 piece. They are multiple pieces welded together to strengthen certain parts
Click to expand...

It is a rub, guessing only rubbing at the higher lift of the cam as the rocker is near the top and is headed towards the head.

Is it a tapered pushrod?

You could also be seeing some pushrod deflection.
 
Is it possible it is a weld joint and has rusted there from moisture. You know like when you pull a valve cover from one that has sat and you see kinda milky oil sludge. If they all look the same it would be strange they wore the exact mark from a cast head.
 
zstroken said:
It is a rub, guessing only rubbing at the higher lift of the cam as the rocker is near the top and is headed towards the head.

Is it a tapered pushrod?

You could also be seeing some pushrod deflection.
Click to expand...



That's what I was wondering ! If it was deflection, but they're a pretty beefy pushrod. I doubt I'm making any more than 700hp. I was running 70psi of boost.
 
Got it figured out. Talked to the machinist and he said with 7/16 pushrods it hits the head. He said factory rods are close clearance when the valve is fully open.


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correct 7/16 rubs the head on 12v, that's one reason i run some 3/8 heavy duty wall, unless we do a tapered 7/16 rod which wont rub, but the cost is a good jump up.
 
I have some 7/16" Mantons in my truck now. Will the rubbing eventually cause them to fail?
 
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