Why are my pushrods getting bent?
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Why are my pushrods getting bent?
After the cylinder heads were rebuilt, the truck was running great until I raced a chebby and I noticed two pushrods were bent. The motor is a 351M bored .030, .490 lift cam and stock heads. We noticed the motor was running lean to the point where the headers would get red hot which means it needed more timing right? Why were the pushrods bent? Thanks.
Senior User
Joined: Jun 2000
Posts: 175
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From: Mesa, AZ
Why are my pushrods getting bent?
coil bind possibly... make sure you have enough clearance in the spring when the valve is fully open... maybe somebody can come up with a number here, I don't know how much you should have off the top of my head.
didn't happen to mill the heads or block, did you?
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"Get Nitrous & ARBs, Keep Pushing Buttons Till You Make It"
didn't happen to mill the heads or block, did you?
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"Get Nitrous & ARBs, Keep Pushing Buttons Till You Make It"
Posting Guru
Joined: Jan 2000
Posts: 1,899
Likes: 1
From: Cullman Alabama
Why are my pushrods getting bent?
Pushrods can bend from Firing early.
The Fierce detonation with the Intake valve nearly shut can slam the valve up, and the weak link there is the Pushrod.
You may have had Backfire up through the Carb, and never gave it a thought. If that's the case, you might want to check the Gasket under the Carb too.
The Fierce detonation with the Intake valve nearly shut can slam the valve up, and the weak link there is the Pushrod.
You may have had Backfire up through the Carb, and never gave it a thought. If that's the case, you might want to check the Gasket under the Carb too.
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Joined: Aug 2001
Posts: 9
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Why are my pushrods getting bent?
After the cylinder heads were rebuilt, the truck was running great until I raced a chebby and I noticed two pushrods were bent. The motor is a 351M bored .030, .490 lift cam and stock heads. We noticed the motor was running lean to the point where the headers would get red hot which means it needed more timing right? Why were the pushrods bent? Thanks.
but my guesses would be:
excessive rpm on a valvetrain designed for something like 5k max.
do it right go to:
Longer than stock valves for .490 cam lift.
Use appropriate springs for longer valves.
( or cut spring pockets deeper then use longer spirngs
nore expensive, but gives better results due to being lighter)
Roller cam with spring pressure of around 200lb
valve seated( no more than 1000lbs open )
,roller tip rockers and heavy duty pushrods,
screw in rocker studs with girdle, ( I prefer rocker shaft
setups.) Then figure out how to keep the bottom end from
breaking...
next guess is coil bind.
.490 lift cam on stock stock valvetrain that was designed for
something like .450 lift.
milled head and/or block deck on stock length pushrods.
xyz cam company specs their cam as compatible with
stock valve train and fail to mention it's for plain valve
retainers and you've got valve rotators installed.
rocker retainer nut tightned way beyond just enough
to put a little preload on the lifter.
higher ratio rockers installed which decreases cam
lift point at which coil bind occures.
high pressure valve springs installed with stock
pushrods.
Increase in cam lift means you're compressing the valve
spring more, this sends the valve open spring pressure
to an insane level for a stock pushrod.
