pushrod length and valve lash adjustment
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pushrod length and valve lash adjustment
i run a set of ported vortec heads and proform roller fulcrum rockers (1.6 to 1), in my last build i was having a hard time setting valve lash correctly, i could only get 1/4 turn on my rockers, after that they were holding my valves open.
i had wondered then if i should have changed my pushrod lenght, but couldn't find any info on this. in my new build i am running the same heads and rockers just adding a larger cam ( i'm selling the old one xtreme energy 262 if anyone wants it let me know), this time the book calls for comp cams(CCA-7812-16) pushrods which are 7.794" long. what is the stock length for the pushrods in an '85?
i have searched summit, jeg's, etc. and there seems to be a range of rods available, from 7.400" and up , all being called "stock". i'm a little confused on this, as usual.
what i need to know is the stock length and if longer or shorter rods would effect my valve adjustment.
thanks Greg
i had wondered then if i should have changed my pushrod lenght, but couldn't find any info on this. in my new build i am running the same heads and rockers just adding a larger cam ( i'm selling the old one xtreme energy 262 if anyone wants it let me know), this time the book calls for comp cams(CCA-7812-16) pushrods which are 7.794" long. what is the stock length for the pushrods in an '85?
i have searched summit, jeg's, etc. and there seems to be a range of rods available, from 7.400" and up , all being called "stock". i'm a little confused on this, as usual.
what i need to know is the stock length and if longer or shorter rods would effect my valve adjustment.
thanks Greg
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From: SE NY
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Indeed Comp Cams lists the 7.794" push rod as stock for the flat tappet cam engines.
The push rod length must be chosen so as to keep the rocker moving symetrically across the valve stem tip. They do not effect valve lash setting.
Before setting lash just set the rockers loosley onto the studs and rotate the crank till both valves are closed. That will give time for the lifter spings to raise the pistons to top of their bore. Then you can set zero lash plus the 1/2-3/4 turn preload.
If you cannot get the polylocks screwed onto the studs at all without applying pressure to the rockers you likely need longer studs.
The push rod length must be chosen so as to keep the rocker moving symetrically across the valve stem tip. They do not effect valve lash setting.
Before setting lash just set the rockers loosley onto the studs and rotate the crank till both valves are closed. That will give time for the lifter spings to raise the pistons to top of their bore. Then you can set zero lash plus the 1/2-3/4 turn preload.
If you cannot get the polylocks screwed onto the studs at all without applying pressure to the rockers you likely need longer studs.
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From: Database Error Indiana
Stock on an 85 is 7.8" (7.794 if you want to be picky) . Make sure the underside of the rocker is not hitting the edge of the valve retainer. The rocker should be riding near the center of the valve tip. Not biased to one edge or the other. The pushrod has to be moving free in its slot, not binding. Easier for me to do than describe.
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From: The Top of Utah
Originally Posted by atotalnincompoop
i could only get 1/4 turn on my rockers, after that they were holding my valves open.
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Keep a close watch on those Proform rockers, too. They are not known for their longevity and the roller tips will begin to disintegrate before long.
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From: eville in
Originally Posted by Corvette Kid NC
Keep a close watch on those Proform rockers, too. They are not known for their longevity and the roller tips will begin to disintegrate before long.
