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Discussion Starter #1 (Edited)
this is my 3rd engine assembly so you can say major noob for this engine.

i ran ported gt40's with larger chevy valves and cobra 1.72's with stock roller pushrods that were just right with stock head gasket and cam. block was not decked nor the heads.

installing a custom cam now using the exact same parts but now the pushrods are WAY too short. and it may just be me but the lifters seem to sit lower in the block than with the oem cam, again, may just be me.

i have an adjustable pushrod checker but don't know if im doing it right?

my question is, how to accurately measure for new pushrod length so i can order the correct ones.
ive got a short video of the play in the pushrods, these pics were taken with the pedestal mounts torqued to 24#'s and the play in the pushrods. with everything torqued, the pushrods move up and down about 1/8th of an inch and there is no preload what so ever.

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IMG_20201121_115738.jpg
 

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aka: kemicalburns
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i was always taught to tighten them down till they dont move, then a quarter turn out. they should spin but have no other movement.
 
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Discussion Starter #4
351 roller, always been a roller, its like the cam is smaller in diameter. ive got a vid but dont know how to post it
 

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'92 Custom w/ '95 MAF 5.0 M/T, 33's, 4.10 LSD
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I just posted this link in another thread...


"the Comp [35-512-8] cam is probably ground on a stock camshaft blank. So in order to get higher lift on the lobe, the base circle was probably slightly reduced in size. Hence the potential need for new pushrods and shims."
 

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Discussion Starter #6
its a custom grind from cam research and is the only thing that is different or that ive changed. maybe they regrind a stocker? idk......what i do know is the pushrods are way too short now.
 

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Man of endless projects
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I just posted this link in another thread...


"the Comp [35-512-8] cam is probably ground on a stock camshaft blank. So in order to get higher lift on the lobe, the base circle was probably slightly reduced in size. Hence the potential need for new pushrods and shims."
heh you found my old thread. it defiantly taught me the lesson that if you change anything in the valvetrain, you can never assume that the original pushrods are the same length. anything can change the geometry inclueding base circle diameter of the cam, different pushrods, different heads, milling block or heads, machinging valves, even seen some small differences in lifters.

hydrualic lifters want about 1/4 to 1/2 turn of preload on them (many argue which is better i go with 1/2). thats means tighten the bolt till you jsut take out all the slop in the pushrod, then it should take about 1/2 turn and it should meet torque spec of 18-25 ft/lb if you are using stock pedistal rockers arms. the opposite is true to solid lifters that want a gap (valve lash) between valve and pedistal to account for expansion of metals

since pedistal rockers have no way to change geometry like stud mount rockers, dont worry too much about doing the marker on the stem thing. you wont be able to change that anywasy. you jsut need to measure pushrod length with the checker tool to get a length till you are within that range of preload. there is also a shim kit avalible for pedistal rockers in order to fine tune for geometry and pushrod length. id recommend getting it jsut incase. sometimes cant find the exact length you need

i was always taught to tighten them down till they dont move, then a quarter turn out. they should spin but have no other movement.
maybe on a solid lifter. on a hydrulic lifter they need to be turned tighter, not looser
 

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'92 Custom w/ '95 MAF 5.0 M/T, 33's, 4.10 LSD
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heh you found my old thread.
You know what they say, anything worth searching is worth re-searching...

there is also a shim kit avalible for pedistal rockers in order to fine tune for geometry and pushrod length. id recommend getting it jsut incase. sometimes cant find the exact length you need
That wasn't directed at me, but it answers one of my lingering questions. I should go ahead and order a set of shims.
 

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Discussion Starter #9
yeah ive got the tool but never used one,
what im doing is taking all the slop out of the adjuster rod, tightening the 1/4" allen head so that i reach 18-25#'s in about half of a turn once the slack is out????? does this sound right? anything longer than what ive got is better......hey wait a minute, i meant pushrods.
 

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If you're using roller rockers, hydraulic, you snug them until there's slight resistance while spinning the pushrod then go about 1/2 turn additional to slightly preload it. You'll still be able to spin it. Basically zero lash plus half a turn. Too loose and they'll be noisy, too tight you won't get proper lift.

When using a pushrod length checker I always grab a couple solid lifters since they don't collapse and you can get a better measurement.

Mark the top of the valve with sharpie and turn motor a couple revolutions by hand. Wear mark should be as centered as possible on the valve stem. Don't forget lube on the lifter.

Unless I misunderstood the question.

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