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Sat Oct 25, 2008 8:01 am

why do you have to cut push rods......cant you just shim rocker as. away from head or use stock adjusters or some combo like ??? i only have a 100 engle cam... nothing huge....why.........im planning to atleast put on solid rocker shafts but have the hole 125 rocker assembly

Sat Oct 25, 2008 9:27 am

dropgates65 wrote: why do you have to cut push rods......cant you just shim rocker as. away from head or use stock adjusters or some combo like ??? i only have a 100 engle cam... nothing huge....why.........im planning to atleast put on solid rocker shafts but have the hole 125 rocker assembly

It all depends on the combo you are using. Sometimes using shims is ok, sometimes you need to cut the push rods. It all depends on the rocker geometry. There is a sticky at the top of the section that might give you a better understanding. I have done it both ways with success. There is no 100% correct answer.

Sat Oct 25, 2008 9:30 am

what do you mean by combo... like engine combo??

Sat Oct 25, 2008 10:18 am

dropgates65 wrote: what do you mean by combo... like engine combo??

Variables that affect the push rod length include heads used(new, rebuilt, flycutt...etc), case used(new, rebuilt, decked .100" etc), brand and size of piston and cylidner set(some barrels vary in length)

Sat Oct 25, 2008 10:38 am

dont forget cam pushrods and rockers as a variable

Sat Oct 25, 2008 9:00 pm

ooooo ....ok.... every thing was new....even the mofoco profiled heads:)...set for 8to1comp....heres list cb performance case.scat volkstroker3 69 .mahle 90.5s.stock size valves in heads.trw valves.fullflow oil pump.100 engle cam.cromaly stock length push rods.stock rods.koblescmit? bearings.35mm solexes from scat.....put in 65 s-cab ...lowered with drop spindles and the normal bug trans 3.88 and 4th.89.....nice cruiser ..just got a 4+4 quad ....600 lbs.....and wanting to squeaze every bit of power out of my engine to hull it around with....i dont hammer it just want to go down the road better......thinking about flipping the tranny gears and putting rgbs back on and my stock spindles back on....make 1ton again....still have all to switch back.. even tires...:)...just considering my options....plus miss my stock hieght s-cab......

Sun Oct 26, 2008 12:27 am

dropgates65 wrote: why do you have to cut push rods......cant you just shim rocker as. away from head

The mounting studs for the rocker arms and the valve stems are NOT parallel to each other. As you raise or lower the rocker arms with shims, it changes the distance between the rocker arm pivots and the tip of the valves.

You typically shim the rocker arms so that the centerline of the adjuster is lined up with the center line of the valve stem with the valve at 1/2 lift.

Sometimes, due to poor machining, the length from the rocker arm pivot point to the center of the adjuster screw is incorrect. You can either offset grind the mounting stud hole in the rocker arm shaft and rocker arm stand, or you can machine down the rocker arm stand, or buy some rockers that were machine correctly.

Using 911 style elephant feet swivel adjusters does not require as much shimming or grinding of the underside of the rocker arm as the ball bearing style adjuster feet.

Once the rocker arm geometry is set, you cut the pushrod length to fit. As mentioned earlier, flycutting the cylinder heads, the length of the rocker arm bosses, cylinder length, cylinder shims and spacers, case machining, swivel adjusters, rocker arm machining, and cam profile can all affect the required length of the pushrods.

Scott Novak