push rod question

[asloan5]

I have a 109 block with cometic mls gaskets comp hyd roller cam, 885 lifters t&d 1.65 shaft mnt rockers( adjusted in the middle so oil holes line up with opening in rocker) on champion ported irons (shaved 10 thousands). I'm measuring pushrod length at 8.375 with zero lash. Does this size sound correct or possible.
The reason I'm asking on ftss website that combo is calling for 8.225 pushrod length.

 

[gossamer]

Well, Comp Cams recommends the part number 7966-12 which is 8.200" in length. I can't imagine the 1.65 rockers would require that much more length. That does sound a little long to me. I assume you're using a push rod length checker to determine the proper length. Is the thickness of the head gaskets comparable to the stock gaskets? How much was taken off the block if any? A lot of small differences will add up.

 

[turbofabricator]

All being stock, adding T&D rockers requires a .140" shorter pushrod. I use to use chevy lifters on flat tappet cams when converting to T&D rockers. That way I could save the customer a few bucks for pushrods. (I usually was replacing cams when adding T&D's.)

 

[Just a Six??]

I believe those lifters run at almost no preload like 3 thous or something like that? IF your using the proper tool to measure & the geometry is correct then who cares what the number is as long as you did it right with heads torqued down etc. Double & triple check & go for it!

 

[Blazer406]

FWIW... I ended up with 8.350" pushrods. I have a 109.... decked until piston is .010 in the hole... heads skin cut for flatness and finish for Cometic gaskets.... factory hyd roller conversion using lifters from a 3400 V6......and T&D 1.65 rockers....

HTH

 

[ek02]

The best way to determine push rod length is to get an adjustable push rod like the one Full Throttle or Comp Cams sells. Mock up the valve train, but take a majic marker or sharpie and blacken the valve stem. install the rockers and adjust the pushrod to zero lash. You will need a solid lifter, of course, or you can make a solid lifter out of an old hydraulic lifter. Just make the cup length about .030 shorter than a hydraulic. Turn the engine over by hand a turn or 2. The center of the valve stem should be shiney where the roller rubs it. Shorten or lengthen the push rod and readjust the rocker until the mark is dead center on the stem. Then measure the push rod length, and that will be that. It is way more accurate that eyeballing it.