Sparky

Ok, this should be an easy one!

My GTP Stage II are coming in and I'm told the heads are milled just enough to clean them up (est is .015) Which pushrods should I run - 7.4 or 7.350??? I've already got a B1 cam im my car, if that matters?

Seems like I might be in the "grey" area.

Thanks!

JohnR

iTrader: (1)

I'm running 7.350 pushrods with a Comp 216/220 cam and 26918 springs, everything else is pretty much stock. I still have 1-1/2 turns of lifter preload. So, check your preload with the stock 7.400 pushrods and make sure you are not bottoming out the lifters. As long as your lifters have some preload the different length pushrod won't have any effect on the rocker geometry.

John

LS1derfull

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JohnR:
<strong>I'm running 7.350 pushrods with a Comp 216/220 cam and 26918 springs, everything else is pretty much stock. I still have 1-1/2 turns of lifter preload. So, check your preload with the stock 7.400 pushrods and make sure you are not bottoming out the lifters. As long as your lifters have some preload the different length pushrod won't have any effect on the rocker geometry.

John</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">How much preload do you actually have and why are you running short pushrod with cam that probably has smaller base circle than stock?

JohnR

iTrader: (1)

The short pushrods were supplied by "Internet Racer's Supply" in Houston. They said that they always supply the shorter pushrod because of lifter pump-up at high RPM. Rather than argue the logic of this decision I decided to check it out for myself. Once I saw how much preload that the stock pushrods had I went ahead and tried the short ones. You can easily see the preload when you are screwing in the rocker arm bolts. I used to preload my old '67 400 Pontiac engine's polylocks less than 1/2 turn on a 7/16-20 stud. So 1.5 turns on my LS1 seems like plenty.
I'm guessing that the amount of preload is probably around .050-.060. If I knew what the pitch of the rocker bolt was I could give you a better estimate. I think it goes like this: The lifter preload in inches = the number of turns of the rocker bolt (mine = 1.5) times the screw pitch in inches (?) times 1.588.

Anyway, the car runs fine, no valve tap.
John

LS1derfull

See i agree with them about light preloading of lifter for hi rpm operation. I asked you because i was curious what your thinking was, or if you had shaved heads, Cool Beans! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Sparky

Interesting!

So I may be ok - however - there could be a benefit to running the shorter rods anyway??

Decisions, decsions!!

Thanks

Mark