OK i am using a set of protopline BBC aluminium heads. Isky solid roller cam, lifters and rockers. heres the thing, pro topline lit. says i will need an 9.5 ex and an 8.5 int. pushrod. well i measured and i got 9.74 ex. and 8.52 int. so int ake is on but ex is of about 1/4 inch. also the exhaust rocker moves over maybe 50% of the valve stem in its whole throw but the intake covers about 90%. so i am a little worried i have done something wrong here. any thoughts?

 

If I understand correctly that the literature calls for two sizes of pushrods for the intake and exhaust. A 8.50" for the intake and a 9.50" for the exhaust. You did your measurements and you came up with two sizes, one way off and one that is .02" off. You installed the 9.50" and the 8.50" called for in the literature and now the geometry is out?
First, I would verify the pushrod sizes are correct (measure them) and are installed in the proper intake and exhaust locations. If this is all correct, next I would reverify the measurements you have taken. If this is still 9.74" and 8.52", I would have to say you would have to purchase new pushrods for the exhaust and some shims for the intake side. As you know pushrods are usually sold in increments of .25", so it sounds like a 9.75" rod for the exhaust is in order. Good luck and please keep me informed of what is going on.
Other items to look for that can spoil your geometry.
1. Have the heads been milled?
2. Are you using the correct gasket thickness?
3. Has your cam been degreed? Does it match the specifications?

 

Pushrod lengths CANNOT be ordered by the catalog applications and are actually the last "measured" items in the equation, for the following
reasons: there are too many "vendor-variables" involved. Simply put, if you have Std. length valves you'll have a certain length, if you have +.100" longs you'll have another length, and if you have +.250" longs, still another. The final lengths have to be determined at the pre-assembly stage. I have 3 BB's on stands today (retro-rollers), ALL have their own separate pushrod lengths. One has 8.750"/7.900", the second has 8.900"/8.000", and the third has 8.500"/7.550". As I said, it has
to do with vendors tolerances, valve lengths, milling (both head & block), cam "base-circles" and rocker arm choices. You will find if you build (custom) units on a daily basis that valve springs become another entire issue. None of the cam grinders numbers (recommendations) ever really work, again, too many variables. Thanks, Gary in N.Y.
P.S. When you start changing the original dimensions, all the related ones change respectively. Technically speaking, if you mill a deck, mill a head, "sink" a valve, change a gasket size, etc., you will ultimately affect the pushrod dimension. It's a very "over-looked" item that most people take for granted. This is THE major reason we order no parts whatsoever that are assembled, especially cylinder heads. We only order blanks. Due to the relatively "short" pushrods in the BB retro's, we've recently built some with 5/16" diameter pushrods to try to get the reciprocating weights lower in order to raise the "end" RPM limit we're seeing. The only "drawback" at this time is the fact no one makes
after-market 5/16" guide plates. We've spoken to Comp about this also.
We do have to use the more expensive "Hi-Tech" ones for strength however, running some 380# open pressure. We cannot use the less expensive ones here.

 

Sounds like a word from the wise panchop.

 

yea i can dig it. i was geting those lenghts with my checking rods. anyhow i bought that little blue tool (kind of a plastic rocker ) set it up and rechecked. ended up needing a 9.46 and an 8.40 so i ordered a set. thanks for the input.
greg