I'm doing a cam swap and my heads are also being redone. i'm having them milled .020 or so. should i use a stock length 7.2" or a 7.150"? thanx

 

this is not what you are going to want to hear, but there is no way of telling without measuring first. a pushrod length checker is only like $10 and comp cams makes one. put your stockers back in, check to make sure the valve is opening all the way and go from there. it's really the only way to do it.

 

The correct way to judge the pushrod length is watch the travel of the rocker across the end of the valve as it goes from base circle thru full lift and and then back to base circle again.

Use this page from comp cams as your bible.
http://www.compcams.com/Technical/Cu...ML/306-307.asp
Use your stock length rods to see if they meet this requirement. If not you can figure from there which way to go and then order the length checker.

 

I recently had this issue with my setup...running a AFR head with .10" longer valves, a small circle cam and solid roller lifters.

My 7.200" pushrods were way to short. I bought a fancy Lunati pushrod length checker, like $70 or so.

I used a test spring from my cam degree kit and just ran it over, watching the placement of the rr tip in relation to the valve top...but I also run lash caps.

I ended up with 7.850".

 

It MUST be measured.

Rich