ok so the gm847 cam is in and it looks like i will need about 1/4" longer pushrods than the stock size. i have the comp cams measuring tool n i will get a new measurment tomorrow but does this sound about right? prev owner had the heads milled (not sure how much, said 11.1 comp) i have comp mag 1.6rr's and comp 918 springs on stock heads.

 

1/4" longer??

ah that is a big jump...typically with milled heads a shorter one is needed. use PR check tool.

7.200" is stock. test first by removing RR and mark end of valve tip with Sharpie. Install RR and rotate engine by hand 2 turns. Remove RR and see where witness mark is. If dead nuts center you are good. If closer to intake side a longer PR and if closere to exhaust manifold side a shorter one.

set PR tool +/- .050 in the direction you need, re-check and if good order that PR or step another .050 in the direction you were headed.

PR come in .050" incriments typically. You can order specific custom PR but I doubt you are building a $50k race motor. Basically if you measured 7.039 just buy a 7.050

setting the PR check tool to a specific incriment, IMHO, is a quick way. Mine would up 7.100" on my build.....YMMV

 

Make sure if it's a Hydo roller lifter that the lifter is pumped up and the top hat is at the top when messuring. You want to prime the oil system really good to where you get oil out of the lifter hat to make sure it's at the top. 1/4 is way to much. If the heads were milled you would be going down in size a tad not up.

 

.250" is a huge increase and shaved heads should make them shorter, not longer.
Most people end up between 7.100 and 7.200.

Maybe you have long valvestems?

 

7.150's for me with shaved heads.

 

I am running 7.1" with shaved heads and thin head gasket. 1/4" longer I think someone measured it incorrectly.http://www.biggrizzly.com/Lloyd_words.html

 

i've got a nice set of 7.300" for sale!

 

Measure and get back with us