what pushrods???
 

im running a gm847 with 1.6 pro mags ls7 lifters and im just curious if the stock size is ok thx???

I went with 7.3 's on my 355. I am running a XFI280 Comp Cam and LS7 lifters. That's what my p/r length finder said I needed.

Change them out...You really need to buy the measuring tool from Summit so you ensure the correct size. Or search for one on Ebay.

Grab the Comp Cams 7702-1 tool and measure for the correct pushrod length and when you get that pick up some Trick Flow's in that size and you will be good to go.

How do i check for the correct length with the tool do they come with instructions????

http://store.summitracing.com/partde...0&autoview=sku

Is that what you guys are talking about?

I'm going a cam swap, so can't I just measure the ones I take out? Or will a different cam require a different pushrod length?

^^^ that tool will work. If you click on the link in above then click on "instructions" link it describes how to check PR length

A simpler way without the additional tools indicated is:

bring cyl #1 to TDC, remove RR, use stock PR as test PR, mark valve tip with sharpie, put RR back on and lash 1/4 turn, rotate engine by hand 2 turns, remove RR, look at witness mark, if it is DEAD center your PR length is fine. If not than you need to adjust PR check tool +/- in .050 incriments until witness mark is dead center by repeating check process.

cam lift, RR ratio, lifters, head gasket thickness, head and block milling all effect PR length. stock is 7.2"

If your witness mark is closer to intake than a longer PR is needed. If it is closer to exhaust manifold a shorter one is needed.

every set up is different, mine turned out to be 7.100". Went with Trick Flo .80 wall thick PR's