Pushrod length with LS7 lifters
12-02-2013, 09:35 AM
#1
Pushrod length with LS7 lifters I am doing a h/c swap in a few weekends and want get a general idea of what length pushrod I will need with my setup. I will be measuring on the spot, but I only have one chance to do this whole thing so I want to be in the ballpark, order a few different lengths and then after measuring pick one of those. So the closer I can estimate it, the better I will be when ordering.
Setup is comp LSL/LXL cam, 0.040 cometic gaskets, 243 heads shaved 0.030 and new LS7 lifters.
I've heard that LS7 lifters are 0.060 taller or something, so they require a shorter pushrod. Is that the case? In total that means I need a pushrod close to 7.300 after the milling, thinner headgaskets and new lifters?
Setup is comp LSL/LXL cam, 0.040 cometic gaskets, 243 heads shaved 0.030 and new LS7 lifters.
I've heard that LS7 lifters are 0.060 taller or something, so they require a shorter pushrod. Is that the case? In total that means I need a pushrod close to 7.300 after the milling, thinner headgaskets and new lifters?
12-02-2013, 12:02 PM
#3
I get that's the best way to do it, but unfortunately I cannot just tear down the car to measure and then wait 2-3 days for the correct pushrods to come.
I need to be able to pick out the correct pushrods out of the tool box after measuring, and this entails having several different lenghts already purchased and I don't want to buy 20 sets. Need to narrow it down to a few through calculation and then I would measure for the exact one I need. Just trying to figure out this lifter situation.
I need to be able to pick out the correct pushrods out of the tool box after measuring, and this entails having several different lenghts already purchased and I don't want to buy 20 sets. Need to narrow it down to a few through calculation and then I would measure for the exact one I need. Just trying to figure out this lifter situation.
12-03-2013, 07:59 AM
#7
7.375 would be my guess if you don't want to measure. You have a very wide preload window with LS7 lifters, so you could be off by .050" and it'd still technically work. 7.425" would be the length with a smaller base circle cam and stock everything. Milling the heads and running a thinner gasket means you can take that off... 7.425 - .041" = 7.384" length. 7.375 is as close as you're going to get off the shelf.
BTR has them for $94. Best price I've found on standard 5/16" pushrods.
BTR has them for $94. Best price I've found on standard 5/16" pushrods.
Trending Topics
12-03-2013, 08:07 AM
#8
The cam base circle plays a role as well but I too would suggest 7.375" as a starting point. LS7 lifters are the same length as LS1's. I have what you see below and needed 7.425" (measured) with a .051" gasket and unmilled GM casting heads. You lose .011" to the gasket and .030" to the mill. My 228r also had a smaller base circle than a stock ls1 cam.
A 7.375" will net you .009" less preload than I have given same cam base circle and valve stem lengths.
End of the day.....measure twice (or 16 times) buy once. The length checker is <$15 from Summit or Jegs and I'm sure TSP could have the proper rod out to you in a couple days after you measure.
A 7.375" will net you .009" less preload than I have given same cam base circle and valve stem lengths.
End of the day.....measure twice (or 16 times) buy once. The length checker is <$15 from Summit or Jegs and I'm sure TSP could have the proper rod out to you in a couple days after you measure.
12-07-2013, 11:32 AM
#9
I have personally measured LS1 lifters compared to LS7's. The LS7 lifter cup sits .050" higher than the LS1 lifters. I ended up using 7.375 pushrods with GM MLS gaskets and stock 799 heads to achieve a preload of .085" average (was measured with a comp pushrod length checker and dial indicator). In your case, using a .040" gasket (-.011") and heads milled .030" (-.030") I would suggest using a 7.325 - 7.350 length pushrod.
