DietCoke

iTrader: (18)

So TSP sent me the 7.8-> 8.8" pushrod checker with my new engine saying it would be the one I needed, because surely I would need longer then 7.8" pushrods. (Instead of the 6.8 ---> 7.8)

So, mocked everything up, and something is way off. No way i'm already at zero lash. Something's off. Stock LS7 rods are 7.8, stock ls3 7.4

My setup
LS3 bottom end.
TSP Small Bore LS7 style heads for LS3 with thick deck (3/4).
LS3 style cam.
YT6670 ultralight 1.8 LS7 roller rockers

Now, correct me if i'm wrong, but the decks/lifter location are identical between LS3/LS7. So given the same base circle cam and SAME HEADS, they would use the same pushrod, right? Which brings me to the next dilemma. I'm assuming the LS7 uses longer pushrods stock because it uses A: the smaller base circle cam and B: has higher p/r pedestals.

So back to my dilemma. My napkin math tells me that I need a SHORTER then 7.8 pushrod, because this engine wont take LS7 length pushrods. I'm assuming it needs LS3 length rods + difference in deck thickness - difference in head gaskets from stock ls3 + whatever the difference from stock rockers to these rockers are. It's hard to say without knowing why ls7 engine need longer pushrods to begin with (chime in, anyone?)

This leaves me with 7.4 + (.750 deck - .4375 deck = .3125) = 7.7125 - head gasket difference (.051 stock - .040 cometics = .011) = 7.7015 minus machining done to head face (asssuming ~.030 for 58cc chamber) = 7.6715, add .050 for preload on the lifter and it *should* need a roughly 7.7215 pushrod. Not anything larger then 7.8

Right? I'm going to try to borrow a shorter checker and try again.

DietCoke

iTrader: (18)

Also, 3/8 vs 5/16 pushrods?

Jason 98 TA

iTrader: (4)

Remember those are ls7 heads just tweaked to fit a smaller bore. They will setup just like a ls7 head. You'll need the ls7 length range pushrods for it. Keep in mind your lifter and rocker setup has changed drastically from stock ls7 so it's important to measure with the long checker and set it up. With a gm lifter and stock rocker you'd be very close to stock, but I'm not sure with that rocker as I've never seen it run.

built408

iTrader: (10)

Definitely 3/8's

DietCoke

iTrader: (18)

It's a GM lifter. The rockers havent change overall length on similar installs. Its just going to end up shorter then 7.8, no big deal. I'll get a shorter length checker.