jebcamaro

iTrader: (28)

I am working on getting pushrod length for my 416 LS3. It's a LS3 block stroked to 416 cubic inches with Mast Motorsports cylinder heads. Mast spec'd it saying the motor would run 8.15" pushrods, but I don't know how they could arrive to that generic statement.

I may have gotten ahead of myself here. The machine shop built my short block and I installed the lifters and cylinder heads. The camshaft is a fairly mild cam for this size engine.

With the LS7 lifters, Fel Pro MLS .042 head gaskets and ARP head bolts all installed, I 'then' checked for pushrod length. The Mast heads are taller than stock heads, so the pushrods will be a bit longer than usual. I used a CompCams 7703 adjustable pushrod which is 7.8" in its shortest length. With the adjustable pushrod sitting on the base of the camshaft, I got 4.5 turns to get zero lash of the rocker arm sitting on the valve. With .050" per full turn and then adding .050" to allow for lifter preload, that equates to 8.075". I don't feel the lifters loading in this calculation, but don't know if I can use this as an accurate measurement to obtain pushrod proper pushrod length. Do I need to disassemble a cylinder head from the block and install a solid lifter or modified stock lifter? If I do, can I still use the head gasket or will I have to purchase a new one? Also, 8.075" pushrod doesn't exist, so what size would I have to get?

G Atsma

Stock is around 7.4". Mast heads are .75" taller, which then adds up to 8.5". So the number would be right if nothing else changed from stock as far as pushrod length goes

jebcamaro

iTrader: (28)

Thanks for that observation. I don't know why I didn't think of the stock pushrod plus the extra heighth of the Mast heads. Only difference is the machinest zero decked the block at 9.035 from the stock height of 9.040 and I'm using a head gasket thickness of .041

G Atsma

Yeah, what I said, THEN you take into account milling and gasket thicknesses, but I think you know about all that....

garygnu

measure pushrod length for every valve .what rocker arms you using ?check the rocker contact pattern on the valve stems

ColeGTO

iTrader: (3)

LS7 lifters have about .210" of pushrod cup travel if memory serves me correctly.

There's quite a bit of "preload range" that you can run in. Some say to run only .050" preload, others say to run more. Some say more preload will make the lifters quieter, some say less is quieter, Some say more preload makes more power and a more stable valvetrain, others disagree.

So basically, each engine/combo may want a little different length pushrod and they only way to know for sure is to test all the different lengths you think you want to run. Good luck.