So, I�m having a bit of a delema. I built a stroked ls6. Here are the quick specs.
Callie�s compstar forged stroker kit, h beam rods, Manley pistons with 6cc dish 3.905 dia.
deck plained, prc heads milled (~62cc), using .040 Cometic Head gaskets. When the machine shop did the head milling, they were supposed to leave the Pistons .080 down, but ended up with the odd bank .0040 up and the even bank .0085 up above deck. I ordered an .045 Cometic head gasket to equal them out at around .0040 up. With my gaskets I should wind up with an .036 quench height. I am running a comp cam with 614 int, 621 exh, duration at .050 is 227 and 235, with 113 lsa. Using ls7 lifters. With all that said, I am trying to figure out pushrod length. I measured with comp�s tool, but have come to a roadblock with lifter preload. I did tons of internet searches and ther seems to be 0 consensus. Looking to learn from your mistakes, lol! What should my preload be?

 

I googled LS7 lifter preload, and came up with .020-.050. There is leeway with these lifters. Split the diff and use .035. This is a number I have seen used a lot with these.

 

ls7 lifter has .180 travel, ive always seen as low as .050 and as high as .100 to be accetable for these extremely forgiving lifters

 

Not sure I follow, the pistons are out of the hole 0.040" on one bank and 0.085" on the other? Not sure how that happens through head milling. I am confused so hard to determine what needs to be done.

 

If all that was machined was the heads,, that wouldn't have affected this..

Is the block line bored off center?
Or is it decked funny?
I wouldn't be able to do it,, I'd have to take the block to someone and have the crank/cam/deck heights figured out..

 

The odd bank was decked approximately .0045 more than the even bank by the machone shop. I assume by accident.

 

I dont get why the difference in numbers. I have seen people say .08 and up to .100, and others say .08 is too high and they get lifter noise. Others say .050 or less, but then people say that can cause inadequate valve lift. Most things are cut and dry. This is more of a preference thing then?

 

FYI, i got 9.25 turns on the measuring tool. So 9.125x .05= 0.45625 +6.8=7.25625. Plus whatever preload. I was leaning toward .050. So that would make it 7.30625, or 7.30. Is there a more definative way to decide a more exact target preload? Seems like im just hoping for the best here.

 

Wait wait wait, so thats a typo I hope. .085 out of the hole + a .04 head gasket = piston hit head. So .008" and not .08" I hope? I thought Ls7's worked better in the .07 to .08 (or even the .100 as stated above) preload range for a build of this nature. More preload on the lifter simply lessens the amount of oil in it, kinda like a short travel lifter.

 

ooo somehow i missed the decking issue....i used the measuring tool but measured end to end with a caliper not count turns.

from my research, a general rule of thumb with hyd roller lifters that i have read is no more preload than half the lifter total travel.

 

lol, yes typo. Typing fast on my lunch break. Odd side is .004 and even side is .0085

 

I might lean a little more towards .08ish preload which will get you near .09 hot. Some say travel is .180 and some say .220. You just want to be near the middle, best bet would be to measure the travel yourself and go for the middle

 

Same here. Doesn't make any sense at all to me.

As for the lifter preload question, I'm not sure but with what you're describing with the pistons being so far out of the hole and way higher on one side, I'd be far more concerned with that and not just moving past it.

I see a motor lasting about 5 seconds here..

 

It was a typo. See above, I fixed it. The difference from one side to the other is .0045. I just went with a gasket from cosmetic that was .005 thicker. Now its only off about .0005. Way less error tolerance than a factory engine.

 

I concur! Factory stuff is way off and runs forever!!

 

OK, that makes a little more sense. The standard tolerance on a pushrod length is +/- 0.005" so the difference side to side may not matter much. If you have a set of calipers, you could measure the pushrods once you get them and any longer ones set aside for one bank just so you are not doubling up on tolerance stacks. I would also strongly consider larger OD pushrods, it is a good way to stiffen up the valve train and add stability. Don't know too much about the LS7 lifters, but many seem to run in the 0.070" preload area.

 

So if i go with 7.33 rods that will give me a preload of .074. I think that is what i will settle on.

 

Talk to Manton about 11/32" OD pushrods. Many are running in stock head castings.

 

BTR has 7.325 long 11/16" in stock

 

that sounds like the ticket. Cant find 7.33 anywhere. The 11/32 fit in the cups?