X2 on the springs..Also the ls6 cam has a smaller base circle than a standard ls1/4.8 cam..thats what the extra .025 length (over 7.4) on the pr's was for..So they are pushing on the lifters a bit more

 

Better to have extra preload as to not enough? Just not lookin to damage the stock lifters.

 

Higher seat pressure coupled with the more aggressive ramp of the cam is going to make the valve train a little louder as you are going to hear the valve smack the seat regardless of preload. A consistent sewing machine sound is good, lots of clicking, clacking and tapping is not. Not enough preload, you are going to have a sloppy valve train (i.e. noisy) at low rpm. Too much preload, the valves may not completely close at high rpm due to the lifter pumping up.
Without knowing the base circles the LS6 and TU1, I cannot say if you have more/less preload with the same pushrods but I would wager that the TU1 has a smaller base circle thus reducing your lifter preload with the same length pushrod.

 

Im running 7.4 PR with my TU1, LS7 lifters and Dual springs. It does have some sewing machine noise but thats normal with aftermarket valvetrain components.

 

Awesome info guys, thanks. The Ls7 lifters are a different length then stock correct?

Trans is on the dyno today so that's good news, maybe next week she'll be on the streets again!

 

Straight cut gears are fun! They make cool noises... Hahaha

 

Yes the LS7 lifters are different length. I believe they are taller and need 7.35 pushrods on a stock setup but don't quote me. I would buy a pushrod length checker to check your preload regardless. I did quite a bit of reading on preload because I just put a set in myself, best consensus I could come up with was between .060- .09x. Theres a ton of conflicting information out there on these. You should pick up a set of 799's or 243's if your pulling the heads.

 

Only my first gear is cool sounding

 

Results... or vids.... Please....

 

Definitley in for results. I always look forward to the Foose threads.