luisdavid11

iTrader: (2)

would i need shorter pushrods with .030 milled 317 heads on an lq4 with stock gm head gaskets and a 228/228 .588 .588 110 lsa cam and set of new ls7 lifters ? or will some comp cam hi-tech 7.4 pushrods work fine ?

thanks in advance guys.

01ssreda4

iTrader: (96)

Stock pushrods won't work, they're weak enough as is and can't handle an aftermarket cam. If you meant stock length, well you may be ok. Here's why: Typically stock pushrods are right at 7.40, and aftermarket cams are smaller then stock cams and usually require a slightly longer pushrod, say 7.425. Now if you milled your heads .030 then that puts you right back at the 7.40 range with stock preload levels. I would however double check the measurement with a pushrod checker just to be 100%.

luisdavid11

iTrader: (2)

sorry about that, yes i meant stock length.

luisdavid11

iTrader: (2)

forgot to mention i'll be install new ls7 lifters. been reading about the preload on them is different or something like that.

01ssreda4

iTrader: (96)

Nope, its the same. That's a myth that just won't die.

luisdavid11

iTrader: (2)

ah okay haha gotcha. i'm new to this so i've been doing lots of reading on here and been seeing that a lot

poltergeist 02

iTrader: (65)

This is wrong. I have personally measured LS7's and stockers with a dial indicator and ther is a .050" difference. The LS7 lifters are .050" taller.

Havoc40

I guess I have to pull the pictures out again. Here's a collection of parts dating from early 90's to present. All "LS7" style lifters, otherwise known as OEM replacement lifters. Couldn't find the early LS1 style lifter for the group, but it's the same. The measurement pictures are of a brand new LS7. I could post the pictures of all the measurements...but I hope you'll take my word for it.

Zero'd with 2.500 blocks

Extended over .3125 ball

Collapsed over .3125 ball

All of them



Measurements
1st set of pictures: 2.6511" extended; 2.4478" collapsed. Total travel of .2033"

Bottom pic from left to right...(the 2 missing measurements weren't listed because the piston wouldn't move from sitting for years)

Sample part #1 (part 1): 2.6588 extended length; 2.4565 collapsed length. Total travel of .2024"
LS7 sample #2 (part 4): 2.6562" extended length; 2.4486 collapsed length. Total travel of .2076"
Sample part #2 (part 5): 2.6491 extended length; 2.4565 collapsed length. Total travel of .1926"

luisdavid11

iTrader: (2)

wow good info, Havoc. So what you're saying is that by milling the heads .030, I should be fine with the 7.4 correct? If i had stock heads, i'd need bigger rods, 7.425 due to the ls7 lifters, but since I'm milling, the 7.4 should be fine?

Havoc40

Like 01ssreda4 mentioned, due to cam base circle variations and a multitude of other variables, when something is changed in the valve train you want to measure. That way you won't have to start another thread about noisy or broken components in the valve train. You might be just fine with 7.400, but is it worth the risk not to measure? I know I can't sleep at night with things like this rolling through my head. Just something to think about...

luisdavid11

iTrader: (2)

yeah i got you. rather spend a few bucks in a $20 length checker than live with the fact that i messed up an engine due to a $20 tool lol. nonetheless, thanks for the input guys. i appreciate it.

poltergeist 02

iTrader: (65)

No, buy a pushrod length checker and see for your self that your 7.4's are too long for your set up. You will most likely need 7.35 - 7.375 pr's but you should measure to be 100% sure.

luisdavid11

iTrader: (2)

will do. thanks man.

new2dgame

pick up my 241 heads from machine shop...so this is my ??? he milled the heads 40 thousandths is that too much i know i have check pushrod length but is thier anything else i need to check

03Sssnake

iTrader: (20)

You might have trouble getting the intake manifold to seal up with .040 off, but opinion varies on this. Are you using GM MLS gaskets, or a thinner cometic gasket? You should still measure for sure though. I ended up needing 7.375 length PRs with my milled 243s and F13 cam (new LS7 lifters and lifter trays)..

01ssreda4

iTrader: (96)

^^No he won't. Intake will seal fine.

tj613tjtj

did you ever find out what push rods you needed?

cmysix

iTrader: (2)

It's not a myth, pre LS7 lifters the preload that GM put out was like .80, GM says with LS7 lifters .090 and I not sure but BTR or Tick says they like to go .100, after all the range is .200