KFK

iTrader: (9)

Some brainstorming for you guys.. I have a stock bottom end LS2 with L92 top end and custom cam with +.600 lift. Runs pretty good but the valvetrain has always been a little noisey. Stone cold (40 degrees F) the 7.350pushrods have about 1 turn preload. but if I run coolant temp to about 130 F and recheck the preload is less than a half turn.... Being AL block and heads I understand expantion but am curious if others have run into this? I also have a set of 7.4 I am thinking of popping in..

kballs

iTrader: (1)

Here's a guideline for setting solid lifter cold lash. It usually put you almost right at the hot clearance specs. It gives you an idea of expansion rates, since they'll be the same amount of change regardless of lifter type.

With iron block and iron heads, add .002"
With iron block and aluminum heads, subtract .006".
With both aluminum block and heads, subtract .012"

I've checked this myself and it's damn near exact.

Danny

iTrader: (16)

I would go with the 7.400s. I had 7.350 on my previous LS2/LS3 topend with a cam in the .595" lift and it was noise. Sounded like valves ticking. I put the stock 7.400s back in to check and it was better. I think something a little bigger than 7.410-7.425 would've done the trick.

racer7088

I agree. Lash changes at most that much on a hot aluminum engine.

.010-.0015 max loss on preload or so is about what to compensate for on an all aluminum engine vs cold.

Pumba

The LS block grows approximately 0.012 inches from 70 degrees F to 190 degrees F. The cylinder heads grow approximately 0.005 inches over the same temperature change. That's a total growth of approximately 0.017 inches.

KFK

iTrader: (9)

I appreciate everyones input on this matter. Being a machinist myself I know how much temp effects plain alum stock so I was curious if others had givin it thought.

Faststudy101

I just installed some Lunati/Morel street link bar lifters. They are quieter cold, and I get increased noise once warmed up. I get an intermittent tick once hot, and some raspy lifter noise through the 2500-3000 rpm range, but not as much as my LS7 lifters caused. Torquer V2 cam, lunati dual gold springs, lunati street lifters, ported 243 headed, LS2 with ARP rod and head bolts. Completed the rebuild myself.

I'm around 3/4 rocker bolt turns from zero lash to 22ft/lbs now, which puts me around .036 for a preload number cold. So its dropping to the low .020 hot... The form recommended .045 and most are saying .020-.040. I may try some 7.4 hardened rods next, as those are a hair longer than stock. I have some 7.425" comp pushrods too, but was at around 1.25 turns with those and don't want to go too high. I've considered lighter springs to reduce noise as well.