stock lifter preload
#4
PT's Slowest Truck
iTrader: (19)
You could try calling the dealership, but I don't think that you'll get a straight answer. Maybe try PM'ing Zippy, he worked for a Chevy dealer for a long time, and is probably your best shot. If you have problems getting in touch with him here, try over at SilveradoSS.com, he's and admin there and on that site pretty much every day...
If you find out, post up your findings...now I'm curious to know myself
If you find out, post up your findings...now I'm curious to know myself
#7
that number is what I "remember" from doing my cam last year.
After squishing the lifter .030" from zero lash, my push rods had to be .070" shorter than stock. I assume my valves are worn that much. Still no bad sounds from the drive train. Pity GM didn't use adjustable rockers.
After squishing the lifter .030" from zero lash, my push rods had to be .070" shorter than stock. I assume my valves are worn that much. Still no bad sounds from the drive train. Pity GM didn't use adjustable rockers.
Trending Topics
#8
Here are the factors that I can come up with for calculating the factory preload with an aftermarket setup...
Assuming the factory PRs are 7.380"
Factory PR preload - Zippy got back to me and said it was .050" - .090"
With that said, I am shooting for .070" preload
Variance in compressed Head Gasket Thickness - I have been told that the stock gaskets are .051" - .053". I installed a .041" gasket, which is a variance of .010" - .012", assuming .011" head gasket change
Lifter height - I installed LS7s which "reportedly" are .050" taller than the 2003 LQ9 lifters.
Given this info, and assuming the valve spring installed height is the same, lets do some math...
.070" preload with 7.380" PRs
change head gasket, preload goes to .081"
change lifters - Preload goes to .131"
Adjust PR length for .070 preload gives a .061" shorter PR.
7.380 minus .061" gets us to a 7.319" PR for .070" preload
7.325" PR gives us .076" preload
7.300" PR (whats installed now) produces .056" preload (on the loose side of acceptable range)
7.350" PR produces .096" preload - too much for my liking.
7.325" is the winner!!! (provided the spring installed height is the same as factory). That is the only variable.
Lesson learned - always get adjustable rocker arms.
Assuming the factory PRs are 7.380"
Factory PR preload - Zippy got back to me and said it was .050" - .090"
With that said, I am shooting for .070" preload
Variance in compressed Head Gasket Thickness - I have been told that the stock gaskets are .051" - .053". I installed a .041" gasket, which is a variance of .010" - .012", assuming .011" head gasket change
Lifter height - I installed LS7s which "reportedly" are .050" taller than the 2003 LQ9 lifters.
Given this info, and assuming the valve spring installed height is the same, lets do some math...
.070" preload with 7.380" PRs
change head gasket, preload goes to .081"
change lifters - Preload goes to .131"
Adjust PR length for .070 preload gives a .061" shorter PR.
7.380 minus .061" gets us to a 7.319" PR for .070" preload
7.325" PR gives us .076" preload
7.300" PR (whats installed now) produces .056" preload (on the loose side of acceptable range)
7.350" PR produces .096" preload - too much for my liking.
7.325" is the winner!!! (provided the spring installed height is the same as factory). That is the only variable.
Lesson learned - always get adjustable rocker arms.
Thread
Thread Starter
Forum
Replies
Last Post
lxcoupe
GM Engine & Exhaust Performance
1
07-30-2015 02:42 PM
Suburban2500
INTERNAL ENGINE MODIFICATIONS
31
07-19-2015 04:50 PM