Heat Expansion and lifter pre-load....
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Teching In
Joined: Jan 2005
Posts: 28
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From: Doylestown,PA
Heat Expansion and lifter pre-load.... Just wondering if anyone knows approx how much and LS motor actually would expand with heat. Checking pre-load of lifters. And checked while hot and with seeing all these varying specs was just wondering. I have seen that some have said about .010 difference from hot to cold. My pre-load right now with a dial indicator is .052 Which dependent on whos specs GM's or other manufactuers I would be good or I would be to loose. Since some say GM is .090 to .110. so on a hot engine that would be .080 to .100. And on other specs that would be .020 to .050. So that is why I 'm trying to see. I think it may be the cause for my noise. Since I'm looser then GM specs. Any help is greatly appreciated. Thanks.
I was running less cold pre-load than you (about 1 turn, which equals .03x") and I had no noise. This works out to a warm preload around .020" (.012" block growth). From Tony's post below, it looks like stock pre-load is in the .060" range.
As a comparison, Comp R lifters recommend .002-.004" pre-load which is really only achievable with adjustable rockers or through custom pushrods on a stock setup. This info doesn't seem to be correct in real life though-
Here is some valuable info from Tony Mamo (post 38 in this thread: https://ls1tech.com/forums/showthrea...ifter+pre+load)
"As far as preload, I have seen close to 2 turns with a stock GM lifter set-up. I noticed that when I took my engine apart. I would say anywhere from 1-1.5 turns would be fine. By the way, I did some dyno testing with my "R" lifters and from .010 preload (valvetrain making a racket) to .055-.060 preload (lifters MUCH quieter), I saw ZERO difference in power anywhere in the curve. Guess where I run my Comp "R"'s ?? (hint: think "quiet")."
To sum things up:
It is important to keep the following factors in mind when dealing with valvetrain geometry- base circle differences, lash (or lack of it), lifter pre-load, block growth (cold vs. hot measurements), rocker wipe on valve (changes desired pushrod length due to shimming/milling rocker pedestal to achieve correct wipe)
For my part- I just suffered a needle bearing failure (with resultant engine failure) in a stock lifter so I'm thinking of getting Comp Rs and running them with stock with somewhere around .020-.040" hot pre-load as Tony suggests.
Thanks
Ben
As a comparison, Comp R lifters recommend .002-.004" pre-load which is really only achievable with adjustable rockers or through custom pushrods on a stock setup. This info doesn't seem to be correct in real life though-
Here is some valuable info from Tony Mamo (post 38 in this thread: https://ls1tech.com/forums/showthrea...ifter+pre+load)
"As far as preload, I have seen close to 2 turns with a stock GM lifter set-up. I noticed that when I took my engine apart. I would say anywhere from 1-1.5 turns would be fine. By the way, I did some dyno testing with my "R" lifters and from .010 preload (valvetrain making a racket) to .055-.060 preload (lifters MUCH quieter), I saw ZERO difference in power anywhere in the curve. Guess where I run my Comp "R"'s ?? (hint: think "quiet")."
To sum things up:
It is important to keep the following factors in mind when dealing with valvetrain geometry- base circle differences, lash (or lack of it), lifter pre-load, block growth (cold vs. hot measurements), rocker wipe on valve (changes desired pushrod length due to shimming/milling rocker pedestal to achieve correct wipe)
For my part- I just suffered a needle bearing failure (with resultant engine failure) in a stock lifter so I'm thinking of getting Comp Rs and running them with stock with somewhere around .020-.040" hot pre-load as Tony suggests.
Thanks
Ben
Originally Posted by JCMGTO
Just wondering if anyone know
s approx how much and LS motor actually would expand with heat. Checking pre-load of lifters. And checked while hot and with seeing all these varying specs was just wondering. I have seen that some have said about .010 difference from hot to cold. My pre-load right now with a dial indicator is .052 Which dependent on whos specs GM's or other manufactuers I would be good or I would be to loose. Since some say GM is .090 to .110. so on a hot engine that would be .080 to .100. And on other specs that would be .020 to .050. So that is why I 'm trying to see. I think it may be the cause for my noise. Since I'm looser then GM specs. Any help is greatly appreciated. Thanks.
s approx how much and LS motor actually would expand with heat. Checking pre-load of lifters. And checked while hot and with seeing all these varying specs was just wondering. I have seen that some have said about .010 difference from hot to cold. My pre-load right now with a dial indicator is .052 Which dependent on whos specs GM's or other manufactuers I would be good or I would be to loose. Since some say GM is .090 to .110. so on a hot engine that would be .080 to .100. And on other specs that would be .020 to .050. So that is why I 'm trying to see. I think it may be the cause for my noise. Since I'm looser then GM specs. Any help is greatly appreciated. Thanks.
Last edited by RX-Ben; May 4, 2005 at 11:35 AM. Reason: more info
