Measuring PR length is best but...7.4s, LS6 milled .040, Cometic .040, Comp lifters?
01-11-2007, 09:47 AM
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Measuring PR length is best but...7.4s, LS6 milled .040, Cometic .040, Comp lifters? I had a problem with the engine that required pulling the heads. While they are off, I am having them swap the .052 GM gasket for a .040 gakset and having the TSP LS6 heads milled down .040". Before milling, the valvetrain noise was pretty obnoxious. Will the 7.4 length pushrods be a more optimal length now?
To recap:
Old Setup: TSP LS6 Heads Unmilled, GM MLS .052", Comp Lifters, 7.4" Pushrods
New Setup: TSP LS6 Heads Milled .040", Cometic .040", Comp Lifters, 7.4" Pushrods
To recap:
Old Setup: TSP LS6 Heads Unmilled, GM MLS .052", Comp Lifters, 7.4" Pushrods
New Setup: TSP LS6 Heads Milled .040", Cometic .040", Comp Lifters, 7.4" Pushrods
01-11-2007, 12:40 PM
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Originally Posted by pianoprodigy
I had a problem with the engine that required pulling the heads. While they are off, I am having them swap the .052 GM gasket for a .040 gakset and having the TSP LS6 heads milled down .040". Before milling, the valvetrain noise was pretty obnoxious. Will the 7.4 length pushrods be a more optimal length now?
To recap:
Old Setup: TSP LS6 Heads Unmilled, GM MLS .052", Comp Lifters, 7.4" Pushrods
New Setup: TSP LS6 Heads Milled .040", Cometic .040", Comp Lifters, 7.4" Pushrods
To recap:
Old Setup: TSP LS6 Heads Unmilled, GM MLS .052", Comp Lifters, 7.4" Pushrods
New Setup: TSP LS6 Heads Milled .040", Cometic .040", Comp Lifters, 7.4" Pushrods
I would say that you would end up just about right.
Hammer
01-11-2007, 12:44 PM
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Your best bet is to follow this:
https://ls1tech.com/forums/generation-iii-internal-engine/637577-katech-how-check-lifter-preload.html
Andrew
https://ls1tech.com/forums/generation-iii-internal-engine/637577-katech-how-check-lifter-preload.html
Andrew
01-11-2007, 12:53 PM
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Originally Posted by thehammer69
I would say that you would end up just about right.
Let's say your lifter preload originally was .080". Then you installed the unmilled heads and larger camshaft. If your smaller base circle of the new cam is any where similar to one that was being discussed recently at CF, then you lost in the neighborhood of .045" radius off the base circle. So you were running in the neighborhood of .035" of preload and being noisy. Now, you are milling your heads .040" and using a .010" thinner head gasket. So now add the .050" back onto your estimated previous .035" and you are now at .085". That puts you within the tolerlance of .075"-.100".... so I think you will be good.
Hammer
01-11-2007, 08:40 PM
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To give you a reference, I have 243's milled .010 with a TR 224/224 114 .563 lift (base circle is .030 smaller than stock??), .045 cometic gasket, and my preload with 7.4's came to be .080 which is right within spec as I understand.
So basically I think you're pretty close.
So basically I think you're pretty close.
01-12-2007, 01:06 AM
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How do you guys come to this conclusion?
1- What was your preload initially?
2- What is the base circle on your cam?
And BTW do you have valve reliefs and what are your cam specs/lobes?
What if initial preload was in .060 range?
Either answer these Qs or measure.
But i would say you are gonna need shorter p-rods.
1- What was your preload initially?
2- What is the base circle on your cam?
And BTW do you have valve reliefs and what are your cam specs/lobes?
What if initial preload was in .060 range?
Either answer these Qs or measure.
But i would say you are gonna need shorter p-rods.
