Increase Pushrod Length = Tune?
Thread Starter
Instructor
Joined: Aug 2016
Posts: 112
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From: Colorado Springs
Increase Pushrod Length = Tune?
LS7 was tuned with 7.775 two years ago, recently measured the pushrods and to get ~0.070 preload, the pushrods need to be ~50 thousand longer.
Will the tune need to be updated or will the ECM account for the increased flow in/out?
Thanks in advance.
Jim
PS: How did I get here? AHP gave me pushrods as part of their heads/116 cam kit and I assumed they would be correct. When measuring for valve wiggle, I measured the lengths for 0 lash. Some of the preloads were only 15 thousand, so I opted to increase the length for the correct preload.
Will the tune need to be updated or will the ECM account for the increased flow in/out?
Thanks in advance.
Jim
PS: How did I get here? AHP gave me pushrods as part of their heads/116 cam kit and I assumed they would be correct. When measuring for valve wiggle, I measured the lengths for 0 lash. Some of the preloads were only 15 thousand, so I opted to increase the length for the correct preload.
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Joined: Sep 2013
Posts: 3,102
Likes: 1,271
From: Harbor City California
You do not need to tune when changing pushrods. All changing pushrods does is change preload of the lifter plunger.
the stock LS7 hydraulic lifters have a max plunger depth of roughly .180" or so.
This means that you can technically run any preload over zero and under .180". With that said ideal preload depending on who you talk to is anywhere form .070"-.130".
GM likes to be around .130" from the factory with most aftermarket re-builders preferring to be around .080"-.110" (like we do).
If you shoot me a PM with your email address I can shoot you over a quick check sheet so you can check your rough preload when your installing your rockers.
https://americanheritageperformance.com/
the stock LS7 hydraulic lifters have a max plunger depth of roughly .180" or so.
This means that you can technically run any preload over zero and under .180". With that said ideal preload depending on who you talk to is anywhere form .070"-.130".
GM likes to be around .130" from the factory with most aftermarket re-builders preferring to be around .080"-.110" (like we do).
If you shoot me a PM with your email address I can shoot you over a quick check sheet so you can check your rough preload when your installing your rockers.
https://americanheritageperformance.com/
Thread Starter
Instructor
Joined: Aug 2016
Posts: 112
Likes: 12
From: Colorado Springs
Interesting article on pushrod length impacting power.
http://www.superchevy.com/how-to/eng...nd-performance
Supporting Vendor
Joined: Sep 2013
Posts: 3,102
Likes: 1,271
From: Harbor City California
Last edited by American Heritage; Mar 11, 2020 at 10:27 PM.
