[C2] Adjusting solid lifters
Thread Starter
Race Director
Joined: Jul 2018
Posts: 10,520
Likes: 8,234
From: San Antonio, TX/Mahopac, NY
2024 Corvette of the Year Finalist - Modified
2024 Corvette of the Year Finalist - Unmodified
2023 C7 of the Year Winner - Modified
Adjusting solid lifters
Anyone have Duke’s updated paper? My L72 has an LS6 cam and I believe both lifters are not actually on the base circle when the relevant piston is at TDC on the power stroke. His paper has updated lash specs and the procedure for which valves to adjust every 90 degrees of engine rotation.
Le Mans Master
Joined: Sep 2002
Posts: 6,569
Likes: 2,401
From: Redacted
Anyone have Duke’s updated paper? My L72 has an LS6 cam and I believe both lifters are not actually on the base circle when the relevant piston is at TDC on the power stroke. His paper has updated lash specs and the procedure for which valves to adjust every 90 degrees of engine rotation.
Last edited by FLYNAVY30; Aug 23, 2021 at 08:32 AM.
Thread Starter
Race Director
Joined: Jul 2018
Posts: 10,520
Likes: 8,234
From: San Antonio, TX/Mahopac, NY
2024 Corvette of the Year Finalist - Modified
2024 Corvette of the Year Finalist - Unmodified
2023 C7 of the Year Winner - Modified
Thanks, Greg, much appreciated!
I could have sworn this paper included the bbc cams and specs. Anyone?
I could have sworn this paper included the bbc cams and specs. Anyone?
Melting Slicks
Joined: Jan 2018
Posts: 2,017
Likes: 2,179
From: Bellevue, WA
2023 C2 of the Year Finalist - Modified
2020 C2 of the Year Finalist - Unmodified
Another option is to use the EO/IC method..... When the Exhaust starts to open, adjust the Intake. When the Intake starts to close, adjust the Exhaust. Yes, it requires rolling over the motor more, but it works.....
Race Director
Joined: Jan 2003
Posts: 17,639
Likes: 3,653
From: Central Arkansas
This is the method I’ve been using as of late. At first I thought it would take forever but it seems to actually go pretty quickly. I usually draw out a sketch showing the cylinder layout, firing order and intake/exhaust valves and just go through each cylinder and record the value on each valve as I go and it goes pretty quick with minimum chance of confusion.
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,264
The LS6 cam is the same as the L-71 cam, which is the same as the L-78/78 cam except this early cam has an oil groove in the rear bearing. The same lobe is used on both sides. If you didn't have a machine shop cut that groove in the later cam your L-72 would have seized up long ago.
For the '65 L-78 the recommended valve lash was .020/.024". For '66 and later it was increased to .024./028". I don't' know why. I do know that the clearance ramp height on the lobe is .012", and 1.7 x .012 = .0204".
Like small block rockers the big block rocker ratio is not constant, but I don't have a reliable data set of rocker ratio behavior through the full range of lift.
Duke
For the '65 L-78 the recommended valve lash was .020/.024". For '66 and later it was increased to .024./028". I don't' know why. I do know that the clearance ramp height on the lobe is .012", and 1.7 x .012 = .0204".
Like small block rockers the big block rocker ratio is not constant, but I don't have a reliable data set of rocker ratio behavior through the full range of lift.
Duke
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
