Need Valvespring Shimming Experts..
Thread Starter
Joined: Nov 2001
Posts: 8,259
Likes: 4
From: Valrico, Florida
Need Valvespring Shimming Experts.. I have a 408ci motor with this cam in it and I am running twin turbos.. 224/230 .609/.604 114LSA +2 (Comp XFI lobes).. I am running Patriot Gold Extreme dual valvesprings in my AFR225 heads...
Install Height: 1.800"
Max. Valve Spring Lift: 0.660"
Spring Pressure Closed: 155 lbs. @ 1.800"
Spring Pressure Open: 410 lbs. @ 1.140"
Coil Bind: 1.090"
Retainer Material: Titanium
My question is what is the safe MAXIMUM seat pressure I can run with this spring? I am guessing somewhere around .045 and what would that bring my seat pressure up too? I hear high boost applications running around 180 to 200lbs of seat pressure..
Install Height: 1.800"
Max. Valve Spring Lift: 0.660"
Spring Pressure Closed: 155 lbs. @ 1.800"
Spring Pressure Open: 410 lbs. @ 1.140"
Coil Bind: 1.090"
Retainer Material: Titanium
My question is what is the safe MAXIMUM seat pressure I can run with this spring? I am guessing somewhere around .045 and what would that bring my seat pressure up too? I hear high boost applications running around 180 to 200lbs of seat pressure..
Well, I would just shim it the max the manufacturer recommends before you risk coil bind - I believe the standard is to shim to within .060" of coil bind, but my memory is not the best, lol. Call up Patriot and ask what the max shim you can run is. That's pretty much it.
Assuming your using 1.7 ratio rocker arms, you would need to shim them to 1.760" to get maximum spring pressure and stay at the minimum coil bind height.
Here's approximately what they would be installed at 1.760":
Here's approximately what they would be installed at 1.760":
That's alot of seat pressure for hyd roller lifters when shimmed but necessary for the setup. What lifters are you running?
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
back from the dead...Are ls7 lifters sufficient for this kind of abuse? I'm the jack *** with the latest 408/F1-C vette build. I'm waiting for my cam specs but I believe Im going to need some serious seat pressure and I don't want to kill lifters.
Joined: Apr 2006
Posts: 3,894
Likes: 1,139
From: Grand Rapids, Michigan
Shimming springs so they have more seat pressure makes them more capable of holding the valve closed once it returns to the seat. If you don't have sufficient seat pressure, the valve can "bounce" off the seat, i.e. valve float.
Valve float is when open spring pressure is insufficient to control valve motion as the valve progresses from open, past peak lift, and starts to close.
Valve spring harmonics play a large part in the equation and must me taken into account when assembling a valve train for an engine combination.
Actually, insufficient closed spring pressure manifests as 'valve bounce' when the spring can't control the valve closing event.
Valve float is when open spring pressure is insufficient to control valve motion as the valve progresses from open, past peak lift, and starts to close.
Valve spring harmonics play a large part in the equation and must me taken into account when assembling a valve train for an engine combination.
Valve float is when open spring pressure is insufficient to control valve motion as the valve progresses from open, past peak lift, and starts to close.
Valve spring harmonics play a large part in the equation and must me taken into account when assembling a valve train for an engine combination.
To me valve bounce is a system that cant control the closing of the valve and it bounces on the closing ramp. I think its also been coined vavle float at the same time. Like how everyone call facial tissue "Kleenex", they seem to term anything that is an out of control system "Float"
Your term for float, I call lofting.
Not saying Im right or anyone is wrong, this is just what I see typically.
I think its a terminology thing myself. I just dont know that everyone agrees with terms.
To me valve bounce is a system that cant control the closing of the valve and it bounces on the closing ramp. I think its also been coined vavle float at the same time. Like how everyone call facial tissue "Kleenex", they seem to term anything that is an out of control system "Float"
To me valve bounce is a system that cant control the closing of the valve and it bounces on the closing ramp. I think its also been coined vavle float at the same time. Like how everyone call facial tissue "Kleenex", they seem to term anything that is an out of control system "Float"
Lofting is a very common characteristic of many agressive cam lobes. The difference between valve loft and valve float is that valve loft is controlled and valve float is uncontrolled.
