VINCE

iTrader: (1)

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..

Grimes

iTrader: (3)

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.

405HP_Z06

iTrader: (11)

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":

VINCE

iTrader: (1)

So my guess of .045 was not far off. .040 is around the max?

vettenuts

iTrader: (4)

Have you measured the install height without shims? You may find you are not 1.800 to begin with. Shim from there to the height that Aaron specified above.

Ryan02SS

iTrader: (3)

I agree. The manufacturers numbers are only close. I have found the numbers are usually 7-10psi off at the spec installed height. I deal with high rpm marine motors and the best thing you can do is to shim to .060" before CB stack assuming your setup is up to the task. It eliminates alot of resonation frequency with the spring opening and closing leading to better valve control in most cases.

That's alot of seat pressure for hyd roller lifters when shimmed but necessary for the setup. What lifters are you running?

405HP_Z06

iTrader: (11)

.060 before CB is the max. You will also need to confirm retainer to seal clearance at the proposed installed height.

VINCE

iTrader: (1)

I am running the Cadillac Lifters..

El_Diablo

iTrader: (9)

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.

JPH

iTrader: (2)

He has enough pressure now imo, for his current cam profile.

ls2 bait

iTrader: (11)

whats the purpose of shimming springs? i have patriot extremes on my tfs heads with a comp lsl lobe cam.

LS1Formulation

iTrader: (13)

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.

JPH

iTrader: (2)

I take it your just the driver?

405HP_Z06

iTrader: (11)

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.

ls2 bait

iTrader: (11)

and that means?........if your saying i dont do my own work then yes i do. but my heads came preassembled so i had no reason to learn how to do that yet so im asking questions...

SweetS10V8

iTrader: (4)

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"

Your term for float, I call lofting.

Not saying Im right or anyone is wrong, this is just what I see typically.

405HP_Z06

iTrader: (11)

So we agree on what 'valve bounce' is.

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.