Valve spring seat pressure ?

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Oct 20, 2009 | 09:01 PM

AlexB333

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Joined: Feb 2007

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From: Harrisburg Pa

Valve spring seat pressure ?

Hi guys, I have a question for you. I recently finished up my TT engine build and I am having what I think is a valve float problem.

The car made 686whp/736wtq at 5500 and anything after that the car just stumbles and falls on its face. It can't make anymore power after this. I think the springs we went with might be the problem. I went with a double spring from Manley. I am running 16psi and want to go more but need to figure this out.

What seat pressure should I be running? The springs now are 150lb. Also what lifters are you big hp guys running? Also what about switching to solid lifters etc?

Thanks

Oct 21, 2009 | 11:37 AM

corvettebob1

Melting Slicks

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From: Near Jacksonville Fl.

Looks like your losing about 54lbs of seat pressure @ 16lbs of boost, IFIR the stock seat pressure is ~100 lbs.
So I'm just guessing you might be right on the edge of float, I'd contact one of the tuners on this board and see what they say.

Oct 21, 2009 | 11:43 AM

BLOWNBLUEZ06

Tech Contributor

Joined: Apr 2007

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From: Forney Texas

Most dual springs I've seen are ~ 135 closed and 375 open @ .650. I always shim up my springs to raise the closed seat pressure. You can shim it based on true coil bind and your true valve lift. Did it do this on the dyno? If so, you will often times see a huge dip on the graph around 5krpm.

Oct 21, 2009 | 11:44 AM

chriswtx

Le Mans Master

Joined: Feb 2002

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From: San Marcos Texas

I'm running Patriot extreme springs rated at 150lbs of seat pressure. I have them shimmed to approx. 180lbs of seat pressure. I'm running LS7 lifters. I see 18-20lbs of boost up to 7000rpm with no problems..

Oct 21, 2009 | 11:52 AM

BLOWNBLUEZ06

Tech Contributor

Joined: Apr 2007

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From: Forney Texas

I just looked at their master catalog and it shows 5 different springs and 2 of them seem to be double springs. One set is 155-405 and the other is 170-446. Either one of those would work fine. Your problem must be elsewhere. Too many people running Patriot springs with 135-375 seat pressures for that to be your problem.

Oct 21, 2009 | 08:43 PM

AlexB333

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From: Harrisburg Pa

Quote:

Originally Posted by BLOWNBLUEZ06

Well I am thinking that with a low seat pressure and stock lifters that I do not have enough pressure. At 5500 rpms the car starts to stutter and drops on its face. It will lose around 180whp in a matter of a few hundred rpms and you feel the motor flutter but it's not missing.

Thanks

Oct 21, 2009 | 09:22 PM

BLOWNZO6

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Joined: Mar 2001

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From: Knoxville Tennessee

Quote:

Originally Posted by AlexB333

What seat pressure should I be running? The springs now are 150lb. Also what lifters are you big hp guys running? Also what about switching to solid lifters etc?

What part number are you running and what lift is the cam you have?

I am a Manley dealer as well and have run quite of few of these springs.

I always run LS7 lifters.

I would not recommend going with solid lifters but if you decide to, I have a brand new set of Crowers in the box that I will sell you.

I always use LS7 lifters with good pushrods and stock rockers, never have any issues.

If you can tell me what spring you bought I might be able to help you.

Oct 22, 2009 | 03:10 AM

95vettski

Safety Car

Joined: Mar 1999

Posts: 3,613

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From: Toronto, Canada

I'm using patriot extreem springs and ls7 lifters and see 18-20 psi also with no problems. Do you have a boost controller? Maybe try lowering the boost and see if its better?