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Discussion Starter #1
Hey guys, tried search bar but no luck. I'm in the middle of rebuilding my frankinsten 96,99,2003 turbo cobra. Gotta love the mod motor! Haha. Have forged crank, Manley rods, Manley flat top pistons. Looking to run around 15 psi of boost. Will the stock valve springs in my 99 heads be safe? It's going to be mostly a street beast. thanks, Jon
 

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I was running stock springs at 10psi. But now it's built, i got comp. beehive springs. Seat pressure is what u need it worry about. So u won't have valve float.

I believe my engine builder said that the stock 2v springs are 60lbs of seat pressure.

My comps are 120 lbs


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Discussion Starter #5 (Edited)
I've heard if you do go with comp springs its best to go ahead and do stainless valves too. Heard the stiff springs can actually break the stock valves. Just didnt know how strong/good the stock valves and seat pressure are. Guess that's still cheaper then having to rebuild it again. Thanks, Jon
 

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It's possible but i know most guys don't do the valve upgrades.


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Discussion Starter #7
Thanks man, i appreciate it. I'd like to do just springs if that's a safe route. I'm going to go ahead and time-sert the heads while they are off as well.
 

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If it's 2v no , you need 120lb valve springs like comp cams , if your head is 4v then yes.
 

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Discussion Starter #9
It's a 4 valve. Heads came off a bone stock 99 cobra. They have 78,000 miles. So valve seat pressures are ok for mild boost on the 4 valve? Just not the 2 valves?
 

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It's a 4 valve. Heads came off a bone stock 99 cobra. They have 78,000 miles. So valve seat pressures are ok for mild boost on the 4 valve? Just not the 2 valves?
Yeah for 4v it's fine , just 2v you will have valve float . I had 90lb comp cams valve springs that floated, now I have 120lb and problem solve.
 

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Discussion Starter #11
Sweet! Thanks guys. Ill end up doing the springs. Just for piece of mind. Hear it's the exhaust side thats the main problem. Just wasn't sure how good the stock ones were.
 
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