valve spring strength for mushroom flat tappet cam
#1526979
11/01/13 02:47 PM
11/01/13 02:47 PM
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Joined: Aug 2010
Posts: 208
Munich, Bavaria
docford
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OP
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Posts: 208
Munich, Bavaria
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In the process of rebuilding a 1969 Grand National NASCAR HEMI, I'm going to check the dual valve springs and see if they need to be replaced or not.
Would you know what seat pressure and what open pressure they should have for a mushroom flat tappet P3614436 camshaft ?
Last edited by docford; 11/01/13 02:55 PM.
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Re: valve spring strength for mushroom flat tappet cam
[Re: docford]
#1526980
11/01/13 04:59 PM
11/01/13 04:59 PM
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Joined: Jan 2012
Posts: 2,666
Stuttgart, Arkansas
rickseeman
master
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master
Joined: Jan 2012
Posts: 2,666
Stuttgart, Arkansas
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That cam may have been listed in one of the old MP Hemi manuals. If it was they would have listed the proper MP spring. And it should have the springs specs in there but I'm not sure.
2011 Drag Pak Challenger
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Re: valve spring strength for mushroom flat tappet cam
[Re: rickseeman]
#1526982
11/02/13 05:30 AM
11/02/13 05:30 AM
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Joined: Aug 2010
Posts: 208
Munich, Bavaria
docford
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OP
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Munich, Bavaria
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Quote:
That cam may have been listed in one of the old MP Hemi manuals. If it was they would have listed the proper MP spring. And it should have the springs specs in there but I'm not sure.
The Chrysler HEMI Racing Manual only states a type and part number, but no specs.
It says "battleship" PN P3462887
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Re: valve spring strength for mushroom flat tappet cam
[Re: dwayne welder]
#1526983
11/02/13 05:31 AM
11/02/13 05:31 AM
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Joined: Aug 2010
Posts: 208
Munich, Bavaria
docford
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OP
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Quote:
Once you figure your camshaft spec's, and your retainer size, i would give PAC Racing Valve Springs a call!!! They make the springs in house!!! There are located in southfield, mi. 866-799-9417 Talk to Matt!!! I would NOT use those old spring's!!! You are just asking for proplem's!!!!!!!! Go TO www.RACINGSPRINGS.COM Good luck on your project!! 
Thanks for the hint. We'll measure lift and duration and I'll give them a call 
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Re: valve spring strength for mushroom flat tappet cam
[Re: 23T Hemmee]
#1526985
11/03/13 07:35 PM
11/03/13 07:35 PM
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Joined: Aug 2010
Posts: 208
Munich, Bavaria
docford
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OP
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Quote:
... I will say for right now, until I can find better info for you, do not use the battleship springs for any type of endurance engine, they will not live, period. They were drag only springs and were notorious for breaking even on the trailer if they weren't brought up to operating temps before putting any rpm's to them.
Thanks for the advice
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Re: valve spring strength for mushroom flat tappet cam
[Re: docford]
#1526987
11/04/13 01:45 PM
11/04/13 01:45 PM
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Joined: Jan 2010
Posts: 588
Franklin, TN
23T Hemmee
mopar
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mopar
Joined: Jan 2010
Posts: 588
Franklin, TN
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Doc,
The STX-21 was used mostly on the short tracks, and would probably have a decent torque band for the type of racing you're doing. The bathtub intake was really not the greatest for up and down rpm changes and the short duration camshaft went a long way in keeping the engine cleaner without fouling plugs. One thing you might do, even if you don't run the original springs is go ahead and check the pressures and spring heights, if the pressures are within 3-5% across the board, that should give you a ball-park figure when ordering new ones. When you bought this engine, did it appear that it was ready to go, one way to tell, were the intake bolts allen-heads, and were they safety wired? Does it have the magnesium dry-sump pan or fab-steel? The mag pans were bad about corroding if they sat too long, just something to check.
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Re: valve spring strength for mushroom flat tappet cam
[Re: docford]
#1526992
11/05/13 10:48 PM
11/05/13 10:48 PM
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Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
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Posts: 14,506
So. Burlington, Vt.
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i dont know how high you plan to rev the motor, but that will have a big impact on the spring pressure requirement.
for an old school type cam like what you listed, i would probably start with something around 155 on the seat, and maybe 400-425 open.
unless the motor has some rockers with higher than std ratios, i would expect that pressure would get you close to 7000rpm with that cam.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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Re: valve spring strength for mushroom flat tappet cam
[Re: docford]
#1526996
12/21/13 04:26 PM
12/21/13 04:26 PM
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Joined: Mar 2008
Posts: 883
Affton MO
qwkmopardan
super stock
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super stock
Joined: Mar 2008
Posts: 883
Affton MO
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Quote:
I found out that the installed camshaft is a Racer Brown STX-21.
That is a very good grind. My 383/449 with 915 heads made over 650 HP with the STX-21. 9.02 at 149 at 2500lbs.
145-150 seat and not more than 380 over the nose. If using new lifters I would send it back to Racer Brown for a regrind, about $75. 410-866-7660
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Re: valve spring strength for mushroom flat tappet cam
[Re: qwkmopardan]
#1526997
12/22/13 08:07 AM
12/22/13 08:07 AM
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Joined: Aug 2010
Posts: 208
Munich, Bavaria
docford
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OP
enthusiast
Joined: Aug 2010
Posts: 208
Munich, Bavaria
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Quote:
Quote:
I found out that the installed camshaft is a Racer Brown STX-21.
That is a very good grind. My 383/449 with 915 heads made over 650 HP with the STX-21. 9.02 at 149 at 2500lbs.
145-150 seat and not more than 380 over the nose. If using new lifters I would send it back to Racer Brown for a regrind, about $75. 410-866-7660
That is pretty close to what I did order. Here are my specs:
ISKY-8205-SP Dual Valve Springs with damper 440 lbs./in. Rate
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