Valve Spring Pressure and Cam Selection.
Thread Starter
Registered User
Joined: Aug 2001
Posts: 874
From: Carlisle, PA
Valve Spring Pressure and Cam Selection.
Before I start, I know that Valve springs should compliment the cam and other valve train components and not the other way around.
Background info:
I have a set of stock heads with the CM 612 valve springs, locks and retainers.
closed pressure 130
open pressure 340
Install Height 1.768 (stock height)
I also have a set of CNC heads, ported.
They came assembled from previous owner
(383 with a pretty big cam 248/254 on a 114)
It doesn't seem right but these dual coil springs are shimmed and only have 150 closed and 300 open pressure.
What am I missing here?
Do dual coil springs run a lower pressure?
Just trying to sort this whole thing out before I make a cam purchase.
BTW, these springs are said to be able to handle .700 lift.
I'm pretty confident that all the info is legit because the seller has been very helpful so far.
I just don't think I understand how all of this information works together.
Thanks
Background info:
I have a set of stock heads with the CM 612 valve springs, locks and retainers.
closed pressure 130
open pressure 340
Install Height 1.768 (stock height)
I also have a set of CNC heads, ported.
They came assembled from previous owner
(383 with a pretty big cam 248/254 on a 114)
It doesn't seem right but these dual coil springs are shimmed and only have 150 closed and 300 open pressure.
What am I missing here?
Do dual coil springs run a lower pressure?
Just trying to sort this whole thing out before I make a cam purchase.
BTW, these springs are said to be able to handle .700 lift.
I'm pretty confident that all the info is legit because the seller has been very helpful so far.
I just don't think I understand how all of this information works together.
Thanks
Last edited by GetaZforgetGT; Nov 17, 2003 at 10:52 AM.
Moderator
Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
I am not sure I understand your question. There are single and double springs with seat pressures and spring rates that are all over the map. Look at http://www.compcams.com/Technical/Ca...L/324-339.html for example and check out the wide range of springs.
When you list 300lbs of "open" pressure, you need to specify the spring rate (or how far the spring is compressed to get 300lbs), otherwise it's impossible to say if the dual spring is stiffer than the CM spring.
Rich Krause
When you list 300lbs of "open" pressure, you need to specify the spring rate (or how far the spring is compressed to get 300lbs), otherwise it's impossible to say if the dual spring is stiffer than the CM spring.
Rich Krause
Thread Starter
Registered User
Joined: Aug 2001
Posts: 874
From: Carlisle, PA
Yeah I kinda figured I wouldn't have all the needed info.
The numbers I have for CM 612 springs were given to me by the guys at Combination Motorsports.
The numbers I was given for the springs on the heads I just received were given to me by the previous owner.
I honestly have no idea to what degree either spring was compressed to get the numbers.
The numbers I have for CM 612 springs were given to me by the guys at Combination Motorsports.
The numbers I was given for the springs on the heads I just received were given to me by the previous owner.
I honestly have no idea to what degree either spring was compressed to get the numbers.
Registered User
Joined: Dec 1969
Posts: 3,499
From: PORTLAND, OR, MULTNOMAH
Check the Cam Card to see what pressures and installed heights are recommended.
I don't think its a good idea to go much higher than what the cam card recommends since it takes power to compress the springs.JMHO
I don't think its a good idea to go much higher than what the cam card recommends since it takes power to compress the springs.JMHO
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