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Street strip valve spring pressure? #2714701
11/11/19 02:09 AM
11/11/19 02:09 AM
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Between a rock & a hard place
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cudadoug Offline OP
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cudadoug  Offline OP
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How much spring pressure are you street strip guys getting away with? Especially a drag week type of motor.

Is 240/600 # too much spring....???

Re: Street strip valve spring pressure? [Re: cudadoug] #2714724
11/11/19 08:54 AM
11/11/19 08:54 AM
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Prospect, PA
BSB67 Offline
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Going out on a limb, this is a solid roller. Seems a little backwards not starting with the cam lobe profiles and rpm range to pick your springs.

If you are using spring pressure to back into your cam choice, a lot of folks seem to use that type of spring on street cars. I think the comp 943 spring is commonly used.

Last edited by BSB67; 11/11/19 08:56 AM.
Re: Street strip valve spring pressure? [Re: BSB67] #2714760
11/11/19 10:53 AM
11/11/19 10:53 AM
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Between a rock & a hard place
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cudadoug Offline OP
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I'm fiddling with an already built motor and I'm trying to determine if the (solid roller cam) valve train will live on the street. Yes, it has the Comp 943 spring.

Re: Street strip valve spring pressure? [Re: cudadoug] #2714781
11/11/19 11:49 AM
11/11/19 11:49 AM
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Posts: 33,754
Bend,OR USA
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Cab_Burge Offline
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Hopefully the motor builder modified the oil system so it oils the rocker shafts and valve springs full time luck scope
If not that is needed on any motor that will be ran on the street for any length of time, the extra oil helps keep the valve spring temps down so they live longer work up
As far as the pressures I like form 250 LB+ to 325 on the seat and from 600+ up depending on the valve lift and max RPM the motor will be ran at work
To many racers use to little seat pressure and end up damaging the rollers at the max RPM due to the wheel not staying on the lobe over the top at max RPM, you can see skidding on the back side of those lobe, it will look like two narrow tracks on the outside edges of the lobes scope tsk


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Street strip valve spring pressure? [Re: Cab_Burge] #2714785
11/11/19 12:00 PM
11/11/19 12:00 PM
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Posts: 3,175
Between a rock & a hard place
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cudadoug Offline OP
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depending on the valve lift and max RPM the motor will be ran at

Good point. I don't see the need to take this bullet past 6500 for what the ET goals are.

Re: Street strip valve spring pressure? [Re: cudadoug] #2714800
11/11/19 12:27 PM
11/11/19 12:27 PM
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State of confusion
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Thumperdart Offline
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About where I'm at w/a .680.660 Isky solid roller in the mid 9's for several years w/one lifter rebuild and spring swap......


72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
Re: Street strip valve spring pressure? [Re: cudadoug] #2714837
11/11/19 02:15 PM
11/11/19 02:15 PM
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Posts: 3,350
New York
polyspheric Offline
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Regardless of spring pressure or RPM, high lift beats up the stem-guide contact with thrust at a high angle. There is no way around this (except relocating the entire rocker shaft assembly, and even that does very little), since it's a function of the ratio of the rocker arm's long (valve-side) lever length vs. lift: low numbers are bad.


Boffin Emeritus
Re: Street strip valve spring pressure? [Re: cudadoug] #2714918
11/11/19 06:45 PM
11/11/19 06:45 PM
Joined: Feb 2005
Posts: 3,954
Prospect, PA
BSB67 Offline
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What cam lobes? The 943 can control a lot of lobe profiles to 6500.

Re: Street strip valve spring pressure? [Re: cudadoug] #2714938
11/11/19 07:37 PM
11/11/19 07:37 PM
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Oregon
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AndyF Offline
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Oregon
You need to talk to the cam mfg or someone who has experience with that specific cam lobe. Spring pressure depends on the cam lobe as well as stiffness and weight of the valve train parts.

Re: Street strip valve spring pressure? [Re: cudadoug] #2715105
11/12/19 11:37 AM
11/12/19 11:37 AM
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Posts: 15,198
Val-haul-ass... eventually
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BradH Offline
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Val-haul-ass... eventually
A 240/600 load like a PAC 1243 or COMP 943 "should" be good to 7000 RPM (or higher), as long as the cam's not overly aggressive, the pushrods are stout enough, the rockers are rigid enough, etc.

One (or more) out-of-sync component with the total package and it might not matter what springs you use. And that same caveat likely applies to how things will hold up on the street, too.

Wish I could add more first-hand experience, but with all the delays getting much junk back on the road, I don't have anything to add for long-term durability.


An unskilled person with a "cool idea", a bunch of porting tools, and a set of cylinder heads is a sure recipe for disaster.
I AM that person!
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