SFT cam valve spring question - 460 Ford Forum
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post #1 of 8 (permalink) Old 04-18-2017, 07:21 PM Thread Starter
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SFT cam valve spring question

Working on a new stroker. Going to be running a solid flat tappet cam. Little over 600 lift. Looking at trying to make it live a while. Street driven car, not a daily by any means, but will see some miles. Question I guess, is at what kind of spring pressures do things get bad? Probably super open ended question. Lunati recommended a spring that was about 325 lbs at the nose, 125 at the seat. Seemed like the guy was kind of throwing it out there. Someone I trust a lot more recommended a spring with about 130 seat and 400 at the nose. Big difference and just wondering what was safe? Engine won't see the north end of 6000 rpm. Any insight would be appreciated.
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post #2 of 8 (permalink) Old 04-18-2017, 07:25 PM
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Working on a new stroker. Going to be running a solid flat tappet cam. Little over 600 lift. Looking at trying to make it live a while. Street driven car, not a daily by any means, but will see some miles. Question I guess, is at what kind of spring pressures do things get bad? Probably super open ended question. Lunati recommended a spring that was about 325 lbs at the nose, 125 at the seat. Seemed like the guy was kind of throwing it out there. Someone I trust a lot more recommended a spring with about 130 seat and 400 at the nose. Big difference and just wondering what was safe? Engine won't see the north end of 6000 rpm. Any insight would be appreciated.

Cam part number and specs?

Engine build parameters and cylinder heads induction?



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post #3 of 8 (permalink) Old 04-18-2017, 07:50 PM Thread Starter
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Cam specs are 241 in. 247 ex. at .050. .599 in. .606 ex. lift 108 lobe separation ported dove heads 2.19 1.76 valves going in a 521 , occasional mud races, street terror. Just for fun truck.
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post #4 of 8 (permalink) Old 04-18-2017, 09:25 PM
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Cam specs are 241 in. 247 ex. at .050. .599 in. .606 ex. lift 108 lobe separation ported dove heads 2.19 1.76 valves going in a 521 , occasional mud races, street terror. Just for fun truck.

Comp 930-16 spring package is a good match here. You do NOT need 400# over the nose with this cam, Dove heads at 521 inches as it will peak below 6K rpm.

Any SFT cam that we have utilized that needed more than 400# over the nose got high zoot EDM lifters. We have run some boss 302 vintage class stuff at near 440# open for 7,300 rpm peaks.




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post #5 of 8 (permalink) Old 04-18-2017, 09:42 PM Thread Starter
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Thanks. Kind of what I was wanting to hear. 400 seemed like a little more than I felt good running. I did spring for some micro polished edm lifters. Nice pieces. Seemed like good insurance.
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post #6 of 8 (permalink) Old 04-18-2017, 10:18 PM Thread Starter
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Looking at those springs. Seat is a bit higher than other springs with the same nose. Just curious as to how that affects things, if it does, and if you feel like answering questions
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post #7 of 8 (permalink) Old 04-19-2017, 12:44 PM
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Looking at those springs. Seat is a bit higher than other springs with the same nose. Just curious as to how that affects things, if it does, and if you feel like answering questions
There are two separate issues when addressing valve train control. One is valve bounce when the valves are closed rapidly with aggressive lobe profiles (seat pressure). The second is lofting the lifter as it traverses the nose of the cam lobe (open pressure).

I like a bit of additional seat pressure to minimize bounce. 140# seat in your application is fine.

When breaking in your cam You will remove the inner springs, use good assembly paste on the lobes and lifter crowns as well as a proper break in oil for flat tappet cams.



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post #8 of 8 (permalink) Old 04-19-2017, 02:21 PM Thread Starter
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Thanks for the explanation. Appreciate the input as always.
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