Flat tappet and valve spring pressures.
#14243
02/09/05 11:48 AM
02/09/05 11:48 AM
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Joined: Jan 2003
Posts: 4,003 Shelby Twp. Mi
HardcoreB
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Being that this is a FAQ I hope we can accumulate enough good suggestions and successful combinations to warrant archiving. A good benchmark IMO for adequate solid flat tappet spring pressure for 95% of all HiPerf. applications using a solid F/T lifter would be the CompCams #928 with a rate of 350#. This spring @ 1.95"/1.35" (.600" net lift)gives 135#/345# if it is what they say it is in the CC catalogue. Any loads consideribly above or below (10%)the "bench mark" with success? Would like to hear about the more extreme examples if you know what your installed height, camshaft, lash, rocker and retainer used, and max. rpm. IMO if you exceed the spring RATE by 10% of the benchmark you are only asking for trouble. EDIT ADD-At that point I would consider either grooving the lifter bores or using something like what Crower offers with their cool-face lifter.(Hole EDM'd from the face to oil pressurized gallery.) I think where the Schuebuck's may be attractive to some is that they are less prone to lose their crown also, I want to believe their crown may be more optimally ground to begin with than a much cheaper lifter. I would also like to document a reasonable benchmark for a hydraulic flat-tappet.
Last edited by HardcoreB; 02/09/05 12:59 PM.
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Re: Flat tappet and valve spring pressures.
[Re: HardcoreB]
#14247
02/09/05 05:12 PM
02/09/05 05:12 PM
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Joined: Jan 2003
Posts: 990 Vacherie, Louisiana
SuperStocker
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super gas
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From my experiences with conventional flat tappets, you will see cam/lifter wear at ~370lbs/in 'open' spring pressure. Again this is with conventional flat tappets and cams. Now with shubecks, I wouldn't run anything less than 400lbs/in 'open' spring pressure. I rarely worry about valve spring pressure 'on seat' or 'closed'. I choose my springs according to open pressure and let the closed pressure fall were it does. Again, this goes for flat tappets only.
Last edited by SuperStocker; 02/09/05 05:19 PM.
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Re: Flat tappet and valve spring pressures.
[Re: B1Ken]
#14249
02/09/05 05:39 PM
02/09/05 05:39 PM
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Joined: Jan 2003
Posts: 16,916 NC
440Jim
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Quote:
This is not an extreme departure from yours, but I used to use Isky # 8005-A. They have a rate of 400 lb/in.
I have used this spring for 3 years until I changed heads last Sep and needed something else for different reasons. I really liked those springs. I ran them at 140 on the seat and 380 open. The most lift I used was 0.623" gross minus 0.014" lash = 0.609" net with 1.5 rockers.
With the new heads, I ran 150 seat and 435 open on the intake and 150 seat 395 open on the exhaust. I ran a 0.650" cam with 0.028" lash up to 7500 rpm, without issue for a couple weeks (with 1.6 rockers actual net lift was 0.665"). But I now have a 0.620" cam and shift at 6500, trap at 7000. This is a net lift of 0.635" with the 1.6 rockers resulting in 425 open intake, 385 open exhaust and the same seat pressure. Time will tell.
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Re: Flat tappet and valve spring pressures.
[Re: 440Jim]
#14250
02/09/05 10:02 PM
02/09/05 10:02 PM
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Joined: Jan 2003
Posts: 14,478 So. Burlington, Vt.
fast68plymouth
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ive run several flat tappet combos in the 425-450lb open range with no problems.
in fact, IIRC for one of the big flat tappet cams MP was selling i think they were rcommending the big triple spring.
however, i will say i dont feel the lifters of today are as hard as they used to be, and the engine oil doesnt have the amount of zinc it used to either....so what used to work fine, may not be the hot ticket any more.
i also feel the cam design plays a big role in how pressure you can get away with, as well as the rocker ratio.
EDIT- i checked my old MP engine manuals.
they show the recommended spring for the .620 and .655 flat tappet cams is the P3462887 triple spring, which has a rate of 558lbs/in.
157lbs @ 1.900 and 447lbs @ 1.400.
the "mild" MP dual spring(P2806077) has a rate of 530lbs/in(115 @ 1.900, 380 @ 1.400).
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Flat tappet and valve spring pressures.
[Re: BradH]
#14253
02/10/05 01:30 AM
02/10/05 01:30 AM
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Joined: Jan 2003
Posts: 4,448 Phoenix, AZ
MoparBilly
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Wow, Good thinking Hardcore B, I've been running a 304/640 ultradyne solid (fairly agressive) for 3 seasons, 385 passes with the same springs. They are Crower #68346, installed height is 1.920 using the old MP "2 inch" Titanium retainers, yeilding 155 seat and 416 open. Rockers are 1.5 Ductile Iron Isky's...normal shift point is 6500, but it's seen 7550 on spray. I'll be replacing them soon, with another set of identical springs, they cost 145$ from my supplier, so they aren't cheap, but I'm happy with the results!!!
"Livin' in a powder keg and givin' off sparks"
4 Street cars, 5 Race engines
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Re: Flat tappet and valve spring pressures.
[Re: Locomotion]
#14254
02/10/05 09:51 AM
02/10/05 09:51 AM
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Joined: Jan 2003
Posts: 14,478 So. Burlington, Vt.
fast68plymouth
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I Live Here
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Quote:
Are those "regular" flat tappet cams or "mushroom" lifter cams? Wasn't there a metalurgy difference? I also recall something about "chilled iron lifters".
That's an awful lot of spring pressure for a regular solid lifter.
the 620 cam is a std flat tappet cam, the 655 is a mushroom.
they show the same spring to be used for both.
chilled iron lifters need to be run on special cam cores(steel billet or hardface overlay), not the std iron core.
the Cup motors run steel billet cams with stellite filled lobes.....but are required to run std iron lifters.
they are running over 500lbs open pressure.
one key factor in not having a problem with high spring pressures on flat tappet cams is having either the cam or lifter be definately harder than the other. that way there can be no exchange of material between the two parts.
this is the priciniple behind the Schubeck's. the lifters are so much harder than the cam, there can be no exchange of material....so much higher than "normal" spring pressures can be used.
i tried 5 different cams during one season in my old 448 about 20 years ago.
never soft sprung any of them for break in(i never used to bother with that), no failures, reused the lifters on a couple of them.....450ish open pressure.
when i was talking with my connection at Comp he was saying that lifters used to be around 60 on the C scale, but that the stuff available now is closer to 55.
cams are around 50.....so now the cams and lifters are closer to the same hardness.
couple that with the change in the oil addititve packages, and i believe this is the root of why flat tappet cam failures are more common than in the past.
as a measure to help combat this, Comp now offers having the cams be Nitrided as an option to increase the surface hardness.
the fact is, running many of todays more aggressive lobe designs, along with the trend to use higher rocker ratios, using springs that only provide 350-370lbs open pressure will not allow many combinations to rev as high as they need to, to work properly in the car.
many of these bigger, faster cams will make power to well over 7K when combined with decent induction/exhaust systems.....and 350lbs open pressure just wont get you there without getting into valve float in many instances....especially in BB applications where the valves and valvetrain can be on the heavy side.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Flat tappet and valve spring pressures.
[Re: fast68plymouth]
#14257
02/10/05 10:04 AM
02/10/05 10:04 AM
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Joined: Jun 2004
Posts: 1,226 Peoples republic of clackamas ...
atoetly
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pro stock
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The only difference between a standard cam and a mushroom cam is some of the lobes need to be narrowed so they won't interfear with other lifters on the opposing bank. My new cam Racer brown stx42 290@.050 670 lift with 1.6 rockers I'm going to run 170 seat and 480 open and see what she does.
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Re: Flat tappet and valve spring pressures.
[Re: 440Jim]
#14260
02/10/05 03:42 PM
02/10/05 03:42 PM
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Joined: Jan 2005
Posts: 66 Orlando
nickmckinney
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Quote:
I also feel the oil is a factor. I have been using Mobil 1, 15W-50 since that is the only Mobil 1 viscosity that is designed for performance use and "muscle car era" engines. My last two cam break-ins have been using Rotella diesel oil with STP, then switch to the 15W-50. And no inner-springs... Other oils may be good to, but some lack significant amounts of extreme pressure, anti-scuffing, zinc, additive.
idling is bad for a flat tappet with heavy springs too.
Also take a look at Mobile Delvac synthetic (deisel target market) and the Mobile Truck and SUV synthetic. They are both exactly the same once behind the labels from what I hear but the SUV version is cheaper I hear (I can't find it locally yet dammit) They look real good for racing too from the additive specs I have seen.
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Re: Flat tappet and valve spring pressures.
[Re: atoetly]
#14262
02/11/05 09:47 PM
02/11/05 09:47 PM
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Anonymous
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Anonymous
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Now AT, that can't be true because I read an article in National Dragster written by RearEnder and Morrison that claimed that everyone needs a 10,000 RPM roller cam with 780#'s over the nose and 400 seat pressure. They stated that they would be glad to build anyone of us a roller motor for $30K to $40, they take Visa and mastercard.
I think I'll just order one up so I can be...as they stated "In this Century"
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