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Flat tappet and valve spring pressures. #14243
02/09/05 11:48 AM
02/09/05 11:48 AM
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HardcoreB Offline OP
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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.
Re: Flat tappet and valve spring pressures. [Re: HardcoreB] #14244
02/09/05 01:07 PM
02/09/05 01:07 PM
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I just added to my original post. A guys got to take a break from typing/thinking sometimes for work related distractions. Again my intent is to refer alot of the Q's to a good archived reference.

Re: Flat tappet and valve spring pressures. [Re: HardcoreB] #14245
02/09/05 03:45 PM
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I was running a racer brown stx22 with a set of lunati springs P/N 73124 and it didn't work 136 seat and 355 open that cam has 276 @ .050 and 590 lift 1.5 rockers .630 with 1.6 It floated the intake valves and ruined them . I then switched to a lunati P/N 73121 140 seat @1.940 400 open. We shimed them to get 150 on the seat and 410 open. This worked to controll the valves but it started to wear the cam after a season. Same cam stx 22 had cam turned into a mushroom lifter cam Had schubeck composite mushroom lifters made. This worked great zero cam wear and was able to control the valves. Finding the right spring combo is an absoltue nightmare if your not going to run schubeck lifters or a roller cam. Flat lobes ruin engines, droped valves from floating valves ruin engines. I done both and it really hurts the old wallet. I don't know yet what this new combo is going to do we will find out soon.

Re: Flat tappet and valve spring pressures. [Re: HardcoreB] #14246
02/09/05 03:46 PM
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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'd run them at 1.850 installed ht. which = 145 lb. I never ran a .600 net lift flat tappet. I used to use a Lunati .600 gross lift cam. That had a net lift of about .550". That gave me an open force of 365 lbs. The engine could go as high as 7600 before valve float using steel retainers. I generally used original max wedge adjustable rockers (not the garbage ones that MP sells). I never removed the inners to break in the cam. I'd think, maybe, you could go to 400 lbs. open with a cam that has been broken in. One thing worth mentioning, is that if you use 1.6 or higher rocker ratios, you'd have to back the spring down by a proportional amount to prevent wiping the cam.

Re: Flat tappet and valve spring pressures. [Re: HardcoreB] #14247
02/09/05 05:12 PM
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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.
Re: Flat tappet and valve spring pressures. [Re: SuperStocker] #14248
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I know of some super/stock racers with bbc engines running schubeck lifters at 250 on the seat and 600 open.

Re: Flat tappet and valve spring pressures. [Re: B1Ken] #14249
02/09/05 05:39 PM
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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.


1993 Daytona, 5.50 at 130mph (1/8) 1.19 sixty ft (PG). Link to 572 B1 - Part 1
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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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
Re: Flat tappet and valve spring pressures. [Re: fast68plymouth] #14251
02/09/05 11:14 PM
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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.

Re: Flat tappet and valve spring pressures. [Re: Locomotion] #14252
02/09/05 11:33 PM
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My $.02...

Ran .904"-type .546" solid on the street w/ 125 closed / 330 open for about 5000 miles and the lifters & lobes looked perfect. RPM limit for me w/ that cam was approx. 6200 (engine started to fall off much past 6000).

Ran the same company's .904"-type .560" solid (one step up from the other cam) on the street for a little over 1000 miles using springs w/ approx. 140 seat / 380 open. Break-in was done "text book" w/o inner springs, etc. Car ran perfectly for the first 900 miles or so, then dropped off 3 tenths & 3 mph between two weekends at the track. Turned out it started eating lobes by that point and even the ones that hadn't started going flat (two were really bad) showed indications of bad things to come.

Switched to Schubeck lifters after that. Current spring is the Lunati 73121 set up w/ approx 150 closed / 400 open for a .600" lift cam. Valve train on dyno looked pretty well under control right up to 7000 rpm, plus no hassles w/ the break-in ordeal.

To be blunt, I'm scared to run an aggressive solid anymore w/o Schubecks. I know plenty of people who don't want to shell out the additional money for 'em, but one bad experience w/ a wiped cam (and the subsequent expense associated w/ going back through the engine as a result) has me big-time gunshy about wiping cams again w/ normal lifters.

Re: Flat tappet and valve spring pressures. [Re: BradH] #14253
02/10/05 01:30 AM
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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
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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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
Re: Flat tappet and valve spring pressures. [Re: fast68plymouth] #14255
02/10/05 09:58 AM
02/10/05 09:58 AM
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Direct Connection did recommend the Triple battleship spring to be used on the 316/.654 mushroom cam. I ran that combo and never wiped a lobe. However, I did break both cams behind the first two lobes. Both cams broke the weekend before the Bracket Finals, what a hassle. Now I run the UD 277/.640 and Isky 8005A springs and have had no problems.

Re: Flat tappet and valve spring pressures. [Re: fast68plymouth] #14256
02/10/05 10:00 AM
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Thanks for all the info, Dwayne!

I have Schubecks on mine now.
As for spring pressures, Comp Cams recently came out with a larger OD beehive spring. As you may know, you can use quite a bit less spring pressure with the same application because of their design.

I forgot the # at the moment, but I believe it ends with "120" and it's something like 1.44" in diameter at the base.

Re: Flat tappet and valve spring pressures. [Re: fast68plymouth] #14257
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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.

Re: Flat tappet and valve spring pressures. [Re: fast68plymouth] #14258
02/10/05 10:57 AM
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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.


1993 Daytona, 5.50 at 130mph (1/8) 1.19 sixty ft (PG). Link to 572 B1 - Part 1
Re: Flat tappet and valve spring pressures. [Re: 440Jim] #14259
02/10/05 02:08 PM
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HardcoreB Offline OP
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I almost hate to chime-in because the thread is evolving the way I hoped it would. Thanks for everyones input. I am curious to know if any of the applications that require pressures beyond 380 lbs. over the nose are using steel retainers and or mufflers (backpressure). What dia. pushrods and wall thickness in those applications? Are the applications exceeding 380 lbs. (nose) with success using synthetic oil after the break-in period? I am beginning to think the best recommendation to give someone whos combination of parts see significant gains above 6500 rpm (e.g.-1's heads on a 446") is to use a roller cam. (In retrospect isn't that the consensus already.)

Re: Flat tappet and valve spring pressures. [Re: 440Jim] #14260
02/10/05 03:42 PM
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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.

Re: Flat tappet and valve spring pressures. [Re: HardcoreB] #14261
02/10/05 03:45 PM
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If your part of the in crowd (I'm not) you will hear run a roller. But not from me. I'm not into the cookie cutter engine crowd. Roller lifters belong in a pratt&whitney 1340 radial engine. This had outa get some responses right b1ken? Lol

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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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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