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Old 10-29-2002, 11:29 PM   #1
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valve springs too stiff... what can happen?

If you are using a low lift flat tappet cam, hydraulic lifters... what would happen if the valve springs were too stiff? Do lifters play a significant role in oil pressure?

I am getting some chatter when the engine is hot and I'm at an idle. Not too bad, but I'm trying to figure out why. My oil pressure is good... 64psi cold, 52psi cruising 2000 rpm's, and at hot idle 38psi.

I'm wondering if I have a lifter collapsing when the oil gets hot. I did have one bad lifter in this new set when I built the engine... maybe another is going bad.

could this happen??

Thanks!

btw. cam lift is under .500 and I am using the tfs spring kit from summit, they are good up to .542 lift

Also, are roller cam valve springs different then flat tappet cam valve springs? Am I gonna have problems using these springs with a flat tappet cam?

Thanks!!
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Old 10-31-2002, 10:02 PM   #2
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bump

anybody???
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Old 10-31-2002, 10:33 PM   #3
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Valve springs are an often overlooked part of the total valvetrain combination. They shouldn't be, as they are as important as any component in the valvetrain, or for that matter, the whole engine.

Generally speaking, there are really not good and bad valve springs, any more than there are good or bad cams. There are only parts that do or do not match the rest of an engine combination, and therefore work well together or not. Certainly there are higher overall quality/durability springs versus economy pieces, but the there is more to it than just getting a "good brand."

Valve springs for flat tappet and roller cams for the same general engine application and rpm will be substantially different. Roller cam springs will generally have both higher seat pressures and higher open pressures; often they further have the ability to handle more lift. This is because the roller on the lifter interfaces with the cam in a geometry that allows both higher ramp acceleration velocity, and reduced lifter/cam friction. The more severe acceleration ramps enabled by roller lifters mean the valve is lifted further for a given duration than with a flat tappet. Higher velocities and greater total valve train range of movement means greater spring pressure is required to prevent valve train separation and valve bounce off the seat.

Roller lifter springs for a hot street, open track, or street/strip motor might have ~140 lb. on the seat and ~340 lb. open. These pressures are well-endured by the roller lifter, but would cause rapid wear on a flat tappet cam designed for the same engine application. Fortunately, the flat tappet lifter is lighter than the roller lifter and can be effectively controlled at somewhat lower pressures.

Both roller and flat tappet hydraulic lifters can suffer partial collapse of the lifter at high rpms with the attendant high spring pressures, especially those of a roller setup. As inertial forces become greater and greater with increasing rpm, at some point the internal plunger of the hydraulic lifter body will begin to collapse down into the body of the lifter as the oil cushion is forced out by the great pressures. High rpm photography/measurements have shown that hydraulic roller setups can lose as much at .050" lift when pushing the rpm envelope. This actually changes the effective duration of the cam (the .050" specs) and helps to explain the performance difference typically found between otherwise valve-motion-equivalent solid and hydraulic tappet cams. This phenomenon rapidly increases in severity as the spring pressures required to control the valve train reach and exceed 350 lb. open pressure. You don't need this kind of pressures for these applications with a flat tappet cam, and you should avoid any spring pressures higher than necessary. This is one of those places where more isn't better.

Best plan is not to guess at valve spring requirements. Only the cam grinder can specify the ideal springs for a particular grind. More than just pressure specs, the springs must effectively control the particular range of harmonics generated by the unique lobes of any given grind. Only the cam grinder will have data/tests to accurately match up a given grind with suitable springs/dampers. You may get lucky taking an educated guess based on lifter type, cam lift/duration, and rpm range intended...but why set yourself up for potential failure when the advice for the right specs is free from your cam supplier?

Steve A.

Last edited by amossm; 10-31-2002 at 10:37 PM.
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Old 10-31-2002, 10:48 PM   #4
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whew amoss!! he's got ya covered here. basically, too much spring pressure will collapse the lifter...not what you want to happen. and no, i don't think the lifters will affect oil pressure significantly at all. good luck with it. see ya, jb
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Old 11-01-2002, 05:07 PM   #5
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I am currently waiting a solid roller cam from FTI. The motor i bought from XXX (some company who I rather keep quite right now since they are working with me on this situation). The cam is a hydralic roller in a 408 with AFR 205's. The valve springs have a seat pressure of 210 closed. Basically i have a solid roller spring rated for .670 lift on a mid .550 hydralic cam. My engine rwtq is awesome, but my rqhp sucks. I came to the conclusion through the help of Ed Curtis that my combonation was off and i was not getting the proper lift and was probly collapsing some lifters as well. I hope to have my solid roller installed soon and should see the kinda of rwhp #'s associated with a big inch motor like the one i have.

Good Luck with your project because i know what u are going through right now.......
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Old 11-01-2002, 05:23 PM   #6
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Quote:
Originally posted by Clint Mumford
The valve springs have a seat pressure of 210 closed.

I came to the conclusion through the help of Ed Curtis that my combonation was off and i was not getting the proper lift and was probly collapsing some lifters as well.
Yep, that's what I was talking about. 210 lb. on the seat likely means "omygod" open pressure from a hydraulic lifter's perspective. With Ed's solid cam, bet your motor pulls very strong like before through the torque peak and then really wakes up right where it used to go to sleep on top.

Steve A.
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Old 11-01-2002, 06:01 PM   #7
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Trick Flow Spring Kit...

I also have that TF spring kit (from Summit). I did some research on the springs and from what I understand, you don't want giant numbers on roller-lifters. I emailed TF (because they only gave the closed pressure @ 1.800 installed height - 110 lbs. ) I was told they have a .500 lift pressure of about 260 lbs. The Crane springs run like 375 lbs @ .500 - and was told that was way too much for the stock roller-lifters... Mark
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Old 11-01-2002, 10:41 PM   #8
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375lbs too much?...... he**, I run 440lbs open pressure on race hyd. rollers all the time. Because of the velocities of the roller cams being used, open pressures of 375-400 lbs should be the norm on good performance 5.0's being turned 6000 RPM +. If the valve train separates during high speed operation, the beating put on the parts (rockers, valves, locks, retainers, etc.) is 10 times worse than the stress created by the extra spring pressure. A couple rules to remember.... high seat pressure requires good valves, locks and retainers that will take the stress of hitting the seat with the extra pressure on them. Open pressure is limited on flat tappet cams by the material (cast iron) used in the cam and the lifters. Too much pressure will wipe out the lobes or even break the cam in extreme situations, however, we are taling about 425 + pounds of open pressure (which, incidently, is the pressure we run on NASCAR late model 2 barrel engines with .600 lift flat tappets and 1.9:1 rockers, although some special oiling tricks are used to keep these applications alive).
When in doubt..... use more spring!

HiTech
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Old 11-04-2002, 10:06 AM   #9
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Apples and Oranges...

HiTech - this post sorta went off on a tangent... While I'm no valve-train expert - you're talking about NASCAR and race roller lifters. Both Trick Flow and my machine shop said the "normal" seat pressure needed for a "steet app" is 100-120 lbs. And the Trick Flow kit was designed for a direct bolt-in stock (E7 head) replacement with about 260lbs @ .500 lift.

I actually don't know how much pressure is required for a stock 5.0 roller turning 6k. But apparently, 250-270 does the trick. (I only run mine to about 5500.) I certainly can't disagree that you may need 350-450 lbs on your race motor - but I was just talking about (what I was told) on a stock 5.0 with stock lifters... Mark
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Old 11-04-2002, 11:48 AM   #10
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My point is that unless you use so much pressure as to wipe out a flat tappet cam, high pressure springs do not cause problems..... and they certainly have no effect on oil pressure.

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Old 11-04-2002, 12:32 PM   #11
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I'm just saying, match the app...

I agree on the oil pressure, but there's no reason to run "high pressure" springs that are good to 7500 rpms on a street motor. More pressure means more friction, which means more wear and parasitic drag = less power.

Again - I really don't know how much I need, but I assume since the TF kit was made as a stock 5.0 replacement, they should be good to the 6250? rev limiter. Mark
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Old 11-04-2002, 01:00 PM   #12
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Re: valve springs too stiff... what can happen?

My opinion


Quote:
Originally posted by Nitro_Snake
btw. cam lift is under .500 and I am using the tfs spring kit from summit, they are good up to .542 lift
With springs for up to .54" lift with a cam a little under .50" you'll be fine.

Quote:
Originally posted by Nitro_Snake
Also, are roller cam valve springs different then flat tappet cam valve springs?
In a nut shell, roller cams require stiffer springs because of the weight of the roller lifters.

Quote:
Originally posted by Nitro_Snake
Am I gonna have problems using these springs with a flat tappet cam??
No

Last edited by white86coupe; 11-08-2002 at 08:07 PM.
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Old 11-04-2002, 01:13 PM   #13
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Re: Re: valve springs too stiff... what can happen?

Quote:
Originally posted by white86coupe
With springs for up to .54" lift with a cam a little under .50" you'll be fine.
That's only half the story..... the lift figure is in refference to the spring's coil bind height, but pressure is just as critical. My LS1 stock eliminator motors have only .500 lift cams but those springs wouldn't be even close to adequate to turn the engine over 6000.


Quote:
In a nut shell, roller cams require stiffer springs because of the weight of the roller lifters.
Actually, rollers require more pressure because of the higher valve velocities created vs. a flat tappet cam.

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Old 11-04-2002, 01:36 PM   #14
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Mark, not to disagree but the TFS T/W springs are light for a reason. The heads are designed to be a bolt-on for flat tappet cams as well.

Most cam companies I talked to felt the TFS T/W springs would be inadequate at anything over 5700 rpm with 1.6 or 5400 rpm with 1.7. They said I ran the risk of bent valves. They are okay for a "E" cam or Wolverine but are not enough for grinds like Comp Cams XE-HR. I know several people who have run into problems with them with TFS Stage 1 cam and 1.7 which is the real reason TFS recommends against the 1.7 with that cam.

If you want to run a aggressive hydraulic roller. The Track version springs are a better match for most aggressive HR cams.

Ford says the max presssure for the factory lifters is 135 lb / 400 lb which incidently happens to be very close to what comes on the FMS / FRPP 392 crate motor with the Comp Cams XE282HR.

The TFS stock head upgrade kit is not overly stiff for Cams like the Comp Cams XE series of flat tappet cams.

Call the cam company and give them the specs on the springs and ask if they are to much. If pressure is to high you can change the installed height for a moderate reduction. You will have to change the locks and/or retainers for this. Every 0.05 change in installed height will drop seat pressures 15 lb.

You did check lifter preload when you did the install didn't you?
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Old 11-04-2002, 01:57 PM   #15
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Quote:
Originally posted by V8Pinto
Mark, not to disagree but the TFS T/W springs are light for a reason. The heads are designed to be a bolt-on for flat tappet cams as well.

Most cam companies I talked to felt the TFS T/W springs would be inadequate at anything over 5700 rpm with 1.6 or 5400 rpm with 1.7. They said I ran the risk of bent valves. They are okay for a "E" cam or Wolverine but are not enough for grinds like Comp Cams XE-HR. I know several people who have run into problems with them with TFS Stage 1 cam and 1.7 which is the real reason TFS recommends against the 1.7 with that cam.

I couldn't agree more. I learned the hard way very recently that springs may not work even though they are rated for more lift then the cam produces. I recently had to order a new set of Comp Cam springs for my TW heads. I have a Bennett cam with a max of only .513 lift. The stock springs on my TW heads could not handle this cam even though its rated to .540 lift. My motor was suffering from valve float above only 5,200 rpm's. Reason for this is seat pressure. Stock TW have a seat pressure of 110 lbs new. My cam needs 140 lbs. This is due to the aggressive ramp rates of the lobes on the cam. Someone already mentioned that valve springs also need to be matched for the combo. That hit the nail on the head.
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Old 11-04-2002, 02:03 PM   #16
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V8Pinto...

V8Pinto quote: You did check lifter preload when you did the install didn't you?

Are you asking me this? No, I did not. The machine shop installed the springs @ 1.800" which was supposed to give me a seat pressure of about 110. I've got 1.7 stud mounted (adjustable) rockers with the stock .444 lift cam. My shift point is always at or below 5200. (It pretty much quits pulling at 5000.)

Why would I have too much lifter preload with these springs if I added 1/2 turn on the rocker nut after zero lash?

Thanks for any input. Mark ('86gt)
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Old 11-04-2002, 02:28 PM   #17
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Re: Re: Re: valve springs too stiff... what can happen?

Quote:
Originally posted by HTMtrSprt
Actually, rollers require more pressure because of the higher valve velocities created vs. a flat tappet cam.

HiTech
How is there going to be "higher valve volocities created" if the flat tappet cam and the roller cam have the same lift, duration ect...?

The weight of the lifter does play SOME role in a roller cam needing more spring pressure.

Not trying to argue, just curious.
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Old 11-04-2002, 02:36 PM   #18
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Mark, I was talking to the original poster who has a zero-lash valvetrain (0r at least didn't mention converting his GT40ci). I should have specified. He has the TFS stock head upgrade kit which is the same pressures as the T/W springs.
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