This math doesn't work out...

Trickflow spring:
125 lbs. @ 1.780" installed height
376 lbs. @ 1.180" open
420 lbs. per inch rate

So at .600 lift, it's 376 lbs..

Comp 987 spring:
121@1.8 install height
388@1.2 open load
344 lbs/in

So at .600 lift, it's 388lbs..

Explain to me how, a spring that is less lbs at seat, and less lbs per inch, can be higher at the same lift? Now personally, I calculated both of them based on (lift x rate) + seat, and came up with 377 for the trickflows, and 327lbs for the comp 987's at .600 lift.. wtf Is comp's published numbers off?

I'm trying to figure out if I can use my lighter trickflow springs. The above mentioned ones are beating the snot out of my cam bearings.

Trickflow springs i'd like to use:

120 lbs. @ 1.780" installed height
300 lbs. @ 1.280" open
360 lbs. per inch rate

With my .540 lift cam, it should be 314lbs open with these, vs 306lbs open
with the comps, if the comps are actually 344lbs per inch. So either comps published open pressure is wrong, their published spring rate is wrong, or my math is wrong.

-- Joe

 

That would all depend on what height you have them installed at, what lift they coil-bind at as a result of where they're installed, and how much lift you're ACTUALLY putting on them.

Neither of those is good enough for .600" of lift, really. .575" for the 987s, maybe, if set at EXACTLY their design installed height; the TF springs probably about .550 - .560". If you're running them past that, and/or with less installed height, then you're into the danger zone. On the other hand, if you're running them with more installed height, you probably have valve float.

However all that may be, the Comp spring works out to 445 lbs/in AVERAGE over the .600" spec they give, based on (388-121)/.600. Which compares about where one would expect with the equivalent specs that TF gives. AFAIK the seat/open #s are right, I've never measured the "rate" for those springs though.

Nowhere near enough to damage cam bearings I wouldn't think; at least, not without smearing the lobes off first.

Incidentally, the car I drove yesterday has 987 springs but only about .530" of lift, set up at 1.800" + or - about .010", they seem to get along just fine.

 

The TrickFlow springs ae actually 418 lb/in by their numbers. The Comp springs are actually 445 lb/in by the advertised measurements, not 344.

Beyond that, and despite metallurgists and engineers best hopes, spring wire (and most other steel) does not present a constant resistance rate to deflection. The metallurgy and heat treatment can get it fairly close to a linear rate, but as the deflection distance increases, the resistance (force) increases slightly in a somewhat asymmetrical function, up to the point of shear. For the purposes of a valve spring, however, the quoted spring rates are a generally adequate guide.

That Comp spring is a heavy *****.

 

Bah! My springs are a little soft at about 180 pounds on the seat. I want new ones with around 250 pounds on the seat. Of course I'm also running a big roller cam with .740 lift.

As for your spring choises. Find one that's close to the seat pressure at whatever the installed height is and will allow the cam to open the valve without spring bind. Spring bind is normally the open rate less .060" but can also be closer to .100". If your cam doesn't open the valve to the open rate, then you're fine. You can always shim up the 1.8" installed height to 1.78" to increase the seat pressure but you'll also decrease the amount of lift before spring bind.

All 3 springs you listed are close enough to use. Pick the one you like and use it.

 

Well I called both trickflow and comp.. Looks like if I use the lighter springs it will be 120lbs installed, and about 314lbs at full lift with a 08-306-8 cam (.540 lift).. Comp says that pressure sounds fine as long as there is plenty of clearance for coil bind.

Trickflow posts on their website that that spring is capable of .540 lift max.. I wonder if thats .540 lift with .060" clearance, or what. (industry standard, no?) Trickflow doesn't know what they coil bind at, he told me to measure it myself.. thanks *******.

Since the heads are machined with locks and retainers for a 1.780" install height, if I get valve float i'll have to switch to comp 987's and get some +.020" valve locks to get the 1.800" install height..

-- Joe

 

Sounds to me like you'd be running the TF springs RIGHT ON THE HAIRY EDGE. Which is never a good idea, if you can help it.

I believe it would be wise to just go ahead and get the Comp ones, now, before something evil happens.

They don't make +.020" valve locks; .050" increments only.

Get +.050" ones, and .030" shims.

 

Ugg. I didn't realize that.. wtf

I think i'll break the motor in with the lighter springs.. Run it no more than 3500rpm for a few oil changes, then change the springs over to the comp 987's. You're right.

I should also measure the spring pockets to make sure trickflow's not full of **** with there 1.780" install height

-- Joe

 

3500 RPM won't help you much, if they coil bind.

I believe I'd proceed directly to the final solution, bypassing unnecessary intermediate steps that lead to disaster.

If you're running a flat tappet cam and feel the need to run a lighter load, then take the inners out of the 987s for break-in. If you're running a roller (as you are IIRC?) then you don't need to worry about reduced spring pressures for break-in at all. Jus tput it together right, once, and leave it that way.

Checking the installed height yourself is ALWAYS a good idea.

Valve Spring Mic

 

They won't bind at 3500. If they have .060" of clearance at max lift they wont bind.. Maybe float at 6500 rpm if the springs dont have enough pressure.

-- Joe

 

Preventing valve float isn't to have a high open pressure but to have a high enough closed pressure so that the valve doesn't bounce on the seat when it slams closed. With a cast cam, you can't get too aggressive with spring pressures or it will break the cam. Keeping it close to the cam's recommended pressures is good or maybe slightly higher.

It you have a billet cam, go higher on the seat pressure especially if you're buzzing the engine to a high rpm.