441 is the spring rate, in lbs/in...not the open pressure. It is listed as 155 lbs @ 1.850" closed height, and 420 lb @ 1.250" open height, with coil bind @ 1.195" height.

Since as a rule you don't want to go closer than .050-.060" of the coil bind height, that leaves the 1.250" open height as the max this spring can accommodate.

If we take .570" lift and work backwards, this gives us a minimum installed height of 1.820" in your application....so your thoughts of going to the 1.825" installed height by way of just a .015" shim is right on target.

No way will it work at 1.780" height though, so you got to make that shim change...and make sure you've got retainer to seal/top of valveguide clearance for more than the original .540" lift rating.

It will increase your closed height pressure by 11 lbs(.025" difference from 1.850" listed spec x 441 rate/in = 11.02), which is perfectly acceptable and what I'd want anyway, the 155 lb seat pressure doesn't give much leeway to prevent valve float if rpm should get away from you for some reason and the additional seat pressure helps there.

You're good, but right at the limit of that spring so no putting a 1.6 ratio rocker on down the road without a different spring at the same time. :thumbup:

 

What is the coil bind for the 977-16 valve springs? You must have at least .060” between each coil at .570” valve lift.

977-16 valve springs
155 lb @ 1.850” seat load
441 lb @ 1.280”. (.570” valve lift) open load

Option:
190 lb @ 1.780” seat load
476 lb @ 1.280”. (.570” valve lift) open load

That is acceptable with a roller camshaft. Steel valve seat inserts and the rest of the valve train must be right with that much valve spring pressure.

 

What is the coil bind for the 977-16 valve springs? You must have at least .060” between each coil at .570” valve lift.

And the misinformation from you just never stops, you do not need .060" clearance per coil.....any spring company will tell you that is a total spec for the entire spring.

977-16 valve springs
155 lb @ 1.850” seat load
441 lb @ 1.280”. (.570” valve lift) open load

Per Comp Cams Catalog, spring is 441 lbs rate per inch....spec at 1.250" open height is listed as 420 lbs. It will only be 406 lbs at 1.280"

Option:
190 lb @ 1.780” seat load
476 lb @ 1.280”. (.570” valve lift) open load

I don't know where you got this from....and the math doesn't even add up.

That is acceptable with a roller camshaft. Steel valve seat inserts and the rest of the valve train must be right with that much valve spring pressure.

Are you ever going to post reliable information??

If the #977-16 spring is set up at 1.780" seat height and used with a .570" lift cam it is going to be just .025" from coil bind....that is too tight. Coil bind is listed as 1.195" as I posted previously.

 

I just realized that i did not mention that the valve locks on the heads are +.050 7* , what is the purpose of using the +.050?, sorry

 

This raises the retainer in relation to the lock groove on the valve, so it gives you +.050" more installed height than you would get with a standard dimension valve lock.

 

A word of caution for those using self aligning rocker arms. You cannot use +.050” up locks with self aligning rocker arms.

 

.010 to .020 between coils is adaquate. Self-guiding rockers on cam's over .530 lift especially were high RPMs are involved is not a good idea, if the spring looses control the valve then the rocker can be left to fend for itself this can have unpleasant consequences.

Bogie

 

Rather than just being “adequate”, I prefer a safety margin of .100” between the coils at maximum valve lift. That is in case of spring surge at high RPM which can lead to broken valve springs and disastrous engine damage if the engine swallows a valve.

 

well i took a used spring and retainer and put it in the vise, tightened it to coil stack up, backed it off until i could get a .060 feeler between the the middle coils but the end coils were still stacked tight, backed it off until i could get the feeler between end coils but now the center coils are way over a .100", going to pull rocker cover off one of the heads that are on my other engine and do some measuring at full lift,thanks

 

i pulled cover and checked clearance at full lift, max lift for those heads are.520",
the cam lift is .495", i have approx .020" between coils, a little more in the center coils, so my original post should be good to go
, thanks

 

Practical experience with coil bind.

I had a 1969 Pontiac Firebird 400 with a Ram Air IV camshaft. That cam had stock regular production dual Pontiac valve springs that set up at 1.600” with coil bind at 1.100” or .500” valve lift.
The Ram Air IV camshaft has .520” valve lift with 1.65:1 Ram Air IV rocker arms and .470” with 1.5:1 rocker arms.
I broke a valve spring and a week later I broke another one. I was using stock production 1.5:1 rocker arms. I was lucky.

I replaced the stock production valve springs with 1967 Ram Air valve springs that set up at 1.720” with coil bind at 1.100” and used 1.65:1 Ram Air IV rocker arms. No more problems with broken valve springs.

That was back when you still had to use genuine Pontiac Parts.