TOO MUCH VALVE SPRING

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CFD244

CFD244

"I LOST MY ID IN A FLOOD"
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Hi Folks

I picked up a nice set of O heads fresh from the shop. The heads have brand new 995 comp cams dual valve springs, new retainers, and new 10 degree locks. Seller had bigger plans for these heads than I do. The cam I am installing only profiles a .470 lift. Hydraulic flat tappet with 273 adjustable valve gear.

Comp cams recommends 901's. 1.65 installed height and a spring rate of 330. The 995's have an installed height of 1.70 and a spring rate of 402.

I'm running a 340 auto with 3.23's and a 2500 stall.....A cruiser.

Does anyone foresee a problem with running "overkill" springs? I have them, and they are ready to bolt on.

Thanks
 
As cheap as 901s are, I wouldn't chance it. JMO
 
I just installed Comp 901's in my 273 Commando along with a 340 AT cam. Excessive spring pressure will increase wear of the entire valvetrain. 65'
 
CFD244 said:
Hi Folks

I picked up a nice set of O heads fresh from the shop. The heads have brand new 995 comp cams dual valve springs, new retainers, and new 10 degree locks. Seller had bigger plans for these heads than I do. The cam I am installing only profiles a .470 lift. Hydraulic flat tappet with 273 adjustable valve gear.

Comp cams recommends 901's. 1.65 installed height and a spring rate of 330. The 995's have an installed height of 1.70 and a spring rate of 402.

I'm running a 340 auto with 3.23's and a 2500 stall.....A cruiser.

Does anyone foresee a problem with running "overkill" springs? I have them, and they are ready to bolt on.

Thanks
Click to expand...
Just up the height to 1.70 if it isnt already=115 and open @240ish if that-chry geometry issue.
They're a versatile spring you can use with hyd, solid, hyd roller IF set up right.

They're fine properly setup. They are what you call a step up in performance.
 
MOPAROFFICIAL said:
Just up the height to 1.70 if it isnt already=115 and open @240ish if that-chry geometry issue.
They're a versatile spring you can use with hyd, solid, hyd roller IF set up right.

They're fine properly setup. They are what you call a step up in performance.
Click to expand...
Are you referring to the 901's or the 995's?
 
I explored designing/creating an active spring system for engine value trains. The idea was to use a spring material that more easily collapses to open valve. But then becomes ridged under electric field to close value at timing. 20 years ago the materials were available, but not strong enough to stand up to engine valve stress. The idea of course was to greatly reduce valvetrain stress, thus increase engine efficiency and performance.

I thought I would throw the idea around for maybe a younger mind to pickup and maybe follow up on material advancements as well has newer engineering concepts.

We can always use a better spring design for many applications.
 
not an engineer but I like to read...
this would be the cats meow/solving all spring/valve issues


upload_2022-4-21_12-29-14.jpeg
 
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The 995 is 402lb/in.
So, 402 x net valve lift + seat force = open force.

402 x .450” lift = 181, + 115(seat) = 296lbs(open).

If you can get more height, both numbers would go down a bit.

This assumes the heads have had the spring seat step modified for the inner spring.
 
Two drawbacks to running too much spring pressure. First, as others have mentioned is wear and load on the entire valvetrain. Keep in mind that the cam sees the open pressure times the rocker ratio. So 300# open pressure is 450# at the cam lifter interface with a 1.5 rocker, placing greater load on the oil film (insert zinc debate here).

The next is a bit more subtle, but still important especially on a street engine. It simply takes more energy to compress a stiffer spring. This is $4/gal energy that isn't turning the driveshaft. Pure parasitic loss. Worse, it rises exponentially with RPM, and is proportionally greater at lower power settings like cruise.
 
Only a few people have shown the math to get the loads, and those loads make it obvious that it's a non-issue. I vote run 'em. I'd rather have a little too much than a little too little, IMHO. The modest difference won't affect a darn thing on a hot rod.

If you plan to make frequent coast-to-coast trips, or put it in a truck and never rev it over 4k, the calculus on the decision might be different.
 
If the heads are set up for the 995’s(spring seats modified), and the installed height is at least 1.700....... it wouldn’t bother me to use them.

Remove inners for cam break in.
 
Take out the inner spring or raise the installed height another .050 to 1.750. But u first need to know where your at right now. The machinest should know. Kim
 
oldkimmer said:
Take out the inner spring or raise the installed height another .050 to 1.750. But u first need to know where your at right now. The machinest should know. Kim
Click to expand...
How would you raise from 1.7 to 1.75 if the space under the retainer is only 1.7?

Edit: 120 psi seat, and 300psi @ 1.180 (this open height was the lift these springs were originally chosen for. My lift is substantially lower).
 
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U can change the retainers or locks to change the installed height. Were they set up with these numbers? Then u will have substantially less psi at max lift. So u should be good to go. Kim
 
oldkimmer said:
U can change the retainers or locks to change the installed height. Were they set up with these numbers? Then u will have substantially less psi at max lift. So u should be good to go. Kim
Click to expand...
These numbers were set for a .550 lift. My cam is .470.
 
CFD244 said:
Are you referring to the 901's or the 995's?
Click to expand...
The 995
Go to comps spring chart and look at the pressures per lift. 1.70=115lbs seat
Open at your lift is not 300 lbs. You have to wrap your mind around the idea that even though the springs are setup to run a .550 lift...to get the pressures you listed..would actually take .550 lift to attain...you're at .470.. you're looking at less than 300...like 250 or so open. There fine.
The 901 could work...but when they wane over time like springs do..they'll let you know with valve float and hammered seats from bounce. There just inst much room with those. 105 seat or something... in a year that'll be 90-95 lbs. The 901 is also right near the limit for that lift.
Stick with the 995.
 
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Thanks for everyone's input. I will run the 995's. A little overkill, but they are installed and ready to go. Great news.

Best regards to all.
 
You shouldn't remove the inner spring. The springs are an interference fit, purposely made that way to stop spring surge, which could cause loss of control of the valvetrain.
 
Bewy said:
You shouldn't remove the inner spring. The springs are an interference fit, purposely made that way to stop spring surge, which could cause loss of control of the valvetrain.
Click to expand...

For break-in he absolutely should remove the inner spring....
 
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