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Valve spring question

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bullerman

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We run Predators here under Gulf Coast and NELA rules. Alot of us run the Dyno Cl2 cam. Under NELA rules you have to run the 10.8 valve springs. Under Gulf Coast you can run 18lb springs.
My question is would you want the springs as weak as they can be and still pass tech. Never seen them check springs here. A lot of people want to put the 18lb springs in thinking it will help
In the old Flathead days we had controlled valve float. I watched ARC video on valve springs. He says he sets them at 10.9 and after a couple of races they get weak. I assume if you ran them five races they would be less than 10.8. So if your springs get less than 10.8 is it better but against the rules. I think he called some if the springs builder springs. I guess they come strong and he sets them to 10.9. Just wondering.
 
10.8 is the maximum installed height pressure allowed by the rules.

With ohv engines, the objective is to set the intake valve down on seat without having it bounce. Ie, controlling the valve motion.

More pressure allows the engine to turn more rpm before bounce occurs. So setting at max allowed pressure is preferred.
Unless, more spring pressure robs more power than the gain in rpm creates.

So, the best possible choice would be the least pressure that allows you to get to desired rpm without valve bounce.

Without actual dyno numbers to see whether you are losing power to valve bounce, or excess pressure, most simply set to max pressure allowed by the rules.
 
Just asking. I put my motors together. I use the green and white springs that are supposed to be preset but I don't know about that.
I just wondered if less than 10.8 spring pressure is an advantage. I change springs maybe twice a season. Thanks for the information. Very informative.
 
Here in the uk, gx engines are sealed. Engine builders can ask ££££ for a blueprinted engine, one thing that's addressed is the valve spring, they bulk buy from Honda and check every single one, selecting the stiffest. This sort of blueprinting commands top dollar for an engine, and keeps the builder in business.
 
95 shaw said:
10.8 is the maximum installed height pressure allowed by the rules.

With ohv engines, the objective is to set the intake valve down on seat without having it bounce. Ie, controlling the valve motion.

More pressure allows the engine to turn more rpm before bounce occurs. So setting at max allowed pressure is preferred.
Unless, more spring pressure robs more power than the gain in rpm creates.

So, the best possible choice would be the least pressure that allows you to get to desired rpm without valve bounce.

Without actual dyno numbers to see whether you are losing power to valve bounce, or excess pressure, most simply set to max pressure allowed by the rules.
Click to expand...
Never really thought about it but if you are teched the valve spring can't be more than 10.8 lbs or less than 10.8.lbs at .850 installed height. I don't think they would ever be checked around here at our local tracks.
When i ran Flatheads I would take some bathroom scales and put them on my drill press. I woild take a lifter and put it in the drill press. I would set the stop on the drill press at my installed height and check how many pounds of pressure it was on my bathroom scales. Kind of crude but I think it worked. We were trying for controlled valve float back then.
Wish I did own a dyno. It would be fun to experiment.
 
Valve spring cannot be more than 10.8 at .850 installed height.

Dyno Don has some pics and video of the tech tools on his website.

Search his posts here for the web address.

I started karting when you had to run Briggs specific springs in the correct position.

We had to run Briggs rods, pistons. And that dreaded stamped steel dipper.

The dipper effectively limited rpm to 6000.

6200, for very long created windows in the front of the block.
 
bullerman said:
We run Predators here under Gulf Coast and NELA rules. Alot of us run the Dyno Cl2 cam. Under NELA rules you have to run the 10.8 valve springs. Under Gulf Coast you can run 18lb springs.
My question is would you want the springs as weak as they can be and still pass tech. Never seen them check springs here. A lot of people want to put the 18lb springs in thinking it will help
In the old Flathead days we had controlled valve float. I watched ARC video on valve springs. He says he sets them at 10.9 and after a couple of races they get weak. I assume if you ran them five races they would be less than 10.8. So if your springs get less than 10.8 is it better but against the rules. I think he called some if the springs builder springs. I guess they come strong and he sets them to 10.9. Just wondering.
Click to expand...
Gc rules are 10.8 springs, not sure where you got 18lb at
 
I believe the rules say 10.8 or 18lb for Gulf Coast. Look at Mohave rules. Mohave, Savage Battlecreek and BJ'S all run NELA and Gulf Coast rules. See if I am looking at the rules right. I don't know for sure. I put a photo of the valve spring rules.
 

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That's the same spring at different heights.
Still 10.8# @ .850 height.


Gulf coast rules just more involved tech.

Can have no more than 18# @ .650 height.
 
I believe I see now. When the 10.8 valve springs installed at .850 are compressed to .650 it can't be more than 18 lbs. That makes sense if thats right.
Sorry Bodydropped.
 
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