Box Stock

Take a guess how much HP gain with illegal springs !!!

M

Mr angery

Member
First let me state that any motor leaving our place has legal springs set between .815 to .820 Installed height.

With that said, I have always wondered what gain was there with some heavier ones as we have all seen people tossed on them but yet I had no idea how much of a HP advantage they were getting from them. Never pursued it because we don’t run them but finally had some free time to test.

The springs for the test, 1.65 lbs over at .850 and 2.65 lbs over at .650, in and ex. The Cam- CL2R, The motor has 11.6 peak HP with legal springs. Inertia wheel with Treds pro software.

Take a guess at the ## before I revile them if you wish.

Take a guess at what RPM the heaver spring started adding HP,
And how much gain in HP at
5900
6300
6600
and 6900 RPM

Add any comments you want but I will not knowledge if its some stupid crap about a misspelled word or improper use of a word or any other bla bla bla that don’t pertain to the information above.
 
5900= 0 gain
6300= .4 gain
6600= .7 gain
6900= 1.8 gain

There's my guess. This will be interesting to see what is the real answer.
 
I would say there was no gain up to the point where the legal springs float. Then minimal gain beyond that point until the illegal springs float.
 
My guess is they wouldnt start showing gains until 6600-6700, and would only be a tenth or 2 gain at most. I have watched an engine dominate several classes in a night, then during the spring tech, the springs seem to be well below the legal limit, the dead weight fell flat down, no bounce no nothing, i wasnt sure how that engine would turn more than 6000rpm with those springs but he was turning well beyond that, i can say for a fact because i was behind him turning 6800. As long as the spring isnt allowing valve float, its doing its job, just my opinion on that
 
Keep the comments coming
I know there are more that have input to share then have posted.
I will post results tomorrow at noon ishh but before then lets get more dialog going dammit LOL
 
I’m betting this guy is right on the money:

Kart43 said:
I would say there was no gain up to the point where the legal springs float. Then minimal gain beyond that point until the illegal springs float.
Click to expand...

I’m going to go out on a limb and guess:

5900 – 0 gain

6300 – 0 gain

6600 – 0 gain

and 6900 RPM… <drum roll> ….. a 0 HP gain.

Until the valves float, you should not gain HP, you will gain rpms on the top end, which depending on cam profile, carb size, head flow, valve sizes etc. you may not even have enough flow to produce more HP at higher revs.
Since a CL-2 is designed for 6200-6700 max RPMs not likely you will gain much on the top end.

Theoretically if the springs were stiff enough, these more than likely will not be near stiff enough (something more like the 55# springs) there is a possibility of some slight parasitic drag (maybe immeasurable) that may even cost HP on a relatively stock engine and may also cause accelerated valvetrain wear.
___________________________________________________
Take a guess at what RPM the heaver spring started adding HP.

My guess is they never did. Might add 100-200 rpm, but no HP.
 
Kart43 said:
I would say there was no gain up to the point where the legal springs float. Then minimal gain beyond that point until the illegal springs float.
Click to expand...

That's what I say as well^^^.. Actually, I predict a loss of lower rpm power with the illegal springs...
 
Last edited:
I think the only reason for stiffer springs would be to ensure valves close at a higher then normal rpm. Until you get above what ever is considered a normal rpm, compressing stiffer springs I think would have to eat hp, not make hp. I think cams would also be set to operate and put output within a certain range of rpm, the same as the springs. Unless the cam used is in reality able to make useful hp above the range possible with softer springs, I think there would be a loss of hp and not any gain. If I'm right the stiffer springs would only be beneficial, if cam's already allowed would already work well at higher rpm ranges. To check engine potential, I think it's probably a lot easier to test springs, then to degree cams. It would take more time to prove a cheater cam then cheater springs. Or are cams an open non tech item?

my guess: stiffer springs will mean a loss of hp through out current operating range, but will allow for a higher rpm. If current engines are limited in rpm due to springs, there's nothing to compare hp output too, at additional rpm's.

I think torque output along with hp output, along with rpm; with and without the stiffer springs, would be more telling.

edit; I think it will be very interesting, when you give us the numbers you got with the stiffer springs. I hope my guess about the results is right, otherwise I'll have to do a bunch of shuffling of stuff I don't want to shuffle. ... :)
 
Last edited:
Al? It's not complicated, only people have differing opinions on what would happen if you put heavier springs on an engine.
The assumption is that the engines limiting factor is the valve spring pressure. If that is true, the engine will make more power with better springs. If it's not true, the engine won't. Simple as that.
Build an all out modified engine and put 10lb springs on it and yes you will gain a lot, build a stock engine and put 35lb springs on it and you'll probably lose power due to the increased resistance.

I don't have a guess because I don't have enough experience with clones, however I traced a spring related issue on a SBF to Comp cams sending the wrong springs with the cam one time. It's issue? It would spin to 7400 in 1st, but only about 6100 in second and 6000-6100 in third. The springs would ocillate and float the valves enough to lose seal and stop the rev if accelerating slow, when there was a lot of rpm per second (first or neutral) it would push through it and actually still made power from 6800-7400. Neutral flash would easily hit 8000. (yes I was getting tired of chasing the problem)

In other words, springs don't stop valves at a certain rpm like a switch, they ocillate and lose seal (power) and then as the rpm keeps going up they finally cannot seal the cyl enough to make enough power to further accelerate and the engine "flatlines" During this time the valve are doing crazy things and can kiss the piston etc. And by bouncing off the seat, I mean multiple times per closing event.

In my SBF example, once past the "bad part" the springs closed the valve properly after getting out of the harmonic's range. The engine pulled hard to 7400 and passing the 6000 or so spot "sounded weird" but still pulled albeit a bit less than before and after. Like a dip in the powerband. This was a harmonics issue more than worn out or weak springs so it's a bit different than the "change the springs" we're dealing with on this clone.
 
Last edited:
I have a question. I think the only spring pressure needed is enough to follow the cam opening and closing at the desired rpm.

Great thread and if I'm thinking right, any more is not only not needed, but will hurt engine performance and probably engine longevity.

Which just threw me another question.

What makes valve springs fail. In my 40+ years of experience working on hundreds of different kinds of mechanical equipment all requiring springs, I was always told and taught that if a spring is properly rated, it never wears out.

If clone springs are weakening after x amount of races, there not the right springs. That is unless your using weak springs to enhance performance, knowing they will need to be replaced often. Properly sized springs never wear out, only abuse hurts a springs longevity. maybe?????????????????? ... :)
 
You must log in or register to reply here.
Back
Top