Spring theory
I know someone must have had this thought already…… but.
Larger springs are not needed in the true “box stock” motor.
You only need a spring large enough to close the valve at the max RPM
A higher rate will produce more friction, making less power.

We run on asphalt with a top RPM @ 5000. No one is floating the valves.
We are running the better filter and a pipe.

Last night I took apart 2 motors that have run all season. I was looking for some major loss in the spring rate. That’s not what I found.
The springs were clearly shorter then springs from a new motor.
But the rate at install height (.808) was only 1 pound less then new springs.
The rate at max lift (.602) was also only 1 pound less then the new ones.
All the springs measured 9 and 10 lbs at installed height, and 16 and 17 lbs at max compression.

The big problem I did find was the valve lash.
The lash on the old motors were over .012, it started the year at .004.
That could be a problem.

Later,
Gundy

the lash could be a couple things is it wear on the valve,the rocker, the stud stretching or is it the loss of spring height thats causing the extra lash.thats where the problem needs to be addresed i know i checked mine for the first time after 3 races and it was at 6. so tightened them to 3 and was to tight motor wouldn't start. so went to 4 and it ran but now it floated valves at 5600 where i ran 5700 the first 2 races. so back it back off to 6 and worked alot better.

I think you are correct about the springs. I only want a spring that is strong enough to keep the valves from floating at any RPM below where the engine can breathe well enough to make usable horsepower. Seems to me that any pressure beyond that is a waste of power.

Using stock retainers with stock valves (changing nothing but springs) you will have the approximately the same installed height on both the intake and the exhaust. That is why the springs are the same for both sides. Here are some seat and nose numbers that I have recorded with different springs.

New Stock Springs:
Seat - 10.2 lbs
Nose - 20.4 lbs

Used Stock Springs (10 races):
Seat - 8.8 lbs
Nose - 18.0 lbs

The engine did not make any more power with the new springs, in fact, the change was barely noticable. A side note, if you use the stock exhaust retainer with the intake valve, you lose 1 lb at the seat.

Here are some results with other springs:

Animal Springs:
Seat - 10 lbs
Nose - 49.8 lbs

HP Springs (#DJ-1056)
Seat - 25.8 lbs
Nose - 60.6 lbs

HP Springs (#DJ-1061) I like these springs best on both sides when using the stock cam with a billet flywheel air filter adapter and high flow pipe. (approx 6500 RPM)
Seat - 15.0 lbs
Nose - 50.6 lbs


"18 lb" Honda Springs (They look similar to Raptor springs.)
Seat - 16 lbs
Nose - 26 lbs


Below, I Switch to the HP retainers and keepers (#DJ-1046) and here is what I got: (This is what I like for the superbox engine approx 7800 RPM)

Intake side with intake valve and #DJ-1056 spring:
Seat - 21 lbs
Nose - 56 lbs

Exhaust side with exhaust valve and #DJ-1061 spring:
Seat - 21 lbs
Nose - 56 lbs

Valve spring shims can be added to increase the pressure.
Your results may vary from mine, but the seat/nose pressure relationships are the main thing that should be taken from this.