Will stiffer valvesprings eat hp?

crazypete · Aug 12, 2005

I just finished ordering an FTI cam and it calls for 200 lb seat pressure double springs in leiu of my stock 120 pounders. How much does valvetrain spring rate affect parasitic loss? I would think this would be noticable if I just dropped in the springs lets say without the cam in question and took a before and after.

8950HO · Aug 12, 2005

crazypete said:
I just finished ordering an FTI cam and it calls for 200 lb seat pressure double springs in leiu of my stock 120 pounders. How much does valvetrain spring rate affect parasitic loss? I would think this would be noticable if I just dropped in the springs lets say without the cam in question and took a before and after.

I`m pretty sure I recall reading on the Crane Cams website a while back that they said stiffer valve springs do not cause any parasitic HP loss,because when the engine is running different valves are in the process of opening and closing and this somehow evens/balances things out resulting in no HP loss.

Check the Crane site.I think the info was somewhere in their valve spring catalog.

vristang · Aug 12, 2005

8950HO said:
I`m pretty sure I recall reading on the Crane Cams website a while back that they said stiffer valve springs do not cause any parasitic HP loss,because when the engine is running different valves are in the process of opening and closing and this somehow evens/balances things out resulting in no HP loss.

Check the Crane site.I think the info was somewhere in their valve spring catalog.

I have not seen the Crane site, but that is contrary to everything I have learned about physics. As the weight force of an object increases, so does the friction. This is how pushing harder on the brakes creates increasing deceleration, and how shifting the weight to the back tires on a launch provides better traction. Again I have not seen the Crane site (Comp Cams all the way!!!!), but that comment does not sound right.

There will be an increase in parasitic losses, but if you choose the right cam, the power gained will far surpass what was lost.

thumper460 · Aug 12, 2005

You NEED springs for two things.. to keep the lifter on the cam lobe and to stop the valve from bouncing on the seat when closed.. Not enough pressure will cause both problems.. Does valve float come to mind?? IF a cam grinder calls for so much pressure.. you NEED that much pressure... and I think STOCK is on hell of less than 120 Lbs installed?? Cool??

Just me.........................

Thumper

QDRHRSE · Aug 12, 2005

Theoretically they should but I don't think its a huge amount of power. In fact I've never even thought about it.

gork1rogues · Aug 12, 2005

You'll lose more hp with a banged up cam and not-so-round lifter rollers.

mr.b · Aug 12, 2005

go to reher morrison's website. They have done dyno testing and talk about have they have never seen a loss of horsepower from stiff valvesprings, but have seen a loss of horsepower from not enough spring (valve float).

vikingpower · Aug 12, 2005

valve springs store energy when compressed(valve opening), and release it when decompressed(valve closing). The only energy (or horsepower in this case) lost during the cycle is in the form of heat from friction at the molecular level within the spring. Isn't physics great?

Car RamRod · Aug 12, 2005

gork1rogues said:
You'll lose more hp with a banged up cam and not-so-round lifter rollers.

That seems like putting extra stress on the cam and lifters for nothing to me.

90mustangGT · Aug 12, 2005

More pressure = more friction. The rest balances itself out due to one valve closing while another one opens.

Of course too little pressure allowing the valves to float will most likley result in less hp. Floating a valve isn't a way to get more durration on a small cam. I guess too much seat pressure would defeat the purpose and only leave more friction.

Grn92LX · Aug 12, 2005

What kinda combo is this with that much spring pressure? Is this a solid roller spring/cam combo?

crazypete · Aug 15, 2005

Sorry for steping away from my own thread. Man just wants to turn some wrenches then life happens, you know?

It's an FTI custom hydraulic roller cam with oooooodles of lift designed to work with 1.7 roller rockers. I asked for a low rpm torquer. The 120 pounders were the AFR 1472 box stock springs. It's gonna be fun trying to compress these things to get them on.

It didnt occur to me the balance of it, I was just thinking of the opening of something with such pressure but didnt occur to me that something is pushing up on the other end of the cam at the same time.

This is my "first cam" so I have a lot of questions running through my mind.

Will stiffer valvesprings eat hp?

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