Valve Spring Pressure

[mike J]

I was thinking of putting new valve springs in my bike over the winter. I was wondering how much seat pressure to use for a street engine? Has anybody played around with this to see if it makes a difference? Mike J

[rosco15]

I run 40 lbs at the installed height on my race motor. I discovered that 50 lbs in my bike was starting to wear the cam right into the rocker arm. If my memory is correct I checked a stock spring something like 26 lbs. I guess the worry is having the valve not close quickly enough and hitting a piston. You can change the installed height seat pressure by shimming up the bottom retainer.

Can you tell it's winter. I've been on her more in the past week than all year.

[mike J]

Thanks Ryan, That's the kind of information I was looking for. I want to up the pressure some but I know somewhere that rocker arm wear will come into play. Mike J

[Big Jay]

A lot has to do with oil also. You can run up to 45 lbs without welded rocker arms if you use Kendell oil. Anything over that should have welded rockers.

Jay

[mike J]

Jay. what weight Kendell would you recommend? Right now I'm running Mobil 1. Mike J

[Big Jay]

We recommend GT40

Jay

[mike J]

Jay, would the motor make more power with Kendell 40w and the springs at 45lbs on the seat or should I go for 40lbs and keep using 0w30 Mobil 1? This bike sees the track quite often but I still want to be able to go for a long street ride with no problems. Mike J

[Craig]

A top end oiler and welded rockers, and you can go very high on spring pressure with no worries about cam wear.

Craig

[duaneage]

Increasing valve spring pressure allows higher RPMs without the springs "floating" and failing to close. Higher spring pressures also allow for larger lifts and more radical cam profiles. The stiffer springs are kinda a consequence of a hot cam since higher valve spring pressures do consume a bit of energy.

If your using a stock cam your likely not to see any difference with stronger springs. The rest of the engine needs to be able to handle higher RPMs to justify the higher redline stronger springs provide. And a racier camshaft also goes along with those modifications.

Considering how much trouble it is to swap them all out I would not bother.