Rb25 Standard Valve Spring Capability

[turbo87]

I have been told that the rb25 standard valve springs will begin allowing the valves to leak at around 20psi or 400rwhp. Wondering if anyone has any experience with this?

Thanks

[BezerkR32]

Yes last two r33 ive setup experienced valve float at around 20psi out of gt 35/40, which were making 285kw or 390hp at tyres.

I have been told that the rb25 standard valve springs will begin allowing the valves to leak at around 20psi or 400rwhp. Wondering if anyone has any experience with this?

Thanks

[SirRacer]

they are pretty average and id suggest replacing them while you have the engine in bits

[Luke 34GTT]

I might be confused with what you mean, but if your talking about the valve springs in your cylinder head, valve springs dont have anything to do with hp ratings etc. There issue is RPM. It Shouldnt matter if you run 40psi, as long as you dont go to far over the standard rev limit and the valves and seats in the head are in good condition the valve springs should be fine.

Edited March 27, 2006 by Luke 34GTT

[sky30]

I might be confused with what you mean, but if your talking about the valve springs in your cylinder head, valve springs dont have anything to do with hp ratings etc. There issue is RPM. It Shouldnt matter if you run 40psi, as long as you dont go to far over the standard rev limit and the valves and seats in the head are in good condition the valve springs should be fine.

The more boost you run the more pressure there is in the cylinder to push the valves open.

[Sydneykid]

Boost in the inlet system slows down the closing of the inlet valves, as the valve spring is trying to close them against the boost pressure. The closing valve no longer follows the camshaft profile (ie; valve float). Around 19 psi is a reasonable rule of thumb limit we work to.

You can increase this slightly by shimming the standard valve springs, but there is not a lot of room before coil bind becomes an issue if you are using higher than standard lift cams. So it should be done very carefully.

Hope that was of some help

cheers