Stock Valve Train Rev Limit

[bigcarl]

hi every body just need some advice from people that know. iam running gt3040 powered rebuilt rb25 with gtr rods , wiseco forged pistons , tomei step 1 poncams and ported head. im running stock hydraulic lifters and valve springs. im wanting to rev the motor past 7000rpm to take advantage of the extra top end this gt3040 turbo gives me. whats a safe red line to have? thanks carl.

[R31Nismoid]

Mine was set to 8000rpm.

That was knowing full well it woould see the drag strip, and it did a few times

Stock head aswell, not even cam'd

So i cant see why you cant do the same if its still making power.

You have the rods & better bolts, so DO IT

[bigcarl]

thanks for the advice r31 nismoid. im hoping to take her to the drag strip also. and the budget doesnt allow for solid lifter and cam upgrade.

[Roy]

Surely the boost you are looking to run will also play a part as the revs go up, and the valve springs and lifters ability to handle the cylinder pressures/temperatures and revs

[R31Nismoid]

well that was while i was using 24psi and race fuel... ran the car like that for 4-5 months both on and off the street

Head is still perfect as its been off recently

[r33_racer]

Does anyone know for sure or has had experience when valve float has started to occur in the 25's with whatever modifications they have had done?

Im curious to know if it happens often or not at all, i have yet to see anyone complain about 25det and valve float. Ive heard its a problem in neo25's cause their springs are weaker then the previous models, is that true as well if anyone knows?

[R31Nismoid]

everything has its limits, thats quite simple.

but 25det heads are quite good.

From what ive performed, and it wasnt just a dyno run it was a few hard months that broke many things, but not the head

[R31Nismoid]

everything has its limits, thats quite simple.

but 25det heads are quite good.

From what ive performed, and it wasnt just a dyno run it was a few hard months that broke many things, but not the head

[turbo87]

My car has very similar modifications to yours including same turbo, on 20psi the valves started to float around 7500rpm, by keeping the revs down around 7000rpm we made 360rwkw on 24psi

[r33_racer]

Well thats good to hear. Just that were upgrading the springs to some stronger Isky ones for the 25/30 just to make sure..we will be running around 22-25psi outta the 3540. Just wanted to check incase anyone had run into such problems before.

Ok so someone has run into problems...well our redline on the 25/30 will be 7k due to standard harmonic dampner, so with the stronger springs we should be good.

What turbo may i ask were you two running R31Nismoid/turbo87?

Edited April 24, 2006 by r33_racer

[turbo87]

I'm running a gt3540 with 0.82 exhaust, gets slight compressor surge on 24psi as well.

[R31Nismoid]

GT30 600hp, 24psi, race fuel for my ~360rwkw.

Like i said, my head was in A-1 condition when the motor was done.

If you motor is tired, you will probably get some problems as wear sets in

[N I B]

Ive run a few to 8500rpm long term but never over 25psi,Maybe ive been lucky but even the shop drifter has not given trouble.

Ive seen one RB25 spring fail and that was only a loss of pressure.

[gtst25]

I set mine at 8000rpm but change at 7500 - absolutely no problems and it sounds great up there!

[bigcarl]

gts 25 is that with stock cams? what power at what psi?

[gtst25]

Yep stock cams. 255 rwkw. Gets the next gear nicely upshifting @ 7500. Boost peaks @ about 19 or 20 psi then tapers off.

Cheers

[BHDave]

I also ran into valve float at about 21psi. It started around 4k according to my tuner.

That was on an HKS t300s turboed stock cam'ed s1 rb25 making about 240rwkw up top. I've got my rev limit pegged at 7300 more due to worries about the stock rods than the valve train.

[Busky2k]

You might be able to get away with 7500-8000rpm with stock cams, but throw in a pair of HKS/Tomei or whatever uprated cams and you won't be able to push it as far without trouble! (on stock springs of course)

[bigcarl]

im running tomei poncams step 1 252 degrees duration at stock 8.5mm lift. now wouldnt running these cams with stock lift enable me to run similar rev limit to if i had the stock cams still installed??? if im going to run 22psi on hi boost do i need to restrict revs to 7000rpm or can i go to 7300rpm ? without valve float any ideas people???

[gtst25]

If installing pon cams I'd recommend upgrading the valve springs to gtr items. With stock lift I'd say you should be able to hit 7500 but you'l certainly find out. Didn't you have a gt 30 with nissan exhaust housing before or am I getting mixed up?

Cheers