Vavle spring and such ; need information please!

[cobrAA]

Hello,

After reading GTR-Dad's post yesterday, he said he would like to change the valve spring so he could rev up to 9000. I know about this fix before but I would like to know really how it works.

Do you simply buy some BC spring valve and you call it a day or you need machining? because I can,t see any valve spring keeping the oem spec and seems to offer a lift and if it does then you know it won't fit anymore in the head. do you need to buy valve after this?

I know very little with rb26 head to be honest lol!

Thanks!

[Daryl @ RightDrive]

Are you using factory camshafts? If so there is no need to change the valve springs.
Usually they are used with higher lift cams.
As for revving up to 9000rpm, you should be sure that you have an aftermarket oil pump (not N1!) and other supporting mods to handle that as well.

[Bruizer]

Are you using factory camshafts? If so there is no need to change the valve springs.
Usually they are used with higher lift cams.
As for revving up to 9000rpm, you should be sure that you have an aftermarket oil pump (not N1!) and other supporting mods to handle that as well.

Oil pump drive issue fixed, fully balanced rotating assembly, so on. I went nuts on my engine but won't be going past 8000rpm where things must be so perfect. My -5 turbos start making more heat then power after that anyways.

Why do you want to go to 9000rpm other than wanting the bragging rights?

[Skym]

From what I understand, higher rpm increases inertial load on bottomend that can snap conrods like twigs. It's something like 3.5 tons every 1000rpm (I would think it depends on piston size / weight of piston as to how much weight there is on top of conrods). It's safer and less harmful to lower rpm where peak hp is created (around 6000rpm) and use boost level to create the hp. This is how some import dragracing engines are tuned.

If reving higher than stock revlimit, titanium conrods are best but not cheap. Not even cheap H beams can survive a big increase in rpm above stock rev limit and snap like twigs.

Valve springs are rated to a set revlimit and lift -

http://www.tomei-p.co.jp/_2003web-ca...lvespring.html

I was advised to change valve springs on my cars RB20DET engine since engine produces peak hp at around 7500rpm (stock revlimiter and max rpm for stock valve springs). Max lift of stock valve springs is around 8.5mm with Tomei Poncams (stock cam lift is 7.8mm). Also changing valve springs sets head up for more aggressive cams later on.

[Marus92]

I'd personally change valve springs if I'd be going over the RPM design limit because of valve float. Even if the cams have the same lift and/or duration, there is a possibility that the configuration of the coil and the material type can't exert enough energy (low spring rate) to lift the valve before inteference at a higher RPM. Add to the fact that those springs have been cycled for a long time (spring rate loss) and I think it would be on the safe side to go step up in stiffness.

That's from a totally theoretical and technical standpoint though. If the guys that have more RB26 experience tell you it's safe, take their word over mine.

[frankiman]

Why do you want to go to 9000rpm other than wanting the bragging rights?

this^^

[Skym]

I was looking at the cams in my engine not long ago and noticed what looked like little black scoring marks on base circle of cams on both sides. The V part of lobe was clean. Makes me suspect valve float at higher rpm and could be what my mate saw. I guess that's why he mentioned to upgrade the valve springs.

[GTR-Dad]

Why do you want to go to 9000rpm other than wanting the bragging rights?

Context is everything. My upgrades are for reliability and forgiveness if/when revs exceed my best intentions. I'll prbly tune to 8k or so and be happy that my valvetrain and everything else is up for the job plus a healthy margin. I expect my peak torque rpm to move up this season as well so peak power may well be between 8k-9k rpm. No need to go there however, just because you can.

OP - you need springs to match your lift and max rpm. OEM springs can approach coil bind with high lift cams. As someone mentioned, floating valves is bad. More spring force elevates the 'float' rpm, but also increases normal force on the camshaft thereby increasing tangential load for the same friction coefficient. (Parasitic drag and wear both move in the undesirable direction)

When calculating inertial load resulting from increased rpm's, recall that F=ma and a is proportional to velocity². Doubling your rpm increases inertial load by a factor of 4.

Hope this clarifies a few things.

Dan

[DJ]

Might want to check the srping tension and see if they're to spec.I'm not planning on reving more than 7800-8000rpm but with a build bottom end I didnt want some guide cracking on me so I sent the head to a shop to get the guides and seals replaced but the builder told me with the poncams I might aswell upgrade my springs now just to be safe.After all new guides+seals+seats+springs+labour...Headwork is expensive my friend...

[Bruizer]

Well said Dan, same reason I went be tomei B springs and built to turn to 10k by never will.