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Help for advice in Crank dampers + Cams + Valvesprings on RB25DET Neo

CefiroA31

By CefiroA31,
in Engines & Forced Induction

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CefiroA31 Apprentice

CefiroA31

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Hi, I am rebuilding a RB25DET Neo (may get an RB26 crank in it) so need advice on crank dampers + cams + valve springs. Purpose of the car for weekend fun in track days/drifts/drags/dyno comps, but also be a reserve to my daily driver, maybe use to get me to work for 1-2 days of a week. I have 3 Holset turbos of identical fitment so can switch between them as needed, smallest turbo should max at 60 lb/min, middle turbo at 80lb/min and biggest turbo at 100lb/min, biggest turbo will likely installed only for dynos/drags. Would like a powerband thats relatively responsive around town while revving up to 8000-8500 rpm. Plan is in the future (2-3 years) it may be rebuilt as a stroker.

What is the limit of new OEM crank damper in either whp or rpm when aftermarket crank damper is needed?

If upgrading to aftermarket crank dampers, what differences in performance/fitment between using RB26 crank dampers like from ATI or Fluidampr compared to Neo crank damper from Ross?

Any camshaft profile recommendations best suited to my purpose? Opinions/experiences on Tomei Type A Poncam 252/9.15 mm, Kelford 264 in/272 ex/9.6 mm, or Camtech 264/9.5 mm or 272/9.7mm?

At what boost and rpm when upgraded valve springs are needed (Per Hypergear Turbo thread, OEM valve springs seems to hold boost of near 30 psi just fine, dont know if  current Hypergear max dyno result of 570rwkw at40 psi is on OEM valve springs or not)?

Thank yous for any advice, cheers.

GTSBoy Grand Master

GTSBoy

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if the proposal is to put a turbo larger than 60lb/min on it at any time then you should budget on replacing the crank damper. It's a reasonable bet that you'll want one for a 26 if you use the 26 crank - but don't trust me on that, as I haven't played with both to know the differences.

If you're going to want to make stupid power than you're looking at at least Camtech or Kelford cams with as much lift as the Neo head can be made to swallow (without shitting shims out! they are shim over bucket, remember), and at least 264° duration. Don't f**k about with Jap cams. If you're putting cams in, just put springs in too - especially if going for the largest workable lift and longer duration. There's no easily defined boost/rev/threshold for this. It just makes sense to do it.

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

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Stock valve springs & Japanese branded valve springs are junk (waits for every American to have a sads) :)

Straight up go Supertech or Performance Springs or Kelford Valve springs in the 80lb flavour.

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CefiroA31 Apprentice

CefiroA31

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29 minutes ago, GTSBoy said:

if the proposal is to put a turbo larger than 60lb/min on it at any time then you should budget on replacing the crank damper. It's a reasonable bet that you'll want one for a 26 if you use the 26 crank - but don't trust me on that, as I haven't played with both to know the differences.

If you're going to want to make stupid power than you're looking at at least Camtech or Kelford cams with as much lift as the Neo head can be made to swallow (without shitting shims out! they are shim over bucket, remember), and at least 264° duration. Don't f**k about with Jap cams. If you're putting cams in, just put springs in too - especially if going for the largest workable lift and longer duration. There's no easily defined boost/rev/threshold for this. It just makes sense to do it.

Thank you for the input, to clarify on first paragraph you mean replacing with new OEM damper or ATI/Fluidampr/Ross damper?

CefiroA31 Apprentice

CefiroA31

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25 minutes ago, Dose Pipe Sutututu said:

Stock valve springs & Japanese branded valve springs are junk (waits for every American to have a sads) :)

Straight up go Supertech or Performance Springs or Kelford Valve springs in the 80lb flavour.

So either stay stock on lower boost/rpm if go bigger get those valve springs, thank you for this.

NZ-GTT Collaborator

NZ-GTT

Posted
Posted
5 hours ago, Dose Pipe Sutututu said:

Stock valve springs & Japanese branded valve springs are junk (waits for every American to have a sads) :)

Straight up go Supertech or Performance Springs or Kelford Valve springs in the 80lb flavour.

I presume the 80lb is seat pressure compared to approximately 20lb stock seat pressure. With such an increase what's the effect on on valve seats, guides etc? 20lb does seem low though.

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted
4 hours ago, NZ-GTT said:

I presume the 80lb is seat pressure compared to approximately 20lb stock seat pressure. With such an increase what's the effect on on valve seats, guides etc? 20lb does seem low though.

I'm going to be honest with you here, no idea 😅

Just I know with SR20 VCT motors, you pull the VCT super quick with stiffer valve springs, in RB25s however there's no talk of grenading VCT units.

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