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R34 Rb25 Neo Valvesprings And Hardware?

BlackBox

By BlackBox,
in Engines & Forced Induction

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BlackBox Rising Star

BlackBox

Posted
Posted

Hi,

i will be fitting a set of tomei type B poncams (260deg 9.15mm) to my rb25det neo soon, but im having a hard time finding suitable valve springs. Can anybody tell me if the standard valve springs are single or duel springs? will i need to change valve spring guides if i go from single to duel or vise versa?

Also what is the general consensus on reusing retainers, collets and cam hold down bolts?

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Dose Pipe Sutututu
Dose Pipe Sutututu

lunacy to toss the VCT, each to their own

Mick_o
Mick_o

DUMB.....

Piggaz
Piggaz

PSI is VERY relevant.I can't see how power can make any difference seeing that both valves are shut when it goes "bang". Boost pushing against the intake valve is a big contributing factor in float.

  • 8 months later...
lcxu105 Proficient

lcxu105

Posted
Posted

In the same boat as you. Have been told that the neo head can handle 22psi on pump fuel and 25 26 on e85. But if wanting to run more than 22psi I need to upgrade the spings. Have been told by a few people to stay away from profamance spings and go for supertech spings. Been having problems finding them tho.

AngryRB Grand Master

AngryRB

Posted
Posted (edited)

why not just see how it goes on the dyno? pretty sure a lot of people have had no issues without even opening the motor..

worst case scenario is they start to valve bounce and you have to change them then a touch up tune??????

Edited by AngryRB
Aggroman Grand Master

Aggroman

Posted
Posted

with the tomei type b's you run the risk of spitting a shim with standard springs. they wont float or do anything bad its just one of the things that CAN happen.

Tomei do a matching valve spring but Jap springs are rubbish.

Ring places like supertech about a spring to suit 25neo which is a shim over bucket (not shim under bucket like rb26) single spring with something like 64 pound seat pressure (least i think its 64 pound but that was a bulldog spring for some serious ramp rate cams so might be a bit overkill for you.

Ben C34 Grand Master

Ben C34

Posted
Posted

how do the springs know what psi is being given?

The pressure applied by boost to the back of the inlet valve is how they know. The more boost the more pressure trying to open the valve.

So running 20 psi adds 20 psi of opposing force to the spring being able to close the inlet valve.

Ben C34 Grand Master

Ben C34

Posted
Posted

As Mark says PSI is irrelevant - revs, power and cam profile will determine the need for new springs.

Just to add to my previous post, power makes no difference to valve spring requirements.

How does the valve know how much power its making?

Revs, cam profile and boost are basically the factors.

Notice how engines valve float but when boost is reduced can still rev cleanly to redline? The valve opens and shuts just the same when at max revs regardless of power output, the difference is how much boost acting against the inlet valve closing.

BlackBox Rising Star

BlackBox

Posted
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Posted

I ended up getting 'performance' springs, haven't installed them yet tho.. Isn't a big name brand but haven't heard anything bad about them plus aussie made so should be sufficient.

why not just see how it goes on the dyno? pretty sure a lot of people have had no issues without even opening the motor..

worst case scenario is they start to valve bounce and you have to change them then a touch up tune??????

Because I have to travel ~ 2000km return to a tuner, why not do it right the first time

Piggaz Grand Master

Piggaz

Posted
Posted

As Mark says PSI is irrelevant - revs, power and cam profile will determine the need for new springs.

PSI is VERY relevant.

I can't see how power can make any difference seeing that both valves are shut when it goes "bang".

Boost pushing against the intake valve is a big contributing factor in float.

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