R34 Rb25 Neo Valvesprings And Hardware?

[BlackBox]

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?

[BlackBox]

Bunping

[BlackBox]

Bunping

[BlackBox]

Bumping

[BlackBox]

Bumping

[lcxu105]

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]

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 February 14, 2015 by AngryRB

[Aggroman]

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.

[lcxu105]

Why risk a new engine on a chance. Rather do it right first time.

[devilsknife]

hey guys im building my engine Rb25/30det but im using the whole ferrea top end kit bit pricey but we used it in our top alcohol drag car hasn't missed a beat 6 secs all day

[AngryRB]

how do the springs know what psi is being given?

[RRob]

I fitted a set of Performance springs and retainers to my 2.6 Neo. Handled near on 2 bar fine, although the car has only done about 4 k's in 2 years.

[KiwiRS4T]

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

[Ben C34]

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]

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]

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]

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.

[AngryRB]

Seems im wrong here.. , this spring issue was never raised by my tuner and a lot of others seem to bolt stock neo heads onto RB30's seemingly without issues?

[GTSBoy]

Is it because 3L don't rev!?!?

[GTSBoy]

Note, I didn't use italics, but I'm hoping you will all get it anyway.