Advice On Camshaft Choice

[Jap_Muscle]

Hey guys,

Currently running a rb26/30 combo in a rwd r34 gtt. currently makes 308rwkw on 20psi with a gt35r/82 and OEM rb26 cams. my aim is to crack the 400kw mark.

Some have suggested my setup suffering from valvefloat and some have said i need bigger cams. Nengun have listed some Procam + Adj Pulleys however id like to know what cams will drop straight in, and what cams will need work to fit?

Also a few questions

- I understand Pro cams need new valve springs regardless of if they need it or not?

- And what are the differences between Pro-cams and Pon-cams.

Basically im not very informed when it comes to what makes a good cam choice, so any help much appreciated. the car is a 90% weekend street car with the occasional drag strip night.

cheers

[zebra]

you really should be making 350+ with that combo at 20psi

Do you have a dyno print out?

[Jap_Muscle]

unfortunately not with me at this stage, but i should have it up within the hour.

any thoughts on wat could be happening?

[NYTSKY]

400rwkw with a 35R is harder to reach than you think.

Im making 390rwkw with E85 and 256/264 cams at 25psi.

My dump pipe and cooler are being the restriction. Im expecting a tad over 400 when these issues are seen to.

[zebra]

I'd check over everything, make sure cam timing is spot on, no leaks etc.

Unless the head has seen 11ty billion ks it really shouldn't valve bounce/float

[Jap_Muscle]

400rwkw with a 35R is harder to reach than you think.

Im making 390rwkw with E85 and 256/264 cams at 25psi.

My dump pipe and cooler are being the restriction. Im expecting a tad over 400 when these issues are seen to.

i dont think you should be resorting to e85 to make 400kw. im almost certain it can be done on pump fuel. your cam choice might be a tad on the small side though. the spec sheets ive seen with simliar setups are mostly all running 270s.

any porting and polishing?

I'd check over everything, make sure cam timing is spot on, no leaks etc.

Unless the head has seen 11ty billion ks it really shouldn't valve bounce/float

ill have to clarify everything with my tuner in terms of timing ect.

as for float, i am very skeptic its the issue. and reluctant to spent $500 on a "maybe"

[N1GTR]

Procams (as Tomei's website says, why does no one search anymore) require new buckets and clearancing, poncams are drop in and require no clearancing or bucket changes.

Edit; this probably isn't valve float given how far stock springs get pushed with no floating issues.

I'd be going for 260 in and ex with 10.8mm, but your going to spend a fair bit then. If you don't want to spend the 500 on springs, maybe you shouldn't be changing cams a this will cost more than 500. Cams, 850 or so, buckets, 450 or so, labour, say 400 or so but then there's clearancing aswel

[N1GTR]

Look at restrictive exhaust, piping, intercooler, plenum and manifold etc

[R31Nismoid]

Currently running a rb26/30 combo in a rwd r34 gtt. currently makes 308rwkw on 20psi with a gt35r/82 and OEM rb26 cams. my aim is to crack the 400kw mark.

Some have suggested my setup suffering from valvefloat and some have said i need bigger cams. Nengun have listed some Procam + Adj Pulleys however id like to know what cams will drop straight in, and what cams will need work to fit?

So in 6 months you've added in more boost... and lost power

as i mentioned before the car is currently sitting at 330kw on 16psi which is a great effort i guess, but the turbo is no where near its efficiency range.

Last time we TOLD you that you don't need CAMS (Guilt-Toy has made ~370rwkw factory RB head) as you had a mechanical issue somewhere

http://www.skylinesaustralia.com/forums/Re...5r-t287217.html

It would certainly seem that now you 100% have a problem as you've increased boost and lost power...

Do you now understand that you have to spend some money getting things checked out?

Swapping the CAMS will not magically fix your issues.

[rob82]

What inlet manifold?

[R31Nismoid]

RB26 - It's all in the thread i linked from last year

[Jap_Muscle]

this probably isn't valve float given how far stock springs get pushed with no floating issues.

I'd be going for 260 in and ex with 10.8mm, but your going to spend a fair bit then. If you don't want to spend the 500 on springs, maybe you shouldn't be changing cams a this will cost more than 500. Cams, 850 or so, buckets, 450 or so, labour, say 400 or so but then there's clearancing aswel

im fine with spending the money, just not on something that may or may not fix the issue.

Look at restrictive exhaust, piping, intercooler, plenum and manifold etc

i dont think the exhaust is restricive as im running a 3.5" straight pipe drag exhaust and is connected via V-bands including the dump. i also questioned the plenum im running (standard rb26 one) but i understand they have no issues flowing 400kw. and the manifold is a 6boost item which made 330kw before. but why less now?

So in 6 months you've added in more boost... and lost power

Last time we TOLD you that you don't need CAMS (Guilt-Toy has made ~370rwkw factory RB head) as you had a mechanical issue somewhere

http://www.skylinesaustralia.com/forums/Re...5r-t287217.html

It would certainly seem that now you 100% have a problem as you've increased boost and lost power...

Do you now understand that you have to spend some money getting things checked out?

Swapping the CAMS will not magically fix your issues.

the reason why im asking about cams is that i know ill need cams to make 400kw. as far as the issue atm of making low power, im stumped and i know cams isnt the solution. but im trying to get things done in one go once i have the answer.

What inlet manifold?

im using a standard r33 gtr plenum and tb with a 6boost exh manifold.

i just dont know why its making so lil power. would you guys need a dyno sheet to get some answers?

Edited April 22, 2010 by Jap_Muscle

[Jap_Muscle]

do you guys think its a tuning issue?

im currently running a r33 gtr PFC which is connected to the rb26, however im also running the cars original ABS and AC settings via the OEM r34 GTT ecu. basiclly only using inputs for the abs and ac where needed. everything else is pretty much managed by the gtr PFC which is also mafless.

do you recon there may be some issues caused with tuning here? theoretically i dont think so because the only things managed by the OEM ECU is the ABS and AC.

[R31Nismoid]

IMO you really need to workout what the issues are BEFORE you go changing parts around.

As opposed to changing this/that & the other without really knowing if it's even going to do anything.

You haven't actually tried to drop the exhaust, assuming something is "OK" is never a good thing.

Also same for any other issues, you've ruled nothing out.

You might find the issue, fix it and suddenly you are making 380rwkw which is pretty much your aim solved.

[Jap_Muscle]

hey guys heres my graph as promised (a bit late sorry)

any comments?

Edited April 28, 2010 by Jap_Muscle

[GTScotT]

typical 35r curve...

as stated above, it sounds like there is a flow problem somewhere... particularly that you have added more boost only to have lost power.

as reference, I once had an issue with the ID of a cat. The inner diameter of the cat was a total 3mm smaller than the frontpipe and no matter how much boost was wound into it, there was no hope of it making anywhere near its potential power. Once that issue was resolved (no longer a lip in the exhaust) the car went on to make above and beyond its projected output.

that sort of thing could be in your cooler pipping, your cooler, your exhaust, your suction pipe etc

if your serious about getting help where your tuner really should prevail, try and give us as much description as humanly possible about your setup. its every detail would be advisable.

[R31Nismoid]

Doesn't help much at all.

Add to the fact the settings are not listed down the bottom either (who knows what/how that figure is being attained etc)

[T04GTR]

these videos may make you decide to get better valve springs.

v8 nascar with "top shelf" valve gear..

[Swiper the Fox]

std stroke and bore RB26, stock springs, 9.15mm poncams, 34psi making 467kw at the tyres...HKS 2530's.

no need for anything bigger than this on a low revving RB30. Throw some springs at it if you feel the need though.

i don't think that camshafts or springs (unless they are faulty) are holding you as far back as you are now.

[rob82]

What intercooler? Have you tryed running it with the exh off and try putting the dyno into shootout mode? Is there any timing scatter up top? Have you done a comp and leak down test? I'm sure I can keep taking a stab in the dark for the next 3 days but what you needto do is get it to a good tuner.