Cam Advice For 25/30..

[bubba]

OK guys, things are progessing quite steadily and am wondering what to do with my cams (am not forking out for huge cams and a solid lifter conversion). Stumbled across this cam info again and am trying to figure out whether to stick with the 25DE cams or whether a combination of 20DE/20DET/25DE cams would be better..

RB20DET

Ex - 240 duration, 7.8 lift, opens 60 BBDC, closes TDC, LCA 120

In - 240 duration, 7.8 lift, opens 5 BTDC, closes 55 ABDC, LCA 115

overlap = 5, LSA = 117.5

RB20DE

Ex - 240 duration, 7.8 lift, opens 57 BBDC, closes 3ATDC, LCA 117

In - 232 duration, 7.3 lift, opens 5 BTDC, closes 47 ABDC, LCA 111

overlap = 8, LSA = 114

(R32) RB25DE

Ex - 232 duration, 7.3 lift, opens 54 BBDC, closes 2 BTDC, LCA 118

In - 240 duration, 7.8 lift, opens 9 BTDC, closes 51 ABDC, LCA 111

overlap = 7, LSA = 114.5

Relevant specs of the engine are:

RB25/30 (R32 RB25DE head)

Stock RB25DE (R32) cams

GT35R 0.82 exh housing

6boost manifold

50mm gate

Rev limit will be 7500rpm and looking at somewhere around 500rwhp. Can someone with a good working knowledge of cams in RB engines please help!

[Adriano]

Have you considered a pair of reground rb26 cams like cubes has?

[psi]

I'm in the same boat!

I have been considering stock RB25DE cams, but.. have no real clues to see if it will help me gain where I want it to gain.

My current plan is to build the engine and get it tuned.. Then go from there.

But that is not very helpful, and is a pain in the butt if it doesn't do what I'm wanting it to do!

[craked]

i can give you a custom grind number for cam tech cams if you want killer cams not to be pm me for cam profile

[bubba]

Have just spent an extra 4k that I wasn't orginally planning to so I'd rather not spend $_$ on new cams unless I can really, really justify it..

Just for some comparison, these cams in this head made 490rwhp @ 22psi with a pair of 2540's.. I've had a mechanical engineer tell me to use the 20DET cams over the 25DE.. not sure on the justification though.

Craked, PM sent.

[psi]

craked, pm sent

[mr_rbman]

2nd hand gtr cams = $80

tighe cam regrind = $220

extra power = 28rwkws @ same boost.

Edited May 3, 2009 by mr_rbman

[TiTAN]

to expand on this thread, does anyone local do cams that work WITH VCT for the R33 head?

[bubba]

2nd hand gtr cams = $80

tighe cam regrind = $220

extra power = 28rwkws @ same boost.

Interesting..

[mr_rbman]

Interesting..

definitely one of the best mods i did.

[psi]

now that is my kind of bang for buck!

but, does anybody do that kind of improvement for a VVT cam?

thanks for the tip!

[bubba]

definitely one of the best mods i did.

Care to share your cam and engine specs? PM me if you want

[Bliksem]

to expand on this thread, does anyone local do cams that work WITH VCT for the R33 head?

Also interested to know this, so far I only know of Colt Cams based in Canada Link A local alternative would be great.

Edited May 6, 2009 by MintR33

[mr_rbman]

Care to share your cam and engine specs? PM me if you want

i got no secrets!

stock rebuilt rb30 with rb25 non vvt head from r32

gtr injectors

power fc

xr6 35/40

reground gtr cams

[bubba]

i got no secrets!

stock rebuilt rb30 with rb25 non vvt head from r32

gtr injectors

power fc

xr6 35/40

reground gtr cams

Nice!

That turbo has a 1.06 rear yeah? what power are you making and at what boost (and when do you see it?)?

Obviously it drives pretty nice going on how happy you were with the cams..

[mr_rbman]

ye it has the 1.06 rear and ideally i would've liked the smaller rear but this turbo popped up at the right price.

it currently makes 251@12psi, only reason i'm not running more boost is i dont have a boost controller and i can't warrant spending more money on a car i never drive. makes that boost by about 4000rpm but because its so torquey off boost it doesn't phase me.

cheers!

[Turbz RB-25]

256 pon cam inlet 264 HKS Exhaust with adjustable cam gears

[psi]

how would a 260 intake and 272 exhaust cam work on the RB30 with a GT3040?

[Dale FZ1]

Got a couple of variables there you'd need to work on.

What turbine A/R?

What spec are the rods and rod bolts?

The cam specs suggest pushing the effective rev range upwards - ie. moving the torque curve to the right. Turbine housing choice will move your torque curve around as well.

Some who've used the GT3040 suggest it's great/useable/driveable, although the compressor flow is likely to outstrip the turbine flow capabilities. For the higher rpm and power capacity the cam specs suggest, perhaps chase a GT3582, and make sure the bottom end is built to withstand 8000rpm? I tend to think for some applications the XR6-T version is quite a decent match for a RB30DET. Possibly a bit of a soft delivery down lower, but the relative lack of turbine backpressure allows it to hold decent torque as revs rise. Be interesting to see a dyno sheet for mr rbman.

Otherwise recommend putting the specs through a Cam Doctor review and see what the predicted results are

Edited May 12, 2009 by Dale FZ1

[R31Nismoid]

^^ GT30 is comp flow limited not turbine

hence a GT35 has a large comp wheel and relatively the same rear (from my understanding) and hence the 100hp difference in rating