Big camshafts for RB's

[S15 200sx owner]

What are all you RB__DET/TT guys running in the way of cam's. I was just thinking that the cams (standard) in my R33 Rb25de head are designed for the flow from a 2.5L, well i have this head on a 3.0L bottom end, so surely i could get away with (would need) some bigger cams, as an engine with 20% more swept volume will have a lot more flow and could handle the bigger cams moreso than the 2.5 or 2.6 to a certain degree, even tho i will only be reving this RB30 to 7500 (longer stroke)

 

Surely if i was serious about making good power the standard 2.5 cams will be holding it back.

 

Any recomendations? Lift? Duration? etc.

 

Stony, Matt.

[240Z Turbo]

I had Matt send me a pair of 280/10.25's from HKS. I will have the head modded to accept 11.25's if I choose to upgrade later.

Head is currently at Endyne for some major porting. Shooting for ~325cfm on the intake ports. I purchased the following parts for the head:

 

HKS 280/10.2's

Ferrea Springs

Ferrea Titanium Retainers

Ferrea Seat Locators

Fidanza Cam gears

Endyne Custom Inconel Exhaust Valves

Endyne Custom Stainless Intake Valves

 

Depending on their recommendation I may have them make me a custom set of pistons to optimize combustion efficiency. That would mean I need to sell my current JE forged setup.

 

Don't ask about progress, it will be atleast a 3-4 month before we have information. He has my head and parts along with my spare head that I have given them permission to do with as they require.

[Guest JAMIE T]

325!!!! Holy crap!!!

 

I was thilled to hear this morning, mine did 268 cfm at .400"(10.25mm for the metric guys)!!! Damn, 325!!!?

 

My cams are Blitz 272/10.25mm.

[240Z Turbo]

Jamie,

Those are my desired numbers. He told me the 2JZ heads only flow ~225cfm stock and fully worked they are getting about 318cfm on the intake ports. Now, the Honda B-series heads are another story. He is able to get ~380cfm from the intake ports on those heads. His initial comments were the combustion chambers were deep as compared to the Honda B-series or the 2JZ. This is not optimal for reducing detonation. However, unlike the 2JZ head the intake ports for the RB are straight. We will have a thorough discussion regarding the head Tuesday once his plate is clear. They do very nice work and I have high expectations.

[Guest JAMIE T]

James, While picking up my head today I told my guy about your goals and he said 300 would be no problem at all. He said it would actually be pretty easy. So, I think if some welding and other work is done, 325 might not be all that far fetched. He has also done some serious work on B-series Honda heads. Raising ports, welding the floors etc... I'm handing over my other head to him when that time comes to do that one. I'm going to start a new thread with my numbers.

[cheftrd]

What are all you RB__DET/TT guys running in the way of cam's. I was just thinking that the cams (standard) in my R33 Rb25de head are designed for the flow from a 2.5L' date=' well i have this head on a 3.0L bottom end, so surely i could get away with (would need) some bigger cams, as an engine with 20% more swept volume will have a lot more flow and could handle the bigger cams moreso than the 2.5 or 2.6 to a certain degree, even tho i will only be reving this RB30 to 7500 (longer stroke)

 

Surely if i was serious about making good power the standard 2.5 cams will be holding it back.

 

Any recomendations? Lift? Duration? etc.

 

Stony, Matt.[/quote']

 

With your 3.0, the head is only designed to flow for a 2.5, so you will lose some power on the top end because VE will fall off. A 262 will probably give you back your revs with some extra. Because the 3.0 will probably draw more vacuum signal, you may even be able to run a 272 with no ill effects, other than a slightly elevated idle and a healthy lope. With the 26, vcuum falls off drastically and makes for a hard brake pedal when the AC is run. People talk about "losing bottom end" with larger cams. Yea, if you hit it full throttle at 2000 rpm, the stock cams will probably out pull the big ones... Who does this? It's been my experience that cams through the 300 range accelerate very nicely during traffic light to traffic light, part-throttle acceleration. The engine DOES NOT feel like the slug that people make it out to be. The RB26 is actually quite snappy with a low MOI clutch like the ones from OS. High lift cams in the 290+ range will not drive friendly during low rpm, sustained throttle, though. Severe low rpm reversion in the intake will make the engine want to lope and cause the car to buck through 3000 rpm or so. It becomes an on or off the gas driver. Gas milage will be the victim. It puts a smile on my face

[S15 200sx owner]

thanks Matt, appreciated.