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Discussion Starter #1 (Edited)
I was wondering if anyone had the knowledge to comment on a general guideline to power limit on an RB26 (stock displacement) with varying Camshafts with different Durations and Lift?

Starting with;

Stock Camshafts - Max Power Expectancy ?

And then varying levels of Aftermarket Larger Camshaft;

252deg/9.15mm Lift (Tomei)- ?hp
252/10.05 (Mine's) - hp?
256/8.7mm (HKS)
256/9.1mm (Trust) - hp?
256/9.25mm (Tomei) - ?hp
260/9.15mm (Tomei Poncam) - ?hp
260/10.25mm (Tomei) - hp?
260/10.8mm (Tomei) - hp?
264/8.7mm (HKS)
264/9.1mm (Trust) - hp?
264/9.7mm (JUN)
264/10.0mm (HKS)
270/10.25mm (Tomei) - hp?
272/8.7mm (HKS)
272/9.7mm (JUN)
272/10.2mm (HKS)
272/10.5mm (JUN)
272/11.35mm (JUN)
280/10.2mm (HKS)
280/10.25mm (Tomei) - hp?
280/10.3mm (HKS)
280/10.7mm (HKS)
280/10.8mm (JUN)
280/11.35mm (JUN)
280/11.5mm (Tomei) - hp?
288/10.7mm (HKS)
288/11.0mm (HKS)
288/11.35mm (HKS)
290/11.5mm (Tomei) - hp?
296/11.1mm (HKS)
296/11.3mm (HKS)
304/11.4mm (HKS)
304/11.6mm (HKS)
312/11.6mm (HKS)


Maybe if you have any of these camshafts fitted, would you be able to post what power (flywheel or wheels, please state) your engine produced.

Also, at what level (in terms of lift)

Are head modification needed to fit camshaft?
Are Uprated Valve Springs needed?
Are Uprated Lifters needed?
Are Uprated Retainers needed?

Which Cam for;?
Street Tunes on Stock Turbos with Upp'd Boost
HKS GT-SS or 2510
HKS 2530 or similar on 1.5bar
or larger?


I need to start looking at what camshaft will fit my needs and wanted to do some homework but also compile the information in one place for others to refer to.

I want 550-500 whp with HKS 2530's at max boost on stock displacement (with all other modification to support), I want to circuit race the car but also drag race it (would like low 11's).

The 260/9.15mm Poncam seems like a nice popular camshaft, however am concerned with 9.15mm lift I will not hit my target hp. ???
 

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Discussion Starter #2
>9.15mm Lift = Head Modification.
??? True?
Modification as in grinding of "bucket" area? Can anyone go into more detail?
 

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You can run 9.15 without mods.

The max duration of camshaft for a 6 cylinder with emissions in mind is 240deg (the std duration). Hence any longer duration, overlap starts becoming an issue and mpg goes right out the window.
 

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I am going to be buying a but load of jun parts and I was interested on peoples oppinions on the titanium retainers with the jun 2r kit.

Is there any reason to spend the extra 30k yen for titanium retainers or are the regular jun ones good?

Is there any reason to change from stock?
 

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Discussion Starter #5
As far as I know. as long as the titanium grade of material is high (or durable) enough, titanium retainers from the aftermarket manufacturers will work level and for sustained period of time, where the concern was the wear rate.?

R32combat, cheers for informing about the economy/mpg relation to overlap/duration, I wasn't aware it was so related/proportional.

Stock Camshafts then are 240deg/8.25mm lift?


Do RB Motors respond in the same way as a general increase in output across the range with " greater lift as possible : shorter duration as possible " ? is that a good general rule of thumb?


Will HKS 2530's run out of steam before a 9.15mm lift cam will raise efficiency issues? In other words, would the money be wasted on modifying the head for c.10.5mm lift with this turbo setup?

It's a big difference (in terms of cost and time) between slapping in a set of Poncam's (260-9.15) and going to 10.Xmm lift Pro Cams + Headwork + Springs + Lifters + Retainers.

I'd hate to get the car on a dyno for mapping .. everything else being engineered enough (the turbo's, the fuel, the correct egt) ....with the wrong choice of camshaft and not hitting the 500whp goal I'd love.
 

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Ti retainers are a total waste of money. You will never be able to measure the difference unless you are revving 10K+ rpm.

I run JUN 272 10.5 cams with the STD springs and retainers.

Higher lift is usually related to cam duration due to the ramp angle. You can't have 11.5 lift on a 240deg cam because the ramp angle would be too high.

264 cams will easily produce [email protected]

The smaller the lift, the harder you need to blow through the hole, but 2530 will work admirably.
 

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so 2530s mate up well to Poncams/other mild 260-ish cams? How much then are you holding them back with stock cams?
 

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Discussion Starter #9
Q. When running camshafts with more than 9.15mm lift,.. physical modification is only needed to the lifter buckets? (Material grinded away from the top of the bucket? the bottom of the bucket? where? please can someone explain?)

R32Combat, what did you have to do (physical modification and parts replacement) to fit 272 / 10.5mm camshafts into your cylinder head with stock valve springs please mate?


PS. I'm not going to do the camshaft fitting myself, I will send to RBMotorsport. I just want to research what is done at each level and why to fit larger cams into the RB26 Head.
 

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Q. When running camshafts with more than 9.15mm lift,.. physical modification is only needed to the lifter buckets? (Material grinded away from the top of the bucket? the bottom of the bucket? where? please can someone explain?)
No material is taken from the actual bucket , only a small section of the bore that the bucket travels in .
 

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It's the sides of the pocket that the lobe sweeps through that needs machining.

Buckets are only changed when going to very high lift cams that need a smaller base circle on the lobe to achieve the lift.

From memory the standard and up to around 10.5mm lift are on 32mm base circle and beyond that 30mm base circle with corresponding thicker buckets.
 

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^^^^ Ditto

I used 3.8-4.2mm thick shims and slightly modded retainers to accept the larger diameter. The base circle is smaller on my cams. JUNAUTO display the base circle on there cams so you know roughly how this the shims will need to be.
 

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Hey Loz. Keep it nice and simple on the head. All the lads I no at Mascrat running 500whp are either running the Tomei Pon Cams 260 9.15, HKS 272 8.7 and 1 guy is running the Jun 272 (not sure on lift).

You dont need to do anythink to the head expect for cams, metal gasket and a service. Im also fitting new bronze valve guides to be sure on reliability.

You can go up to 10mm lift befor you need serious head work and the Tomei's @ 9.15mm are the closest i've seen and thats what i'll be fitting.
Also i've been told it may be wise to fit some kind of oil drain on the back of the head! But will have to double check on that.

Loz, have a look at some of the threads on Octane Junkies. Were starting to talk technical about the engine rebuilds. Also i'll be buying alot of bits in the new year so maybe we could sort somethink out about getting hold of them cheaper.

Baz
 

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I have bought HKS 272 / 8.7 lift, running them on stock springs/retainers ..

Do I need different shims or these step1 cams are fine and close to stock cams shims wise ?
 

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all other things being equal, what's the difference between HKS 272/8.7 and Tomei 260/9.15? Greater lift on one, longer duration on the other - what does this translate to in terms of engine response?
 

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all other things being equal, what's the difference between HKS 272/8.7 and Tomei 260/9.15? Greater lift on one, longer duration on the other - what does this translate to in terms of engine response?
Anyone got an answer to this? More torque on 272?
 

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I run Tomei Pon cams 260deg with jun springs and standard retainers and car runs around 750hp (706.8hp but spinning the wheels)
 

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Anyone got an answer to this? More torque on 272?
Increased duration cams require higher revs to deliver their maximum power.

There is also the ramp angle on the cam to consider, greater angle means higher loads to turn the cam.

Higher lift cams will deliver more power at a slightly higher RPM compared to their lower lift family assuming the same ramp angle.

Titanium buckets reduce the mass of the valve that has to be opened, so can be opened faster using an increased ramp angle.

Cams are designed so that they can be used with a specific mass of valve, spring, retainers etc at up to a safe working RPM.

Pretty hard to nail down what you want.

Tomei manufacture and sell great cams with matching valves and springs with titanium followers for the higher lift.

Tomei manufacture cams for a number of the Japanese suppliers, great quality and hard to beat.
 
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