Tomei Procams For Rb25det

[r33cruiser]

Hey guys. Im in the process of finding a set of tomei PROCAMS.

My mechanic and I have been talking at length about choosing the correct sized cam for my application, and Im sure he is probably reading this too

We have narrowed it down to the 260 range. I have been advised to go 260-9.25mm lift. The reason for this, while my engine was being built we had another engine being built to basically the same specs as mine, however this one had 270-10.25mm cams. This engine had suffered valve spring issues (springs unable to cope with the lift- thats all i can recall), and recently after its final tune it broke one of its springs. Luckily no major damage was done to the engine. So if i play it safe and go the 9.25's we shouldn't run into this problem.

So, my question; Can i safely run the 260 10.25mm lift cams? Can anyone vouch for the tomei type B 10.25mm springs as being bulletproof?

Or Should I just make it easy for myself, play it safe and go the 9.25mm lift cams to give me a safety margin?

Engine is powered by a gt3582, and I don't have a specific ''Purpose'' for the car, its not a dedicated drift bitch, track whore etc. The head is going solid, ported etc etc.

Would like to make 550rwhp, anything more would be a bonus, but I doubt the turbo will make it further than that.

Edited September 12, 2009 by r33cruiser

[Tomei_Powered]

Im running PROCAMS 260 10.25lift with no problem so far.

You need to change to the Tomei type B valve springs and solid lifter and also with the right thickness of shims.

Im making 441whp (Dyno Dynamics) @ 1.5bar w/GT35R w/TO4R compressor without adjusting the cam gears.

You can safe rev till 9k rpm but make sure you have the supporting internals and oil pump for it.

I will be posting my built soon.

Cheers!

[shanef]

To achieve 550rwhp on that turbo setup, you are going to have to have a really good quality head. i.e oversize valves, a port/polish/chamber job that will actually work and valvetrain gear to support it. Its also going to need a pretty spot on tune aswell with upwards of 25psi+.

I'd go the 260 10.25 cams and a good qualty set of springs (supertech are a really good quality spring that are reasonably priced), source them from the states.

[R31Nismoid]

To achieve 550rwhp on that turbo setup, you are going to have to have a really good quality head. i.e oversize valves, a port/polish/chamber job that will actually work and valvetrain gear to support it. Its also going to need a pretty spot on tune aswell with upwards of 25psi+.

I'd go the 260 10.25 cams and a good qualty set of springs (supertech are a really good quality spring that are reasonably priced), source them from the states.

Yet Guilt-Toy made 370rwkw with a stock head and a GT35

Admittedly it was 3ltr, but that's not the be all and end all.

I've also made 370rwkw through a relatively stock head (minor porting touch up, that's it. Stock everything else) as well with a GT30 on juice...

I think there is a lot to be said for a stock RB25 head/cams, you certainly don't need O/S valves/chamber mods and that kinda thing. Plenty of results around to show that is not required at all.

[r33cruiser]

Sounds very reassuring. Cant argue with Nismoid haha

Dont worry about the tune, I have complete faith in my tuner and my mechanic.

Nitto oil pump FTW.

Tomei powered I look forward to reading up on your build.

Looks like type 2 springs are the way to go.

cheers.

Edited September 12, 2009 by r33cruiser

[R31Nismoid]

Ye - you might indeed have valve float - some have seen it, some have not.

Two example above didn't, however some have seen issues below 300rwkw so largely dependant on the condition of the head to begin with as much as anything else

[shanef]

Yet Guilt-Toy made 370rwkw with a stock head and a GT35

Admittedly it was 3ltr, but that's not the be all and end all.

I've also made 370rwkw through a relatively stock head (minor porting touch up, that's it. Stock everything else) as well with a GT30 on juice...

I think there is a lot to be said for a stock RB25 head/cams, you certainly don't need O/S valves/chamber mods and that kinda thing. Plenty of results around to show that is not required at all.

370rwkw is 34rwkw/47rwhp shy of 550rwhp though ash.

Plus show me a power, torque and boost graph of said setups with std heads and i garuantee you the better head will piss all over the budget spec ones.

[Dale FZ1]

We have narrowed it down to the 260 range. I have been advised to go 260-9.25mm lift. The reason for this, while my engine was being built we had another engine being built to basically the same specs as mine, however this one had 270-10.25mm cams. This engine had suffered valve spring issues (springs unable to cope with the lift- thats all i can recall), and recently after its final tune it broke one of its springs. Luckily no major damage was done to the engine. So if i play it safe and go the 9.25's we shouldn't run into this problem.

So, my question; Can i safely run the 260 10.25mm lift cams? Can anyone vouch for the tomei type B 10.25mm springs as being bulletproof?

Or Should I just make it easy for myself, play it safe and go the 9.25mm lift cams to give me a safety margin?

The issue with that other engine would have been coil bind ie. at that peak lift the compressed length of the springs was too long and they broke.

Generally acceptable max lift on an untouched RB25 head is somewhere around 9.0mm because beyond that to achieve satisfactory control of the valve, the valve spring dimensions come into play. Go too far and you end up with problems as above.

That all changes if/when you have machine work done to allow the fitment of longer springs.

Sounds like you need to consult with a cylinder head specialist, and someone who knows RB heads.

There are people on this forum who've achieved pretty strong running combinations without putting in big lift cams. I'd say if you pay attention to detail in the preparation of ports, matching and assembly there's no real need to go past the 9.25 260 combination.

Check the posts today by Fineline in the RB30 forum

[discopotato03]

You do have a few choices and lighter weight buckets can be had a couple of ways ie an RB25 Neo head or an RB26 one maybe with all the goodies on an R32 RB25DE block .

I'm not so sure you're going to be able to get that 370 Kw out of an RB 2.5 litre and make that power in usable form for drift or track . You are talking about getting an engine making almost 100 Hp per litre to almost 200 Hp per litre .

To get that power out of three litres means about 167 Hp per litre .

I don't think good rods and pistons cost more for an RB30 than they do for an RB25 and it's probably the same with the water and oil pumps .

I'm sure used RB30's can still be found reasonably cheaply .

Just lastly that sort of power can obviously be had from 2.5L but if it makes very lackluster power at low revs you won't like it . With three litres you have a much better chance of making std or better power down low than you have now AND the big mid range and top end as well . Sounds like an all round win for a high powered RB to me .

A .

[NYTSKY]

Mine is making a tad over 360rwkw with no porting or head mods except for step 1 HKS cams and Tomei type A springs.

Big cams and porting i think should be left to engines that see 9000 and above RPMs to accommodate the big turbo that would have to be used.

[r33cruiser]

The issue with that other engine would have been coil bind ie. at that peak lift the compressed length of the springs was too long and they broke.

Thats it mate, i believe that was the issue, good job .

I should clarify the HP. The GOAL, is 550hp, I am perfectly content with a tad over 500-520ish. BUT, if i managed to get a little bit over 550 (my goal), that would be a BONUS.

So looks like 9.25's are the safest option. Would there be a noticable difference between the 10.25's and the 9.25's?

Im guessing nothing too drastic? Power, driveability?

Edited September 12, 2009 by r33cruiser

[Tomei_Powered]

Whats the point having high hps when the engine doesnt hold up long?

I am able to push 500whp with no problem w/1.8 bar or 1.9 but imagine revving it till 9k rpm?

I would rather settle for something decent with a reliable engine.

[R31Nismoid]

More people come out of the woodwork as this thread goes

[magic1]

Quick question regarding the retainers supplied with the type 'b' valve springs, why is there only 12?

I have the 270, 9.25mm lift procams and the type 'b' valve springs, solid lifters.

We are looking at about 100thou shims but cant figure out why the kit only supplies the 12 retainers, any guidance appreciated

tris

[magic1]

will post dyno charts after fitting

surely someone in Australia has done this to a rb25

[femno]

Sounds like the head is going to be over-spec'd for the turbo really. As already said porting and big cams are only really needed for big power, and thats not really the 3582. It's going to make the already average response of the turbo worse on the 2.5.

Sure big cams can sound good, and it's awesome to tell your mates you've got a mad port job too, but seriously it's a waste of money.

If it was me id be spending the cash on a twin scroll setup, which will actually make the car nicer to drive.

[magic1]

Sounds like the head is going to be over-spec'd for the turbo really. As already said porting and big cams are only really needed for big power, and thats not really the 3582. It's going to make the already average response of the turbo worse on the 2.5.

Sure big cams can sound good, and it's awesome to tell your mates you've got a mad port job too, but seriously it's a waste of money.

If it was me id be spending the cash on a twin scroll setup, which will actually make the car nicer to drive.

im running a gt35r i don't think that the cams or the head work is over the top.

[magic1]

well we did get it sorted.

untuned as yet but here is a little sneak peak.

[discopotato03]

RB25 and possibly RB26 heads have a minor problem in that the ratio of exhaust to inlet valve size falls a little short . I don't remember the exact numbers but I think Gary (SK) told me that the sort of ideal was the exhaust was supposed to be ~ 73% of the inlet valves area and I think std 25s and 26s are about 69% . This is really easy to fix with a set of (I think) 1/2mm oversized exhaust valves which Ferea and one of the other manufacturers make . They are not expensive in the scheme of things and better than OE Nissan ones . All the machinist needs to do is remachine you std exhaust valve seats and then in like std ones they go .

His R33 and mine both have these and with 256 Poncams work really well , lost nothing anywhere . Their R33 used a GCG OP6 Hi Flow so turbo wise it was conservative according to some people . Scotty at Insight tuned that one and was impressed that the power didn't fall away at the top end of the rev range . Both engines had their springs tested and went back in with minor shimming more to suit the boost pressure on the backs of the inlet valves , and obviously set not to coil bind .

I would do this (exhaust valves) to any 25 or 26 head because its so easy , valves are not really a bolt on like cams are but can improve breathing without going too far .

Personally I would do this and experiment with cams later and the thing to remember is that the more you do to an engines top end cam and spring wise the harder it works things mechanically . Big cam lobes springs and revs is where wear and potential destruction lives so if you can get breathing improvements with a low stressed valve train so much the better . If you can have better breathing with no loss of torque and drivability anywhere thats a real bonus IMO .

People here are telling you that you may not need to over invest in your top end to get the results you seek , if you go too wild it will cost you power and drivability at around town revs and speed and that makes cars not nice to drive . You introduce increased wear and tear and maint issues because of it .

Just my thoughts cheers A .

Edited August 8, 2012 by discopotato03