Best place to source mild cams for the RB25det quickly and cheaply

[Steve]

Another thought Matt, put the stocker back on the inlet, reconnect the NVCS, use the inlet adjustable cam for the exhaust side, sell the inlet cam as an exhaust cam, and you can have your bottom end response back with extra mod money:)

[Cubes]

According to the engine dyno sim's the stock inlet cam is pretty spot on for the 2.5ltr. If you increase the duration you gain very little up top but a noticable amount down low.

However if you were running a 3ltr then increasing the duration on the inlet to around 260 you actually pick up power both down low, mid and up top.

Exhaust cams is where the gains are if the cams were origionally designed for that capacity motor.

But then again its only a software sim. is it right? I would like to know if the larger duration inlet cams really do pick up power with the 3ltr bottom end.

I was under the impression inlet cams cannot be used as exhaust cams due to the CAS?

Can the RB25DET cams be used on the R32 RB25DE head?

[Craved]

So to answer your question we have run 292 @ 9 mm without "headwork".  We also have run 264 @ 10.5 mm and done headwork.

To answer the second question, based on my personal experience;

240 is standard GTST

248 is standard GTR

256 is a good mild street upgrade, go for 9 mm lift

264 is a good combo (street, track, circuit) go for 10 mm lift

272 is a good for circuit work at 10.5 mm lift

Hope that helps

SydneyKid, with the 264 with 10 mm lift, is it only the grinding of the head for clearance you need to do, or are the valve springs etc changed. looking at options to go with a HKS gt3040 on an rb25 to be used for street,track,circuit!

[Sydneykid]

SydneyKid, with the 264 with 10 mm lift, is it only the grinding of the head for clearance you need to do, or are the valve springs etc changed.  looking at options to go with a HKS gt3040 on an rb25 to be used for street,track,circuit!

Hi craved, we change valve springs at anything over 9.5 mm lift. Plus, with the GT3040, you are going to be able to run over 1.3 bar which is the rule of thumb limit I put on standard RB25DET valve springs. That's my 2 reasons for changing valve springs, the 3rd is RPM. Anything over 8,500 rpm is a real good reason as well.

Hope that helps

[Craved]

Hi craved, we change valve springs at anything over 9.5 mm lift.  Plus, with the GT3040, you are going to be able to run over 1.3 bar which is the rule of thumb limit I put on standard RB25DET valve springs.  That's my 2 reasons for changing valve springs, the 3rd is RPM.  Anything over 8,500 rpm is a real good reason as well.

Hope that helps

it does help thanks,

what is the limit of the of the standard crank in terms of rpm? do these cams assist in increasing the rpm limit of the engine? (still learning)

also currently the GT3040 is running a 1.12 exhaust housing so will be pretty laggy, with higher lift will that help spool this up quicker?

[Sydneykid]

Hi Craved, my thoughts follow your questions..........

what is the limit of the of the standard crank in terms of rpm?

I really don't know, there are so many things other than RPM that cause problems with crankshafts. If you need to rev it, chances are you have increased the other items like combustion pressure, torque loadings, clutch initial grab etc. We have certainly used 9,000 rpm for 400 rwkw without any problems. But maybe 9,000 rpm and 450 rwkw is, or 9,500 rpm and 350 rwkw. Obviously if the crank is balanced and lighter rods and pistons are used this increases the crankshaft lifing. I have seen over 1,000 bhp out of a standard RB30 crank and I have seen a standard RB20 crank rev to 10,500 rpm. There are to many possible combinations to give a definitive answer.

do these cams assist in increasing the rpm limit of the engine?

They will certainly increase the rpm range that it can operate in efficiently. Generally speaking the standard cams start to top over at 6,500 rpm. You should find that this sort of timing and lift will push that up to 7,500 rpm and if decent port work and exhaust (manifold, wastegate and pipework) are used then 8,000 rpm is not unusual. That's not the rpm limit, just where the power starts to drop off when an appropriately sized turbo is used.

also currently the GT3040 is running a 1.12 exhaust housing so will be pretty laggy

What capacity is the engine?

with higher lift will that help spool this up quicker?

Yep, that has been our experience. As long as the duration doesn't move the power band outside the required spool up rpm.

Hope that helps some more

[Craved]

I really don't know, there are so many things other than RPM that cause problems with crankshafts.  If you need to rev it, chances are you have increased the other items like combustion pressure, torque loadings, clutch initial grab etc.  We have certainly used 9,000 rpm for 400 rwkw without any problems.  But maybe 9,000 rpm and 450 rwkw is, or 9,500 rpm and 350 rwkw.  Obviously if the crank is balanced and lighter rods and pistons are used this increases the crankshaft lifing.  I have seen over 1,000 bhp out of a standard RB30 crank and I have seen a standard RB20 crank rev to 10,500 rpm.  There are to many possible combinations to give a definitive answer.

wasn't really looking to go as far as 9,000 rpm , maybe 8,000rpm max, using standard rods/pistons at this stage.. dont wanna spend up crazy just yet!

They will certainly increase the rpm range that it can operate in efficiently.  Generally speaking the standard cams start to top over at 6,500 rpm.  You should find that this sort of timing and lift will push that up to 7,500 rpm and if decent port work and exhaust (manifold, wastegate and pipework) are used then 8,000 rpm is not unusual.  That's not the rpm limit, just where the power starts to drop off when an appropriately sized turbo is used.

sweet, that really works with my above mentioned target/thoughts (not sure which yet!)

Exhaust housing will be made by myself and a mate, high mount customs dump to 3 1/4" exhaust. head port and polish is something ive thought about but not found someone that i know has worked with these, will hit my mechanic up with all these new options im getting... most of the work will be done by myself though!

What capacity is the engine?

standard rb25! still working on the compression that i'll be running! do you know what the standard compression is for the rb25, and the size of say a standard nissan headgasket for them too...?

Yep, that has been our experience.  As long as the duration doesn't move the power band outside the required spool up rpm.

so it's all about the tune as everything is, but it will be better than running standard cams.

Hope that helps some more

thanks SK, heaps more to think about than i initially thought, so your helping me along the way!

[Craved]

one more thing... do you need the head removed to change the cams on the rb25? i know on bmw's ive worked on need the head off the car to access the cam. this goes for the grinding needed to clear the cam lobes too ..

cheers

[BOOSTD]

Cams can be fitted with the head on. Grinding can also be done with the head on. Just clean up thoughly.

[BOOSTD]

Another thought Matt, put the stocker back on the inlet, reconnect the NVCS, use the inlet adjustable cam for the exhaust side, sell the inlet cam as an exhaust cam, and you can have your bottom end response back with extra mod money:)

Has anyone done this? I am yet to try retarding the exhaust side. I bought another cam gear yesterday and will fit tonight.

Sydneykid, have you had experience with this setup, I would like to know if it would loose me alot of power up to for more down low... I might be best keeping both cams if the exhuast retard helps.... grrrr that's it I'm putting it on right now.

[BOOSTD]

I'm confused now, I have the wheel on (OS Giken). What is -4degrees. The marks are spaced twice as wide as the HKS cam gear. do I set it to the forth mark? that would equal 8 degrees at the crank tho....

pls help

[BOOSTD]

Cam gear has been installed.

After some research I came to the conclusion each pulley is 720 degrees with 48 teeth which equals to 15 degress per tooth. 4 degress equaled one mark on my OS cam gears. So I set the exhaust to -4 and intake to 2(half a mark). The difference is quite noticable with more power everywhere. Compared to with the VCT off boost is now about the same. Does come on boost(4300-4500) with more of a rush than with standard cams and -4 cam gear. So I figure the new 264's are helping more than just at 6000 rpm were power appears like a light switch.

[Mesmer]

Ok i need some help and here looks to be the right place.

I bought some Tomei 256 8.5mm cams off this forum.. now when they arived i opened the box to find something looking exactly like the stock cams in my engine. We couldn't measure any differance in lift so I took them to a cam place and they said they are exactly the same as the old one.

Now this isn't a huge problem because the seller said he would refund my money even though he was sure he sent me the right cams.

So I would like to know for sure before I send them back.

Do tomei put any identifing marks on there cams?

Do they still have the stock "S6" or "U5" cast in them at the back?

anything else that may help etc

Thanks

John

[Steve]

If it doesnt have tomei markings, how would you know its a tomei cam?

I have hks 256/8.8 inlet, and side by side with the stock cam, its alot larger. Send them back.

[BOOSTD]

I have Tomei cams. Mine have 264 8.5mm stamped on the rear bearing. The stockers have nothing. The difference is very noticable just from looking at the two side by side. Measure the lobe height and if it is 7.8 max then they are stockers. I think 8.5 is the smallest lift you can get.

Steve: I can't swap the inlet cam for exhaust as it doesn't have the CAS keyway. Is making more power than the VVT now anyway (since I turned my cams gears the correct way...hehe opps)

[Pandaemonaeon]

I'm not 100% on all this and am looking at getting some cam work done. I've done a bit of researching and it seems that I should go for a 270 duration with 9mm lift. Should I be using the same for both intake, and exhaust or different profiles? Next question I have is when talking to the shop about the cams I was told that the Rb25DET has two different cams that are used, with one cam set bigger than the other. With these differences is it possible to interchange these cams between engines, or can you only use the bigger/smaller cams in an engine that originally came with these bigger/smaller cams?

[Sydneykid]

I've done a bit of researching and it seems that I should go for a 270 duration with 9mm lift.

Our experience has been that it is pretty much a waste of time going for long duration (270 degrees) with low lift (9 mm). You end up with an unneccessarily lumpy engine that doesn't make equivalent power. For a road, sometimes track, car you would be better off with 264 degrees at 9.5 mm lift or much better with 264 degrees at 10 mm lift. For a mostly track car, I would use a 272 degree camshaft with at least 10.5 mm lift.

Hope that helps

[BOOSTD]

Our experience has been that it is pretty much a waste of time going for long duration (270 degrees) with low lift (9 mm).  You end up with an unneccessarily lumpy engine that doesn't make equivalent power.  For a road, sometimes track, car you would be better off with 264 degrees at 9.5 mm lift or much better with 264 degrees at 10 mm lift.  For a mostly track car, I would use a 272 degree camshaft with at least 10.5 mm lift.

Hope that helps

OK so the longer the duration the later power will be in the rev range and a lumpier idle. Is there any disadvantage from going higher lift ?? 8.5mm on my 264's seems abit low. Would there be much advantage from going to 9.5mm lift? Without upgrading springs that is. Power comes on very hard at 6000rpm with the 264's. I wouldn't want it any later. My head is also majorly ported. Is higher or lower lift better suited to a ported RB25?

Sorry for all the questions but Julian's 21st Century Performance book doesn't help much.

[Pandaemonaeon]

Got the numbers wrong sorry. It should be 260 with 9mm of lift that I was wondering about. The 270 is with 10.5mm lift and pretty much for track use according to the info I was using.

[Craved]

Cam gear has been installed.

After some research I came to the conclusion each pulley is 720 degrees with 48 teeth which equals to 15 degress per tooth.

each wheel should be 360 degrees with 7.5 degrees per tooth.