Cams for RB25DET

[Merli]

Originally posted by GTS-t VSPEC

Merli,

Wow, I thought the GT3040 would have more lag than that, but it sounds like I was on the right track for what I want. I will hold off on camshafts aswell, probably just adding adjustable cam gears on factory cams once I have the internals in.  

What duration and lift camshafts are you considering? I was told that 256/264 gives a nice streetable setup, but other have told me to go for 264/264, whats your opinion? The other thing I was told was to get camshafts that remove the NVCS, I'm not sure the logic behind that do you?

Anyway thanks for all the advice, I can't wait to put the forged pistons in etc. Are you overboring the engine to lower the static compression of fitting a metal headgasket?

See'ya:burnout:

There are a few Japanese companies that manufacture camshafts for the RB25 that allow you to keep you NVCS, but I want to put the RB26 rocker covers on, which doesn't have the mound for the NVCS sensor, so I'm going to have to get rid of it... Lame, I know.

I was looking at 264/264, which as much lift as I could get away with without machining the head.

I will me ordering 87mm pistons (86mm stock, so that's 1mm or 40thou overbore)... I also have a 1.6mm HKS Metal Head Gasket sitting next to me which will lower compression to 8.6:1, which should be low enough, so I'll get the pistons at factory compression.

[GTS-t VSPEC]

Merli,

I'm going for 8.5:1 compression pistons (86.5mm) rather than the metal headgasket, the tuners I've spoken too do not recommend them, they said to stick to the factory headgasket.

If I'm sticking with the RB25 head then I won't be able to have as high a lift right? Due to putting too much strain on the hydraulic lifters?

Which pistons are you going to use, and how much did they cost? (If you don't mind me asking.) The 264/264 will give you more power but shift the power band higher?

See'ya:burnout:

[GiJOr33]

this thread is a good read.

I've got a big turbo as well (i think a HKS3040, have to have a better look when i put it up on the hoist to do my clutch). It doesn't really produce much before 4000rpm... I need to find a way to get it to spool faster as the car is a bit sluggish off boost... means it's harder to zip past someone unless i wait for the boost to wind up, and then i'm over the speed limit.

i've been looking at having a play with the RB30/25 hybrid... the extra half litre will spool it faster

what about RB25DE cams? are they hydraulic? cos i've seen in a few threads that they have bigger lift/duration (sorry, i don't know shit about cams, just read they are a good upgrade for the RB25DET).

Cheers,

Andrew

[GTS-t VSPEC]

GiJOr33,

Extra capacity will certainly cause it to spool faster, but the RB30 conversion is quite alot of work. I think that with adjustable cam gears you will be able to get it to spool faster, or you can run and anti-lag system, but this is not much good for the road, too bloody noisey.

Hopefully Merli will have some good suggestions as he has the GT3040. I have heard that the RB25DE also has a higher lift, I'm sure I've read a thread on it before, but the duration will not give you much in the way of power increase.

See'ya:burnout:

[Merli]

Originally posted by GTS-t VSPEC

Merli,

I'm going for 8.5:1 compression pistons (86.5mm) rather than the metal headgasket, the tuners I've spoken too do not recommend them, they said to stick to the factory headgasket.

If I'm sticking with the RB25 head then I won't be able to have as high a lift right? Due to putting too much strain on the hydraulic lifters?

Which pistons are you going to use, and how much did they cost? (If you don't mind me asking.) The 264/264 will give you more power but shift the power band higher?

See'ya:burnout:

Did your "tuner" explain why he thought that (re: gasket)? At 2 bar boost (which I'm planning on running), I can't see the factory gasket holding that for very long, so I've decided a metal gasket is more suitable.

I'm sticking with the RB25 head, but putting RB26 solid lifters in, allowing higher lift and higher revs.

I am still tossing up between Tomei and JE pistons. Both would be around $1800-1900 for the set of 6.

When you have a turbo as large as the GT3040, especially the HKS version which is optimised for high boost (1.6-2.0 bar) and high power, you don't want to restrict it's breathing by putting too small a duration cam in there... So when I get around to doing the cams, I'll do more research and find the best compromise between drivability and high-rev breathability

[GTS-t VSPEC]

Merli,

The tuner said that he had see so many cars come in with leaking aftermarket metal headgaskets that he only uses the factory one, which he has no problems with even on his 600rwhp Skyline. I don't know the answer, I just listen to what everyone has to say and then make a judgement call. That's the benefit of the forum, you can have lots of opinions, but eventually you will need to make your own decision and live with it. I haven't made my mind up fully yet though.

I can get some Weiseco quite a bit cheaper than that, even with shipping to you, around $1400 here plus shipping to you.

See'ya:burnout:

[whatsisname]

Merli / GTS-t VSPEC,

Have a quick read of page 3 in this thread (ignore the first 1/2 of the page) MR HPI (Martin Donnon) has some interesting points on both the h/gasket & compression issues!

Edit -It'd help if I actually post the link http://forums.skylinesaustralia.com/showth...25&pagenumber=3

Cheers

[rev210]

What about 'O' ringing BTW?

[GTS-t VSPEC]

Whatsisname,

Thanks for the thread reference, I had seen that the 3-litre had high compression in the latest HPI, I'm not sure if the reasoning was satisfactory for me, but you can't knock the fact that it will be a fast car. Martin raises some interesting points, 1. the factory head gasket is good for some impressive power levels, 2. what we do with compression here is different to what the japs do.

I'm not sure what we learn from all of this, sometimes too many opinions can make you more confused. It seems interesting that most japs run lower than factory compression while the aussies run higher, may be due to the fact that we all tend to run full-programmable management rather than piggy-backers.

I am thinking about O-ringing with the factory gasket.

Thanks for the added info, maybe you could persuade Martin to make some additional comments on this thread to enlighten us on the higher compression issue.

See'ya:burnout:

[Merli]

Originally posted by GTS-t VSPEC

I can get some Weiseco quite a bit cheaper than that, even with shipping to you, around $1400 here plus shipping to you.

See'ya:burnout:

Yeah, Wiseco pistons are the cheapest I have found too... But I have been led to believe that they aren't quite as good as the Japanese forged pistons... Remember that not all forged pistons are equal You get what you pay for in other words... This is what I've been told anyway... I can't say I've done any testing to prove that the Wisecos aren't as good as the $2500 Japanese pistons.

With the Wisecos at $1500 (my price) and the HKS/JUN/GREX pistons at +$2300... I thought I'd go the middle ground and aim at $1800 pistons (JE or Tomei)

[GTS-t VSPEC]

Merli,

There are a number of very quick cars running Wiseco pistons, the 10/9second R33 GTS-t from Sub-zero. I think the difference in price is more a reflection on where that are built rather than workmanship, labour costs a fortune in Japan, thats why there parts seem so expensive.

Thats not to say that the Japanese brands aren't of the highest quality, but are they worth the extra money? For my purposes I don't think the Wiseco pistons will have any problems, but I must admit the Tomei know there shit.

Either way the faster we get rid of the shitty factory ones the better.

See'ya:burnout:

[Guest GT N1K]

moving back into the topic of cams. I have to say this thread has helped bring into perspective more bout cams. I am buyin cams now, and opped for either HKS or JUN for my RB25DET. The price difference - bout $1000 - this includes cam gears, springs if needed & of course cams. HkS - iwas told dun need 2 change the springs when purchasing cams. does the amount of 100 extra rwhp sound dramatic when ading cams. tats wat i was told wuld b achieved.

Well i have dyno tuning on monday. so i'll let u kno 1st hand without cams and the gears, and later with them, and the chnge in rwhp.

Yup all mods on my car - full engine rebuild - forgies, conrods,balanced bottm end, knife edged, ported, larger throttlebody, larger platnum, Garrett T66, bigger injectors, haltech ECU etc etc... so i'll keep u informed for better knowledge.

once again cheers for clearing the smoke in my head concerning cams. especialli bout the midrange hole when NVCS is removed.

N1K

[GTS-t VSPEC]

GT N1K,

With the sort of setup that you already have the I would imagine that 100hp would be achievable, depending on how wild a cam separation angle you go for. You may won't to think about whether you want top end power, or more useable mid-range as it will require different tuning.

I'm sure we would all be very interested in what you achieve and how the drivability is affected, make sure you give us full details of lobe separation angle, inlet vs. exhaust overlap, lift on the camshafts, power and torque difference. Post the before and after of the dyno readings when you get them.

By the way who is doing this for you, fitting and tuning. I will be especially interested to see what difference not having the NVCS makes.

Thanks for the post, good luck with the tuning.

See'ya:burnout:

[Guest GT N1K]

u seem to kno much of wat ur talking bout. I could use ur knowledge about this time.

I just spoke to my mechanic and its true bout HKS Pulleys being unreliable. He suggested the use of Tomei or Jun, which might not look as commercial & aesthetically pleasing but are much more dependable.

I will keep u all posted and hope the best for monday.

cheers guys

N1K

[GTS-t VSPEC]

GT N1K,

I just saw you drive past on Albany Highway 5mins ago. I am trying to organise a purchase of a number of sets(~5) of cam gears through Sub-Zero. They have Toda cam gears, that whilst not looking as good as the HKS ones, have an additional bolt to hold them on. They are also used on the Sub-Zero 9sec GTS-t therefore reliability must be good.

They cost $165 each, much cheaper than I can get the HKS ones here, and I'm inquiring as to the delivery. I'm hoping on getting a few set over in one shipment therefore splitting the cost of the freight. I think that would make them ~$190 each landed. If you or anyone else is interested let me know.

I have heard the same issues relating to the HKS cam gears, therefore I am looking at this option. I know the JUN ones are even more expensive, mainly due to the name, and Tomei have a good reputation. It's alway going to be a pot-luck when getting engine parts, so you can only go what people tell you.

If you let us know how Monday goes then I'll tell you the response I got from Sub-zero.

See'ya:burnout:

[Shik]

I might be interested in a perth group buy.

[meggala]

I can get cosworths if you are interested and no they dont cost the earth .

let me know if your interested

[GTS-t VSPEC]

Hi Meggala,

I think it would be worth finding a price for these as it helps all on the forum to know what kind of prices are available. I know that I am sick an tired of paying very expensive prices on the same items.

For instance, I was quoted $290 per HKS cam gear today, retail price. I can get them for ~$200 landed from nengun, in a 5 set group buy, through sub-zero at about the same price.

If you can get a price then let us all know, so we can tell the retailers to shove there inflated prices. I don't mind them making a profit, but some of ther markups are ridiculous.

Thanks mate.

See'ya :burnout:

[Guest GT N1K]

I am presently sourcing the cams + pulleys for myself from a variety of places east and Japan. inquiring Tomei, Jun, Toda, Hks and ther recommendations. I'll find out by Mon. if Toda is the go i'll be in with u to purchase. Or if i am able to get them cheaper i'll post it up.

N1K

[Gradenko]

Another option, for those of us who want to keep VCT and be able to adjust cam timing, is to slot the factory inlet gear. I don't know if its possible in our case, but I have heard of other factory gears being modified to adjust timing without trouble.

I'd still go with an aftermarket gear for the exhaust cam though, as lighter wieght gears have their advantages.