Valve Train

[rimbimbambo]

I've been doing some research on building a head properly. I'm new at this stuff and the majority of it I wont have any experience with, so I thought I'd put up a thread and see what people can give for insite on how to build the best head possible. Specifically I'm looking at Cams, Valves & springs. this stuff kinda spurred from this article.

http://www.popularhotrodding.com/tech/0607phr_camshaft_basics/index.html

I know its written off of a hot rodding site, which may not be the best place to get my tech from, but hey its a good place to start.

I'm also looking at building with response & torque in mind, so I'm not trying to get a peak hp number.

I guess the biggest thing I found was that lighter everything was better. Also there was some mention about Beehive springs vs Parallel wound. Can you get those for an RB26? Any manufacturers?

How about replacing the valves... There was some mention on titanium, except that it cost an arm an a leg. Also some stuff about stainless hollow valves to decrease the weight even more.

Anything else I'm missing in here? Can anyone give me any specific products?

Maybe some Cam suggestions w/ specs?

[JD74]

Maybe some Cam suggestions w/ specs?

Before asking this, you really have to lay out your GAME PLAN and desired RPM/Power Range. Also, do you want RESPONSE? or all out POWER ? Low end ? Top End ? Happy Medium ?

There are tons of CAM combinations that you can go with to achive what you want, rather than just buying a matched set off the shelf in "Easy" or "Poncam" packaging.

I am going to stay onboard for this thread as well, because I am in the same boat. I want a strong low end and essentially want to tune for peak performance under 8,500 RPM.

The trick for me is trying to find a combination that will give me the low end response that I want a decent Spool without running out of breath on the top end or perhaps choosing wrong and fitting the motor with a valvetrain setup that will efectively push my Power Band up too high in the RPM range.

It's basically choosing the lesser of each 'Evil'.......or whatever works for you.

Pick a Power Band/RPM Range (ie. 3,000RPM to 8,000 RPM) - Pick a Power Delivery Goal (ie. Strong Bottom end, Mid range etc.).

Allan.

[GTR-Dad]

Nissan used some pretty decent stuff on the RB26 head. I believe the exhaust valves are already sodium filled. Big hp guys will used bigger valves, but the OEM size will provide higher air velocity resulting in better flow dynamic at low rpms and therefore better bottom end torque.

I run JUN 264 deg x 9.7 mm lift intake and exhaust cams and get pretty decent bottom end and response. Cam timing, particularly on the intake, influences low end torque vs high end power.

Here's a link to a discussion of the effect of cam timing on engine performance.

http://www.emspowered.com/vb/showthread.php?t=278&highlight=cam+timing

Pick a Power Band/RPM Range (ie. 3,000RPM to 8,000 RPM) - Pick a Power Delivery Goal (ie. Strong Bottom end, Mid range etc.).

How about 260 ft.lbs from 3800 - 7500 rpm and 300 ft.lb from 4200 to 6800 rpm? It feels pretty strong on the street and the autocross track!

Want more? I expect that turning up the boost will not change the spool response at all, but will increase peak torque and deliver higher torque at redline. The power band would narrow in terms of rpm range for 90% of peak torque, but would still deliver the bottom end tractability I currently enjoy. There would still be 300 ft.lb at 4200 rpm.

Dan

[mcfly]

The exhaust side of the rb26 head is what needs the most work.
You wont find dual springs off the shelf for a rb26 simply becasue they wont be needed for 99% of the ordinary builds. Jun springs will easily take stock valves to 10k rpm if you so desire.


And of course, with all my posts. Some food for thought to spur the discussion and ruin everyones dreams/posts before me. Big cams = big power apparently. The Mines r34 absolutely did not use small cams. This car was to be the "response king", did the job very well too. There was a discussion about it last year somewhere.


Many rb26's have made it to the 1k hp mark with stock valves.
Now we don't know what to think, but do not void what gtr-dad and jd said before me, they are two very smart cookies.

[JD74]

And of course, with all my posts. Some food for thought to spur the discussion and ruin everyones dreams/posts before me. Big cams = big power apparently. The Mines r34 absolutely did not use small cams. This car was to be the "response king", did the job very well too. There was a discussion about it last year somewhere.

Define BIG....
Long Duration ? High Lift ?

The Mine's Car (as Eric pointed out in another thread) surely did not use their 'Off the shelf' 252/10.5 Cams....but with their 'Crate' engines follow the OEM path - unbalanced in/ex...shorter duration and lower lift on the exhaust side.

[JD74]

This openes up an entirely new debate as to balanced, unbalanced, lift, duration etc.

- Intake.....Exhaust = identical spec'd

- Both Low Lift/Med Duration (9.1/264 'packaged cams')

- Intake high lift/long Duration (10.5+/272+).....Exhaust lower lift/shorter duration (10.4-/264-).

- Intake high lift/long Duration.....Exhaust Same lift/longer duration.

...and on and one.....

It depends on Power and RPM goals....no ?

[mcfly]

I can't find the thread anymore JD, ever since they moved the FA sections around it's been lame.

From experience a slightly smaller exhaust cam has made idle much easier to hold down.

Cam choice is generally rpm related(power comes with rpm though on a rb). But when you get into off the shelf cams that the companies in Japan offer, some smart person once said you can't go wrong buying any HKS, Tomei or JUN Cams.

Just my two cents. At the end of the day, the stock cams are easy to surpass with no downsides.

[JD74]

Again....BIG and SMALL......I am not sure if you are meaning Lift or Duration, or both in general....

We all want to fill the intake chamber efficiently, we want to evacuate exhaust quickly, we want a steady idle and response and maintain crank compression, we want top end power, we want low end torque......unfortunately we can't have it all and at what point does it start to negatively affect spool-up when using a smaller Exhaust Cam ?

I may simply follow the 'Mines Way' and order my Cams accordingly with response and mid-range with sub-9,000 RPM Rev Limit in mind.
(example using Jun Cams - 1 step difference between IN/EX)
Intake - 10.5 Lift/272 Duration
Exhaust - 9.7 Lift/264 Duration

I think an unbalanced set up may be right for me as a happy medium between power and response. I would really like to see some results from similarly chosen setups though.

The only problem I can see is getting too high up in Duration numbers and pushing my Power Band up too high.

[GTR-Dad]

I defer to McFly on big power topics every time! I should have said the _only_ reason I can think of to increase valve size is to go for 1k+ power.

My build is pretty mild, and is focussed on broad power band. It's not optimized yet, but works pretty well.

SAU is a good place to look for circuit build examples. I corresponded with a few guys over there when I was spec'ing my build.

Dan

[Super_Dude]

The perfect cams for your setup won't help out near as much if you don't also get a good port job from someone who knows what they are doing. Also be weary of valve springs. The Japaneses valve springs are notoriously stiff so the can handle 10K RPM. If you want big cams+durability keep revs lower (max 8500RPM) and use Cosworth valve springs. They are designed for big cams and lower revs then there JDM counterparts.

[Skym]

It's a combination of parts.

On turbo motors you have to take into account the turbo, header size / length, etc. Cam specs to turbo size are important and if they work well together, engine will perform better. The cams on the Mines demo car are designed to work with the HKS 25/30 turbo's. There is a EVO SuperLap car in NZ with Cosworth cams, Garrett turbo combo that work together. It works so well, no car could beat it around 2 different racetracks.

From what I understand increasing valve size is done when port size is increased. Then cams matched to this. Although your probably increasing top end power when increasing port size, I think losing response.

You need to talk to a head specialist, as they take turbo, cams, headers, etc into account when working out the best combination.

This is an example of the questions a head specialist would ask you -

https://www.safe.net.nz/kelford_co_nz/designshop.php

You can buy engine simulation programs, that can help to work it out with different combinations -

http://www.kelford.co.nz/computersoftware.html

[rimbimbambo]

Yeah lets just assume the power goals are between 3500rpm-9000rpm and RESPONSE is the big goal (I wanna keep everything as light as possible, but still durable).

I just wanted to point out that I thought the Mines R34 wasn't really a power machine. Isn't it only rated for 600bhp? I mean 600bhp is still big, but when you have guys getting 800+ its not really a record breaker. Also they have a note about machining the cams (I'm looking at the stage 2)?

http://www.mines-wave.com/english/CATALOG/ENGINE/COMPLETE_RB26DETT.htm

I read a bunch of posts about how people doubted that the cams the Mine's engine used weren't really what they said they were; maybe the cam numbers are before the machining. I bet the reason they machine everything down is to reduce the weight & hence increase response.

[Skym]

Stock port size is best for response.

AmeriKiwi on GTROC with Nur R34GTR had his Nur engine built at Mines with Mines cams (260 intake, 252 exhaust), N1 turbo's, etc, with 550hp at engine. Then later on fitted HKS 2530 turbo's and said the cams, turbo's worked together very well. His engine was producing around 705hp or slightly over 400awkw (dyno) on I think was 98 pump gas (I gather 94 octane is the equivalent fuel, where you guys are located). Also he had the diffheads changed to 4.11:1 R33 GTR V-spec diffheads, both front, rear. The Mines cam specs are similar spec wise to Tomei Type A Poncams for RB26.

Part of the response of the Mines car can be attributed to stockish capacity RB26, shorter final ratio in diffheads + early spooling turbo's, matching cams, aggressive ECU tuning on racefuel, semi slick or slick tyres for near to 0 wheelspin, etc. I think it's R33 GTR V-spec 4.11:1 diffheads they use in the R34 GTR, due to being a V-spec N1 chassis.

720ps would be the Garage Saurus R32 GTR -

http://www.youtube.com/watch?v=lOJjBrh6-qg

It's one of 2 purposes the car was designed for (drag, time attack). I think they run 2 different setups, depending on the purpose. Good on the HP racetracks, where you can open her up. I think is faster than the Mines R34GTR on those HP racetracks.

[rbs14]

720ps would be the Garage Saurus R32 GTR -

http://www.youtube.com/watch?v=lOJjBrh6-qg

It's one of 2 purposes the car was designed for (drag, time attack). I think they run 2 different setups, depending on the purpose. Good on the HP racetracks, where you can open her up. I think is faster than the Mines R34GTR on those HP racetracks.

yeah garage saurus have 2 engine

spec from a old modified mag i have !!!

drag : Greddy 2.7L kit TRUST T88H-380K turbine (1060 whp @ 9,200rpm/784lb-ft@6,900rpm)
circuit : OS Giken 3.0L kiyTRUST T88-33D turbine ( 770 whp @ 7,800rpm/666 lb-ft@5,600 rpm)

[rimbimbambo]

I always thought that if you wanted response you would go with a TT setup instead of a single. Also are they overboring or increasing the stroke? Pretty good time - Its in the top 5 for tsukuba time attack records. Anyone got any head specs on the M-Speed R34?

http://www.mspeed.jp/en/democar.html