Spotto This Head..

[GTS4WD]

Hey guys..

I got an RB25 head for a 25/30 build.

Dont be turned off it.. It needs a good clean but internally its in very good condition.

Now.. I have a question.. Is this a VVL head? Because I noticed that it has the enlarged ends at the cam shaft covers. I noticed that my dads RB25DET VVL has these too. Below is my RB25DE head out of a Staggy or 33. Note that its Does not have the same bulges comming out of the the camshaft covers.

Any ideas?

Edited June 4, 2008 by GTS4WD

[dano4127]

Yup thats got the VCT

[GTS4WD]

Yup thats got the VCT

VCT or VVL?

Because I know R34's have a VVL (variable Valve lengthening) heads. And I have noticed on R34 RB25DET's they have the bulges at the back of the head (closest to the firewall).

The head I just bought has these same buldges at the back of the head.

My Rb25 out of a staggy/R33 GTS4 does not have them. R33's do not have VVL technology either.

So Im curious to see if the head I bought has VVL.

And if so.. how do I "fuel" it for a 3L build?

[Spoolup]

VVL - Im ( And Im sure alot of others ) are keen to hear how that one works - pls explain.

Edited June 4, 2008 by Spoolup

[GTS4WD]

Nissan Ecology Oriented Variable Valve Lift and Timing (commonly known as VVL) is an automobile variable valve timing technology developed by Nissan. VVL varies the timing, duration, and lift of valves by using hydraulic pressure switch between two different sets of camshaft lobes. - Also Known as NEO - Hence the 'NEO' engine cover on R34's.

There are HUGE power figures that can be extracted out of these engines.

You can also get;

SR16VE (found in VZ-R. Its an N15 pulsar with ~150 NA KW - Common in NZ)

SR20VE

SR20VET (Jap spec X trail)

There are poeple that are pulling out 200 NA KW out of 2L 4cyl's

Edited June 4, 2008 by GTS4WD

[Spoolup]

Interesting - but I can assure you this technology is not in any R34 NEO heads except for the vaires timing and duration - the lift is fixed.

Edited June 4, 2008 by Spoolup

[GTS4WD]

Interesting - but I can assure you this technology is not in any R34 NEO heads.

Well then what does NEO stand for?

As far as I am aware, NEO VVL goe hand in hand..

What is the NEO technology in the R34 heads then?

[Spoolup]

No idea what the NEO part stands for - But they are a solid lifter head - the valve runs off a solid lifter that runs off a solid cam lobe.

[GTS4WD]

mmkay.. so why the buldges?

Did your NEO head have these?

What is the diffrence between the 34 and 33 RB25 heads then?

[Spoolup]

I think it is just the tappet cover designs - maybe the breathers.

The difference between the heads are:

R34 are solid lifter

R34 has different valves

R34 has smaller combustion chamber

R34 has a different setup to feed oil to the VCT soleniod

R34 has different valve springs

And prob some others Ive forgotton

[nizmonut]

1995 97 series 2 R33 rb25det NVCS.

found this on the net, might be helpful

Let's start w/ the function of the VTC assemblies. These assemblies are mounted on the intake cam. So there are two total. At a certain rpm/load, the VTC solenoid is de-activated and oil stops flowing to the assembly. This allows the intake cam to rotate and advance up to about 8-9 degrees. This helps high rpm hp and torque.

Now because these assemblies are hydraulicly operated(engine oil pressure) this is where the problem begins. The VTC assemblies are very high up on the heads(see sig pic for reference) This means during start-up these assemblies are probably the one of the last things to get oil. Along with this, the oil gallies leading up from the oil pan are fairly small. So any clogging of these gallies from sludge will only slow the time and quantity of oil that these assemblies receive.

Indications of VTC failure. Usually you will hear a *tick* when the car is cold(like a loose valve tick) and it will go away after a few seconds. When they start to get worse you will hear the tick when the car is warm and you must *lug* the engine is low gear to get rid of the tick. Finally the damn things will tick all the time! I think what's happening is that the springs inside the assemblies slowly start to get weak when they don't get enough oil.

Preventative maintainance. The best thing you can do to prevent VTC failure is to CHANGE YOUR OIL REGULARLY. Remember sludge is the enemy here. Also using a oil filter that has the proper anti-drain back valve is also important. This keeps the oil pressure up as much as possible when the engine is turned off. This gets oil to the upper heads as fast as possible durning start up. Nissan oil filters are recommended and Nissan choose to use a special filter for the 92-94 SEs. Not the standard "blue" Nissan filter. Also consider switching to synthetics if possible.

Edited June 4, 2008 by nizmonut

[GTS4WD]

Indications of VTC failure. Usually you will hear a *tick* when the car is cold(like a loose valve tick) and it will go away after a few seconds.

dang.. I hear this..

Thats for that nizmonut, much appreciated

[R34GTFOUR]

the basic principle how vct works is the exact same between the r33 and r34.

The neo head in the r34 is called a neo because of its reduced emissions, the vvl neo heads on the sr20 are very very different.

the r34 neo head does not have the same technology as the neo vvl sr20 heads.

[R34GTFOUR]

actually while i think about it, can you do me a massive favor. Can you measure the amount of cc's each combustion chamber holds in your neo head? If you have access to a plastic syringe that has measurement markers on it, you should be able to work it out. You'll probably need to know this so you can get the correct pistons/headgasket to get the best CR, but i'm going to be doing it with my neo head aswell and i've heard that they have a combustion capacity from 51cc to 54cc.

Also any reason you went the neo head? were you hoping for vvl?

Edited June 5, 2008 by R34GTFOUR

[Sydneykid]

SR20 's have rockers , RB's don't The cam lobes work directly onto the buckets, that's why you can't have variable lift in RB's.

Cheers

Gary

[GTS4WD]

SR20 's have rockers , RB's don't The cam lobes work directly onto the buckets, that's why you can't have variable lift in RB's.

Cheers

Gary

hmm.. I never thought about it that way..

Logic makes things so simple..

Thanks mate,

I guess that I picked up was SII

R34GTFOUR, Im at uni at the momement and the head in Sydney.

If I can confirm its a VVL, Ill pm you

Edited June 10, 2008 by GTS4WD