Power Ceiling Gt3076R

[Rolls]

Dips I've been told are like that on every car that is dyno'd at Morpowa.

Those dips are normal, if you have even more points on the graph it can look really really bad, valve float tends to have much deeper valleys from the few I've seen, could present itself in more than one way though.

If you suspect lifters, would taking say 10 compression tests show up a partially failing lifter?

[zebra]

If you suspect lifters, would taking say 10 compression tests show up a partially failing lifter?

not if they are pumping up at high revs.

Unfortunatley at 900 bucks + fitting its not something you would want to change to find it was something silly like a vacuum leak

[Cubes]

Run it up to Boostworx for a power run.

See if Shaun can throw any ideas at it. He's been doing the RB30 DOHC's (VL's) well before bl4ck32 and myself did ours years ago.

On the note of timing up the rb30's. I've never had issues. I've had the stock cams out twice and the regrinds out twice.

To time her up I'd simply line up the bottom (usually take a picture as my head won't fit) and then shove the cam belt on lightly, turn the motor in the direction of spin to line up both cam gears spot on then tighten up both tensioners at the same time.

I take her for a quick spin and check it again.

The dyno sheet attached was of mine running 5w30 oil (anything thicker would result in bad valve float)

I also had to wait until the oil was 100% warm otherwise the valves would float and lifters would pump up causing a rough idle until the lifters bled down - scary days it was.

The symptoms - top end felt flat, the dyno sheet really didn't wave around that much and it really struggled to hold on to boost up top.

Once on the road and warm thinking it was fine after giving it a bit of a hard time the top end would start to feel flat again - yeah thinking back I was playing with fire but at the time I had never experienced float as such before.

Yours - that dip looks like some spring surge/float dyno sheets i saw in the old days when I was googling my own issues.

[Rolls]

not if they are pumping up at high revs.

Unfortunatley at 900 bucks + fitting its not something you would want to change to find it was something silly like a vacuum leak

I always hear lots of stories of noisy rebuilt heads, I thought hydraulic ones were meant to be easy to adjust?

Hell even my solid lifters in my neo are quieter than my old rebuilt r33 head.

[zebra]

no adjustment with hydraulic lifters...they are self adjusting

[r33_racer]

http://www.rockauto.com/catalog/moreinfo.php?pk=1818588

Rock auto sell new 300zx hydraulic lifters for quite a reasonable price. Im sure I saw somewhere that they are the same as rb25 lifters.

Hopefully that might help.

[KiwiRS4T]

UPDATE!!!

Ok so Tomei 256/8.5 IN&EX cams + adjustable gears were put in.

Car was timed using DIAL GUAGES. Builder said that he had to run 7-8 deg advanced on the intake side and 6 deg on the exhaust side from "zero" when the dial guages displayed that the cams were in the right position ("zero'd" as you would with a standard type setup).

Car was chucked on the dyno...From what I was told in conversation, the ignition timing was measured with a gun so that the ignition timing on the computer could be verified. For some reason the timing was 10 degrees out (advanced from memory). I have no idea why this was the case as the computer was not touched since last time the thing was on the dyno. So the timing was reset in the computer.

Few runs were conducted. Timing was played with up to around 8-10 times on both the exhaust side and intake side. But the thing still wouldn't make more power than about 250RWKW. Much lower than you would expect with the cams + turbo + motor setup.

They took it off the dyno for lunch. Cooled down, then ran it again...Made about 5RWKW more.

So all up it finished with about 255.5RWKW at an A/R of about 11.5-11.8.

See dyno graph below.

A comparison - my Rb30 has just been fired up. Stock bottom end and stock RB25DE head new rings bearings rod bolts and N1 pump. Sinco manifold (similar to 6boost) Greddy copy FFplenum, HDi i/c, GT3540 with .63 ex, stock throttle body+ fpr, 550 injectors, synapse 50mm w/g , Link G4, venom cat and 3in exhaust now at 9 psi (to be tuned to 18 - 21 psi) limited to 6500:

[Bl4cK32]

Run it up to Boostworx for a power run.

See if Shaun can throw any ideas at it.

sometimes the simplest fix is to get another set of eyes to look at the problem. Ive had problems that I was pulling my hair out trying to solve, when someone walks past and notices something that was staring me in the face....

[Cubes]

With regards to lifters. Another thing I came across.

My RB20DET lifters were different to the r32 RB25DE. When the RB20DET lifters were installed in the r32 rb25de head the lifters were exceptionally noisy. The lifters when in the rb20 were quiet.

I pulled both RB20det and rb25de lifters apart all cleaned primed etc. It appeared as if the rb20det lifters would sit just that little bit lower. So if you have an r32 rb25de head another thing to keep an eye out for.

[R32Abuser]

sometimes the simplest fix is to get another set of eyes to look at the problem. Ive had problems that I was pulling my hair out trying to solve, when someone walks past and notices something that was staring me in the face....

Agreed.

After a few weeks of driving, I'll probably take it to Shaun or another workshop in mind to look at the top end issue.

With regards to lifters. Another thing I came across.

My RB20DET lifters were different to the r32 RB25DE. When the RB20DET lifters were installed in the r32 rb25de head the lifters were exceptionally noisy. The lifters when in the rb20 were quiet.

I pulled both RB20det and rb25de lifters apart all cleaned primed etc. It appeared as if the rb20det lifters would sit just that little bit lower. So if you have an r32 rb25de head another thing to keep an eye out for.

IIRC my lifters in the head on the RB25/30 are the standard RB25DE lifters. These have been cleaned/bled. However there are still one or two (or many!) noisy lifters according to the builder. I think replacing them could be an option...However, as you have stated, there is a difference between the RB20DET and RB25DE lifters. I just don't know how I can be sure without physically measuring them (or someone kindly doing it for me on a motor they have ) and contacting the company R33_Racer stated earlier and sizing it all up.

Guess I'll have to explore these avenues!

[zebra]

Kinda off topic, but whats the most power anyone has made using a 25DE head?

[Crans]

Very off topic, but isn't this a paradox?

As seen in Zebra's Signiture:

D_I_F, on 04 May 2011 - 06:10 PM, said:

OMG I'm in Zebra's Sig!!! f**k I must be cool!

How can this not destroy time and space? Or do I just enjoy my Monkey Island/Doctor Who too much?

[zebra]

Well...If I said I was typing this from the Tardis would you believe me? lol

[R32Abuser]

Just at a glance I would say that sky30 would have made the most.

306 RWKW IIRC.

That or cubes ~ 30X RWKW

[R32Abuser]

FYI

http://www.skylinesaustralia.com/forums/topic/225053-for-the-engineers-hydraulic-lifter-design/

[r33_racer]

so ca, vg and rb lifters are all the same. so that means that option is available at a reasonable price.

[R32Abuser]

They may fit one another's motor. That doesn't necessarily mean that they are the right lifter for that motor though- as per Cube's comment and the thread I linked to a few posts above. Cube's said that the RB20DET were marginally smaller- this caused the valve train to be a tad noisier.

[r33_racer]

well its the vg lifters which are in question as they are the new ones for sale. We just need a vg lifter measured up.

[R32Abuser]

Yup.

Im already on this. Sent an email to that supplier you kindly listed re: dimensions. Once I get a reply (if they are willing to share) we can compare to the RB25DE/Other hydraulic lifters.

Hopefully they are a suitable replacement...at least for my wallet's sake!

[JonnoHR31]

i have a full set of s1 rb25det lifters sitting outside i can measure if you need any measurements