RB25DET Head porting info

[Cubes]

Boostd..

Also removed the intrusive port bumps on the exhaust side of the head

Also some of the bumps near the outlet are purposeful to direct the airflow around a the bend, these need to be smoothed rather than removed.

So you removed your exhaust bumps and later was told or realised that they are functional?

Mine are still there but they have been reduced and smoothed.

[siksII]

Just some random pics from when my head was off a few weeks ago, was replacing head gasket, and while the head was off i also got it reconditioned including vavle stem seals. As far as i know, the head has not had any performance work to the ports, its only been cleaned up.

Plus a video of us replacing the head onto the block...

I have higher(700k each) quality pics if anyone wants..

http://users.tpg.com.au/adsl4lxm/Head/replace.avi

[BOOSTD]

Joel. the stud bumps were on the head, which don't help flow at all. The purposeful ones are on the manifold just near were the turbo bolts up. sorry i was as clear as mud wasn't i....

[Cubes]

I get ya..

[mambastu]

Originally posted by Sydneykid

Hi mambastu, did you equalise the capacity of the combustion chambers?

No. To be honest I didn't really want to mess around with the combustion chambers too much so I just smoothed all the chambers slightly to remove a few small casting marks.

[Mick]

how did u do it with it still on the car ?

what about the alloy fileings! Wouldnt lots of filings go right down into the exhaust ports and get caught it the valves ?

[Cubes]

Thats what I was thinking as I might remove the bumps totally in mine as they have only been smoothed out.

[BOOSTD]

stuff a rag in the out let.

[Sydneykid]

Hi mambastu, so you could have 62 cc's in one combustion chamber and 63 cc's in another? That's 9 to 1 compression ratio in one and 8.8 to 1 compression ratio in the other.

mmmmmmmmm?

[mambastu]

Originally posted by Sydneykid

Hi mambastu, so you could have 62 cc's in one combustion chamber and 63 cc's in another?  That's 9 to 1 compression ratio in one and 8.8 to 1 compression ratio in the other.

mmmmmmmmm?

Well at least it might not detonate in a few of the cylinders then

Are you telling me that Nissan deliberately left very small casting marks in a couple of the chambers and allowed for it ?......I don't think so...

Its not perfect but as I said I have removed very little material from the combustion chamber i.e no de-shrouding and I have not favoured any particular chamber. As you can see from the pictures the combustion chamber still has a slight cast finish so I haven't done much more than a polish.

I haven't measured port volume or shape either....how many head porters really do ? Not many I would guess.

This isn't the first cylinder head I've done and I've had good results in the past. I'm sure I'll be over the moon with the results. :uh-huh:

I understand you work at/own a company that sells products in Australia (and thats cool) but I don't and I'm not spending the £800 + that UK companies want to port an RB head. This isn't a head for a race car that needs every last bhp. This is going in my road/occasional trackday S13 and its to a fairly tight budget.