Rb 25 Head Porting.

[BlackBox]

Hi,

I am doing a round of modifications to my r34 gtt rb25 neo that is basically copying a setup that should make ~330 RWKW on 98

Is there much to be had at this level from getting the head ported?

The engine has 100,000 km on it so could be due for a freshen up top, I was planning on doing stem seals since I am replacing cams and springs anyway but was going to leave the head on, but this would be a good time to pull the head off and get it ported if the gains made it worthwhile and install some arp head studs.

I read on the 'Lewis engines' website and it seems like a worthwhile upgrade, is there any machining shops that would come recommended by SAU members?

[Ben C34]

Porting the head will result in gains.

Whether it is cost effective is another issue.

[GTSBoy]

What he said.

At 330rwkW there is absolutely no need to port the head. It is very possible to get to that sort of power just by using boost. If you do port the head, you will need a turbo that can make the target air flow level at lower boost. This might ultimately mean the difference between using a GT3076 or a GTX3076 (just to pull an arbitrary turbo size out of the air. The GTX are optimised to make power at higher pressure ratios.

If you do port it, and it is done well (sensibly, not just hogging shit out of it) then gas flow will increase even before the turbo is up on boost, so you should improve response.

But.....How else would you spend $2k?

[Blackkers]

ARP headstuds are never a bad idea but probably not needed for your goals

no need to remove the head to change them out though

[AngryRB]

Better off with a set of poncams and some E85/water meth..

[BlackBox]

My setup will already include a hta fp 3076 and tomei pon cams.. Unfortunately e85 isn't an option for me but I haven't ruled out a shot of gas ?

[mitchum]

cleaning up the bowl area, port matching and taking out the humps can be done at home for alot cheaper than 2k

[GTSBoy]

And I would not call that "porting" either.

[Ben C34]

Anyone can hack up a port.

[scotty nm35]

Anyone can hack up a port.

Seen it too many times to mention.

The more boost you run the less runner size you want imo, so a little bowl work is fine, and I agree with port matching, but I would like to actually add material to the port to increase the gas speed before the valve.

Just think how long the valve is open for at 8000 revs, and what speed the air needs to be going to fill the cylinder in that time...

[BlackBox]

I wouldn't attempt to do it myself, anybody can operate a did grinder but I know there is a lot more in it than that..

What workshops would come recommended for some light head work?

[STATUS]

WOFT, dont bother... add an extra pound of boost for the same result as a 1.5k port job.... see it all the time.

[BlackBox]

Reading this is what got me excited for a head job

http://www.lewisengines.com.au/rb-tech/

Would it be worth doing anything to the head at 100,000 km?

Where else would my money be better invested then?

[scotty nm35]

A drum of ethanol and more boost.

[BlackBox]

The closest place to get ethanol is 350km away, if they don't have it then it's 800km.. I would buy it by the drum but have heard it's got very short shelf life

[GTSBoy]

More boost + WMI then.

[Piggaz]

It will be fine in a drum/jerry can.

[Ben C34]

Don't leave it on the shelf. Put it in a drum or jerry

[scotty nm35]

. I would buy it by the drum but have heard it's got very short shelf life

You heard wrong.

[BlackBox]

Apparently stored correctly in a 44 drum it would be good for 3 months max, not sure I would go through it that fast especially considering the car only comes out to leave town and It wouldn't make it to the next servo selling e85