Porting Rb26 Head On 500Whp Setup?

[cobrAA]

So yeah...I need to give my answer to my machinist tomorrow morning so I searched around and couldn't find any REAL WORLD info. only some flow bench result and such. so Have anyone seen true before and after dyno graph? to which point is porting worth it? for 1000$ what will I gain?

I only know 2 persons who did porting on their head and it's gtr-dad and mitch32. I spoke with Mitch32 he went straight to porting so he never had a before dyno graph, don't know for gtr-dad.

My machinist swear by porting but I mean.. that's his job, he won,t tell me it's worthless LOL.

I'm sure it's a nice mods but is the head of a RB26 already maxing at 500whp ? isn't more something you do when your at 650+ ?

[The Dan]

500 hp is easy on stock head

You can make it on lower boost with a WELL ported head though

[R31Nismoid]

Most heads have a minor tidy up. Seems to be all you need really.

You still going Garrett -9s? If so its a tough ask to be able to say it's worth it dropping 1k on porting.

You'd benefit more IMO from spending the money on just a solid reco on the head so that it's all in fresh order and won't give you issues later, is reliable and set for many years.

[The Dan]

No he can't be using -9's for 500whp. They are only good for 400whp.

[R31Nismoid]

He is in the US, they work differently

I just can't remember his latest decision, each thread it changes

[R31Nismoid]

He would make 450whp though no drama.

[dorifticon]

I looked at this in a fair bit of detail when I was building my rb26/30.

My findings (which were reflected in my build) were:

-It is possible that cleaning up the heads - especially the exhaust ports - may help. Some advocated removing the "humps" in the exhaust ports (look at the head, you'll see what I mean).

-However, the vast majority of people I spoke to advised against actually changing the shape of the chambers or runners, preferring velocity to outright flow capacity.

-In my view the tolerances on the head are pretty good in terms of port matching, but you can get a better match by using the gasket and light work on the head, and also the plenum connector and the exhaust manifold.

-In terms of paying money for someone to actually shape the ports, I was advised that it would be preferable to spend the dollars on oversized valves (assuming the cams and cam train is being done anyway).

In any event, I ended up finding a new head that was being sold from an abandoned build, which had 272/10.5mm cams and springs, buckets etc together with a cleaned up head and standard, re-ground valves (new ones where required).

In the end, it flowed enough for 380rwkw, which is slightly more than 500 hp. And being only "cleaned up" rather than ported as such, it doesn't induce lag or anything.

In summary, I'd say don't take the risk with porting for a 500hp setup, unless you are super confident the guy can improve over the factory head (I'd be wanting dyno graphs etc).

[Beer Baron]

yeah it can be a bit hit and miss. my advise with messing with heads is less is more.... especially if you don't really know what you are doing.

on a 26 head from my experience.

no need to go overboard enlarging inlet or exhaust ports. you want velocity. but some work is good.

be careful what you do with the squish pads. altering them drastically changes engine behaviour.

there are very good gains to be had in the short turn radius, again provided you know what you are doing.

CC'ing the chambers so they are equal is also of benefit as is removing casting marks, dags etc that can cause hot spots.

exhaust hump removal is a tricky one. it's there because of the hump created in the water jacket by the exhaust studs. removing too much means a very thin wall left...

[levinboy]

No he can't be using -9's for 500whp. They are only good for 400whp.

Im running -9s comfortably at 450awhp

[The Dan]

Im running -9s comfortably at 450awhp

Yeah I'm not saying you can't make more than 400hp at the wheels with that turbo but if you're going to tell me your RB26 is standard bore and stroke, runs on 98 and under 22psi of boost, then I would say you are wrong. You can, however, make 450rwhp UNCOMFORTABLY if you want to pump in 30psi of boost and water meth injection or 30% meth or E85 etc.

-9's are smaller than -7's and you can only ever expect 400rwhp out of -7's. Sure a little more can be had but usually that will be related to the fuel being used.

[R31Nismoid]

-9s are bigger than -7s Dan.

-7s are the same size as R34 N1.

-9s are GT-SS equiv, larger than R34 N1

[The Dan]

-9s are bigger than -7s Dan.

-7s are the same size as R34 N1.

-9s are GT-SS equiv, larger than R34 N1

Incorrect

The 707160-7 has a 44.5mm inducer and 60mm exducer on the comp and the same 53.9mm turbine that all the 2860R turbo's share

The 707160-9 has a 44.5mm inducer but only a 59.4mm exducer on the comp wheel.....smaller

[R31Nismoid]

Ye i know the exd is slightly smaller... but...

-7 is a 55 trim

-9 is a 56 trim

Slight difference, higher trim = more flow.

Garrett even make note on their website that the -7 is a N1 OEM Replacement.

I've never seen -7s make more tha 300-310rwkw, where every -9/GT-SS car makes just that bit more 310-330rwkw on average.

[R31Nismoid]

Either way it really is a poofteenth. The -7 is slightly more responsive too

Its funny too cause the maps garrett supplied are so different it doesnt even seen logical.

[The Dan]

Ye i know the exd is slightly smaller... but...

-7 is a 55 trim

-9 is a 56 trim

Slight difference, higher trim = more flow.

Garrett even make note on their website that the -7 is a N1 OEM Replacement.

I've never seen -7s make more tha 300-310rwkw, where every -9 car makes just that bit more 310-330rwkw on average.

Yeah you're right, the higher trim will have a higher flow. I just can't see 450awhp comfortably....neck ringing yes maybe......DEFINITELY NOT a 500hp setup

[R31Nismoid]

Ye nowhere near 500 lol

[rob82]

Either way it really is a poofteenth. The -7 is slightly more responsive too

Its funny too cause the maps garrett supplied are so different it doesnt even seen logical.

Max flow is around 22psi for both turbo's @ around 31 lh/min the difference is the -9's are slightly more efficient.

[marksuxass]

Few things can be done to the head for your power output.

- Leave the squish area as is.

- Clean up inlet ports with 80grit, and knife edge the splitter. (remeber just to clean up and not take away mass amounts of metal).

- Smooth out pockets inlets/exhaust (you will feel a sharp edge that pretty much extends around the whole valve seat)

- Remove the exhaust bumps and polish exhaust ports.

The main key here is to not take away too much material, and just clean up the ports.

I ended up doing this to my build myself as this was requested to be done by my tuner, purchased a head porting kit and went away with it with guidence from my tuner. Running -5's on a forged rb26. Tunner says it will crack the 500hp mark no problemo's but we will see.

[MrStabby]

Max flow is around 22psi for both turbo's @ around 31 lh/min the difference is the -9's are slightly more efficient.

Sorry for the hijack, but does that mean that anything over 22psi will just add heat and therefore there's never any reason to run more than 22?

Also, is there diminishing returns just before 22, so while 18->20 might give you a decent increase, 20->22 will give you much less?

Im running 17psi on -7s, and wondering how much further its worth pushing them.

[rob82]

Sorry for the hijack, but does that mean that anything over 22psi will just add heat and therefore there's never any reason to run more than 22?

Also, is there diminishing returns just before 22, so while 18->20 might give you a decent increase, 20->22 will give you much less?

Im running 17psi on -7s, and wondering how much further its worth pushing them.

ACtually in reading the compressor map the -7's have no more to give over 20psi of boost. But it will also depend a little on setup.

Edited June 29, 2011 by rob82