Porting Rb26 Head On 500Whp Setup?

[scotty nm35]

I would assume no-one has ever ported the head and then re-tuned without doing other mods at the same time.

[GTSBoy]

Cross sectional area of the port at that point is seldom the limiting factor in how well an exhaust port flows. I would not concern yourself.

[zebra]

This ^ especially on a turbo engine

[MJTru]

Can you expand a bit on this subject. Cross sectional area of the poet is what im meaning.

Thanks in advance mate.

I ask because im still confused. I have just finished cleaning uo the bowls, but now im looking at the bumps in the exhaust and I can contest in saying that this hump does not seem to be there because of the exhaust studs. There is plenty of room or material for the stud. I do agree that the walls might be thin or close to the water ports.

[Piggaz]

These are photo's of my own head. Exhaust ports takes out to gasket size. Elrodeo666's head was the same . I don't have water in my turbine housings yet.

[MJTru]

Thanks piggaz. For the photos. I didnt mean that it cant work I just wanted to say that it would be closer to the water galleries. But I have heard that if people are running after market manifold that these humps need to go. Some even say its a must. But I like to look at the benefits of having it out. Exhaust flow is critical in making power.

Can you say from experience that it made a difference in power.

Or did you do it for a peace of mind. What led you up to the point where you choosed to take them out.

Thanks mate. I value your insight.

[scotty nm35]

Just clean it up, the head ports are nowhere near as bad as the stock exhaust manifold, and I have seen 430kw through it.

Remember, keeping the gas speed as high as possible is the goal for response, until you max out the port flow and limit the top end. The turbo nozzle is by far the smallest exhaust restriction, all 6 ports add up to probably 10 times the area of the nozzle.

[MJTru]

Well mate im running a 6 boost top mount manifold. Not a stock unit. So what im wondering is will it really help in power gains. At the moment the bowls are clean and have a way better transition. But now im looking at those big bumps. Please keep in mind that thw hp goal is 600hp .

[Piggaz]

Thanks piggaz. For the photos. I didnt mean that it cant work I just wanted to say that it would be closer to the water galleries. But I have heard that if people are running after market manifold that these humps need to go. Some even say its a must. But I like to look at the benefits of having it out. Exhaust flow is critical in making power.

Can you say from experience that it made a difference in power.

Or did you do it for a peace of mind. What led you up to the point where you choosed to take them out.

Thanks mate. I value your insight.

No idea if leaving them in would have changed my power/curve.

HKS/NAPREC did this head, so they must have their little "formula" that they have worked out over the years.

Some guys on here have had a few things to say about how my head was finished off but the result hasn't been half bad so it can't be all junk.

[scotty nm35]

600hp is nothing these days on ethanol, but I assume you will be on the pootrol?

[MJTru]

Yes it will be running on petrol. 600 is not much but its good for me. Lol. This motor is being placed in a gts4 with gts4 front and rear diff.

Piggaz. If you dont mind whats the power that your motor is putting out. ????

[Piggaz]

472 rwkw on -5's is peak power (6500 rpm)

375 kw at 4500 rpm

425 kw at 5000 rpm

[MJTru]

Those are some good numbers mate. I would love to see a video of it on a dyno. As you are right where I would like to be or around that area for a better word. So im now thinking harder than ever to get rid of the humps. In its simplest form it should free up better exhaust flow in my mind. But after speaking to an old head guy. He told me the same thing you are saying or did for that matter.

In short he mentioned that at the stock limits or set up. It may work better. But at higher levels of airflow it will become restrictive. He really never did say do one or the other. But he left it to me. I guess he was saying only what I know and how I choose to build the motor will dictate my reason for taking it out.

He felt me with a head ache.

[Piggaz]

It could be like the squish pad debate too.

Leave them, take one out or take both out.

It would be nice to test them all but that's just not realistic.

[Tyranus]

IF your going to leave the heads stock might aswell give it a clean up and add some valve springs in there.

[MJTru]

I just finished the clean up of the Bowl area. But still cant make my mind up on the exhaust humps.

Well, I also cleaned up each stock valves and notice that 11 of them are compromised. It sad to say that at some point in the old motors life those broken valve guides fell in the chamber and got caught up by the valves at some point.

So im looking at ferrea valves cause I was told that yhey are the only ones that build valves in standard oem sizes. Im thinking that I can grind seat or slap seat them myself and shim the lifters myself. As I have done this kind of work before. So I feel no way in doing it again.

[Happy Seal]

Those bumps are there because of the water jackets that are close to it. . .you can remove them but not too much meat. . .there are a few machinists here that have cut the heads up to see exactly how much they can take out. . .as far as power gains I haven't seen anything concrete from this mod alone. . .

[Shoota_77]

I just finished the clean up of the Bowl area. But still cant make my mind up on the exhaust humps.

Well, I also cleaned up each stock valves and notice that 11 of them are compromised. It sad to say that at some point in the old motors life those broken valve guides fell in the chamber and got caught up by the valves at some point.

So im looking at ferrea valves cause I was told that yhey are the only ones that build valves in standard oem sizes. Im thinking that I can grind seat or slap seat them myself and shim the lifters myself. As I have done this kind of work before. So I feel no way in doing it again.

Why stay standard? Perfect opportunity to whack in a set of 1mm oversized valves. You're obviously chasing every last bit of power while you're contemplating removing the exhaust humps so why not do the valves while there is a good excuse? Price wise there is very little difference. Even if you can't fit them yourself it's not going to cost that much to get them done professionally.

[luke gtr]

example.

26/30.

6 boost manifold.

china bush bearing gt42.

445rwkw @19 - 20psi

exhaust humps untouched.

not ported.

no problems so far.

[luke gtr]

the reason they would have the humps (my reasoning), is due to the heat that passes through the port.

the hump gives extra material around the exhaust manifold stud.

with the load on the manifold, then the heat I would think you run the risk of the head becoming more mailable, and letting the studs move.

thats the way I think of it.