RB26DETT exhaust port "bulge"?

[LTSJayce]

I was at a local workshop,and noticed a bare RB26DETT head. The exhaust ports each had a "bulge" that seemed to be factory cast( I haven't seen many heads actually bare and off an engine to notice this cating thing...). The extend a reasonable way back into the head,and I'd offer an opinion that they'd take up a reasonable bit of real estate in the port,flow wise. The front three cylinders' bulge was facing,I think, rear + lower in the port,with the rear three cylinders facing forward + lower. I've heard a theory that they protect a waterjacket,but I've also heard that workshops grind them down to improve exhaust gas flow...so,no waterjacket. Are they fine on a standard engine,but removed on bigger power-up jobs? Nissan wouldn't have put these bulges there because they were bored. So;what gives?

[bmxwrx]

I think they have given undesireable effects in the past when they were removed.

[LTSJayce]

I think they have given undesireable effects in the past when they were removed.

Want to enlighten me with "undesireable effects"?

[Roy]

Cubes is the man that can answer this. I think it has something to do with trying to shape/direct the airflow for when it enters the exhaust manifolds.

Sorry, thats all i can offer

[LTSJayce]

Thanks Roy! Sooooo...Cubes? Wanna contribute? Now I'm REALLY curious what these things are...

[Cubes]

Its to help direct the flow in the stock manifold.

Remove it if you are planning on using a nice tubular manifold.

In reality there is bugger all in it.

[LTSJayce]

Its to help direct the flow in the stock manifold.

Remove it if you are planning on using a nice tubular manifold.

In reality there is bugger all in it.

Thanks,Cubes! I hoped that was the idea. I have a really nice set of HKS extractors(the ones whose model escapes me-they have the "balancer" tubes between the front and rear three cylinders)that will most likely benefit from said removal ,and subsequent matching,when my head work gets done. If I was leaving the engine as standard,I wouldn't have touched these bulge things,but with what I have planned...well,it looks like they'll probably have to go! Thanks too for the more learned of my fellow SAU'ers that've kept an eye on my inexperience via this thread and helped accordingly! Cheers guys! Jayce.

[GTRgeoff]

Jayce, hunt around and find Boosted Zeds thread on the matched and extrude honed manifolds.

[LTSJayce]

Now we're getting somewhere! Thanks all that have helped so far!