AAZ exhaust porting

[HarryMann]

Is there normally a step-out between the exhaust ports in the head and the manifold ? There is on mine, quite a big step, so were VW up to, or have I got the wrong exhaust manifold? Thanks

[935racer]

Is there normally a step-out between the exhaust ports in the head and the manifold ? There is on mine, quite a big step, so were VW up to, or have I got the wrong exhaust manifold? Thanks

The vw ports/manifolds were designed by people concerned with space, no effeciency or much knowledge on flow. This is a normal problem you have.

[HarryMann]

Would their compromise have been that it doesn't do any great harm compared to a short sharp taper at that point. Presume there's plenty of metal there to match up if it helps. Thanks

[Baxter]

From tuning books and other things I have read I was always under the impression that a step was preferable, match porting the exhaust gave minimal, if any gains in power and a step is left to stop pressure waves travelling back up the manifold.
I have no first hand experience of this, just what I have read.
I suppose it could give some scavenging effect like a tapered stinger on a type 1 motor, the expanding gasses in an increasing diameter tube helps to scavenge the cylinder for better cylinder filling of a fresh charge.
Not having a pop, or after an arguement, just what I have read.