I've been slowly stripping and re-building the ABZ going into my toy and while on the whole it looks really nicely created, quite simple and compact, I was looking at the ports and manifolds. The stock variable intake is VERY heavy (noted in an earlier post, it's about 16kg) but lines up well with the intake ports, bearly a 0.5mm lip as far as I can tell. The exhaust side also lines up well but the manifold face has 41mm holes and the ports are 39mm. However the stock "log" manifolds (certainly far from equal length and appear to be 4:3:1 within the length of the block) are welded tubes so fairly light but the welds holding the pipework to the flange are HUGE! They form a (very nice and well welded) 34mm restriction immediately after the exit from the port. I'm considering grinding this back to in line with the internal tubing diam but I'm concerned I'll a) break through and b)thin out the weld too far. I'll eventually replace with a nice set of equal length headers but in the mean time I don't think I can leave that 20% area restriction in there and sleep at night .

Has anyone ported/ground one of these back yet and has any experience they wish to share?

If you're worried about breaking through, could you just put another layer of weld on the outside first (assuming the looks aren't too critical), then grind away the inside?

Regards
Hugh

Can't get to the outside unfortunately, it's sort of "skinned" in a lightweight skin. I think the best option is to bin it but that's a bit pricey at the moment!




[Edited on 24/5/12 by coyoteboy]

On most manifolds I've seen the 'skin' is just a bit of a heat shield. I think on most cars I've had, by the time you get to 120K+ they start to rattle as the metal fatigues around the attachment points. Since I don't like the rattle I then apply Mr Cold Chisel and the rattle goes away!
Just be sure thats all it's for first, and you haven't got anything too temperature sensitive right next to it.
Regards
Hugh

In this case the skin is welded all around. Those two holes through it are tubes welded through to allow nut access. Inside the skin there's a seperate set of what appear to be hydroformed tubes with a completely different contour to the outside sections. Undoubtedly it's just a pretty/heat shield skin but it's not coming off without demolition!

In that case I'd take the 'compromise' solution - grind out some but don't try to be too gready. 34mm compare to 39 is close to 25% less area - every 1mm increase on the diameter gives ca 5% gain in area - so grind to say 37mm and be happy that you have a 15% increase!
I would just check the tube diameter beyond the weld first.
Regards
Hugh

Think the compromise might be the end result. Heres a close-up.


ABZ