Fitting Zoomies ??

[mgbv8]

I'm going to make some zoomies to try for a while. No room to fit these out the side though. They will come straight up through the bonnet either side of the blower. They will be wrapped up to the bonnet line and bare metal outside.

I've got some header flanges that have been cut with 2" round sections instead of oblong. So the oblong holes are in the middle of the round flanges.

This will allow up to 2" pipes to be welded straight onto the flanges, but will leave the bolt holes a bit tight so i may need to use allen bolts or just dress the pipes in a little in that area.

The flanges will be port matched to each head before welding. but this will leave an oblong hole looking into a larger round pipe. It has been suggested that this change in section could give rise to some odd exhaust flow so i should taper the pipes down to match the oblong holes in the header flanges?

I was just going to weld 2" or 1.75" elbows straight onto the flanges. Then about 20" or more of vertical pipe onto the elbows.

I have been told to make the vertical pipes too long and then go racing. I was told to put some exhaust paint on and see where the paint stops burning off after some full power runs. Then cut the pipes about an inch above this point. OR to polish the pipes and see where the blueing stops and cut about 4" above this ?

This isnt a tuned exhaust. I just want to achieve the least resistance for each cylinder and get the gasses out asap.

Any suggestions, advice or experience of the above ?

Pel

[bigaldart]

Perry,

From your flange description I would be very tempted to run a stub stack type exhaust, a short pipe matching the port, maybe 1" to 1 1/2" long with the 2" round fitting over it, this gives a great anti reversion set up, shouldn't be much reversion anyway with the blower! As far as length goes it is really a matter of taste, cut to the length you like the look of, performance wise I doubt there will be any benefit on a blown motor, if you retard timing then expect a few flashes of flame, you don't want to be startled. Another thought is where will the fuel spray go if it drops a cylinder, windscreen full of fuel could be entertaining on the big end.

Alan

[mgbv8]

Perry,

From your flange description I would be very tempted to run a stub stack type exhaust, a short pipe matching the port, maybe 1" to 1 1/2" long with the 2" round fitting over it, this gives a great anti reversion set up, shouldn't be much reversion anyway with the blower! As far as length goes it is really a matter of taste, cut to the length you like the look of, performance wise I doubt there will be any benefit on a blown motor, if you retard timing then expect a few flashes of flame, you don't want to be startled. Another thought is where will the fuel spray go if it drops a cylinder, windscreen full of fuel could be entertaining on the big end.

Alan

Cool!
What if I cut the 2" pipe elbows and taper them onto the oblong holes ?
Cylinders 7 and 8 are tight for exhaust clearance. So I will have to take a small radius 90 degree 2" bend and chop it down to fit like this on all 8 I assume. OR! use a smaller elbow off each flange and either swage it out to 2" or taper the 2" down to match the smaller elbow?

[bigaldart]

I would just dimple the elbows where you need to, just enough to clear the bolts, we use cap screws and they just clear with the pipes squeezed to a more rectangular shape at the flange.

Alan

[kiwicar]

Hi Perry
sound nice Als' stub stack idea should work well, especially with the 2" pipes, it should all breathe a treat and I bet you get flames!
Best regrads
Mike