i live in tas ,have a worked a15 with twin deloutoes (40mm),and was told extractors and a 1.75 inch exhast was just right for back pressure ,which is what i got (i dont know if they
just had some 1.75 pipe that they were trying to get rid of though)i hope this helps.... by the way ,a mate of mine in a cheve impala can make his exhaust flame by flicking a switch but
wont tell me how ,does any one know how such a system is rigged up i think he uses a spark plug some how?????

Hi Chris - I used an ordinary elcheapo muffler. I think it cost like $40 and the 2" pipe was about the same. I've mounted mine forward of the diff (under where the back seat was). My last
A12 with twin 40's and big extractors sounded grunty with this system - but not so loud that the constabulary came looking! The induction noise wasn't drowned out either :)
Hedman Hedders make a nice muffler out of the States - $60. Most of us who buy original 1200's find that they still have most of the 28 year old pea shooter exhaust system left - mild steel
lasts OK and frees up money for go fast things!!
I'm dropping my A15 head into the machine shop tomorrow. I'm running avgas so will aim for about 11.5:1 compression. I cc'd the head today - was 30ml - and we need to plane that down to
17ml. I can let you know how things go with gaskets, pushrods etc if you're interested. Are you going to modify it or just bolt on? Is it a round or oval port head? Let me know if I can
help.

Cheers guys, I reckon that I might go with the 2 inch, Teretonga (Ian), when you said a V8 muffler, did you have any specific brand in mind? and would you recomend I mount it in the
standard place or at the back?
sweet!
The other question was do I use an A12 head gasket with the A15 head or are they both exactly the same??? And I remember reading somewhere that you need to use the push rods from
the heads engine???
Man, im stoked you guys helped thanks guys.