as it stats just wondering if a12 extractors will bolt onto an A15 engine

I believe that they will bolt on but, I think you will find that the exhaust port in the head is larger than the extractor port. If the extractor port is smaller it would interrupt your exhaust flow, affect performance and negate the benefit that the extractors were intended to provide.
I am sure that others here will be able to definately confirm the port size issue though.

yea i agree i think that a15 have oval ports that are bigger than the a12s round ports but im not sure id were the manafold bolts on is any smaller on eather motor but i think ull have to ask some one with more experance

Just to clear clarify the oval port Vs round ports are only the inlets and not the exhaust ports. The exhaust port on both heads are squarish, but I think the a15 exhaust ports are larger squares.
Maybe someone else can confirm this ?

All of the ports vary slightly but in general are the same for all models.

I've found that they can vary in position (vertically AND horizontally by a couple of mm) slightly but nothing some mild machining can't fix.

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They'll fit no worries mate.

ive swapped extractors between different A series' without any dramas at all.

it's the intake manifolds that you need to take care with.