I was about to pots a link to JH Aircooled since it's one of the few places
to post prices.
BUT !
The website says the company has now closed...
.. only transferred ownership a year or two ago I think.
I know Coolair used to have prices in their catalogue maybe worth aa try. Or if your going for a new case then sometimes they are ready prepared for bigger bores.
FWIW I paid JH about 150 I think for bores heads and full-flow - that might even have included a new oil pump. When the old guy ran it (from a big garden shed)he was about the
cheapest around though.
Thanks James, I thought I was being ignored there......
I've got a twin port case ready to be machined and no idea how much it will cost or where to take it.
You could try the best http://www.johnmaherracing.co.uk/machinework.htm" onclick="window.open(this.href);return false; at least you will get a price from a reputable engine builder to use as a guide.