I've had an old set of early Alpine headers sitting around. I got them
with two SII's I picked up a couple of years ago - one stripped junker,
with racing stripes, and one runner.
If you might recall, the Holbay head has larger exhaust ports than stock
Alpines. The stock Alpine port size is 1.12" (just under 1 1/8"). The
stock Holbay head has 1.21" (just over 1 3/16"). So, it's 0.09", about
3/32", different. I took my cast manifold from my SV, with 1.12", and
ground out the openings to make the transition more smooth - but,
ultimately getting back to the 1.12".
I've never paid too much attention to the old manifold until this last
weekend, I put the calipers to it. Would you believe 1.21" plus maybe a
hair more! I have no idea where this manifold actually cames from (other
than the car with the racing stripes). But, I'm sure glad to have finally
bothered to try. Of course this means back to the muffler shop to get the
headers attached to the new pipes. No complaints here.
I guess the moral of the story is two headers are better than one!
Jay
P.S. That junker with the stripes also had cut outs in the front frames
where they put in a wider radiator. I have no information about the
history of the car. It was found abandoned in a field. Oh well.
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