Lynn,
I've got twin d/draught Zeniths on my 1592 Series 3 (it came with them
originally). I've been through the 'restore or replace' loop, so here's
my 2-bob worth:
* Parts are very hard to find for them. Overhaul kits are available new,
but virtually no other parts are. Tom W. (on the alpines list) has some
used bits for them.
* Using them on the larger 1725cc engine would mean that you might be
limiting the output of the bigger motor by using carbs set up for a
smaller engine, BUT - the Zeniths came in lots of different
specifications, so you could set them up to breathe better and deliver
more fuel IF you can find the bits.
* The 'biggest' Zeniths used on an Alpine were the S2 Alpine, or
Harrington LeMans spec ones. Later Alpines (ie S3) had more restrictive
carbs to try to improve fuel economy.
* The throttle shafts get sloppy over time resulting in uneven/high idle
speeds, and flat spots. The body of the carb can have bushes pressed
into it to fix this problem. This is usually done during rebuild.
* I ended up going with a set of S2 Alpine carbs (thanks to Tom W!),
having them rebuilt and bushed. I stayed with the Zeniths to keep that
period look, and went with the S2 carbs to get more power.
* The WIP spec Zeniths use a little more fuel but are simpler and more
reliable. The WIA is the alternative spec, which has a rubber diaghram
that operates a 'power valve' under vacuum. The diaghram slpits, it's
subject to vacuum leaks, and it only saves a little fuel. I had WIAs, I
now have WIPs.
* Other carb choices: twin single downdraught Webers off a VW (fit on
early Alpine manifold, not seen it, but someone on the list has done
it); Twin barrel Weber on S4 manifold (good power, fuel econ, reliable,
but not period at all); twin Strombergs on S5 manifold (Strombergs need
as much maintenance as the d/d Zeniths, correct for S5); twin DCOE
Webers on Harrington (copy) manifold (yumm!, but big $$$, hard to set up
and keep in tune)
As always, I stand to be corrected. For a motor mechanic, I make a good
computer guy.
Hope this helps,
Cheers,
Paul.
1963 S3 ST
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