A few days ago, there was mention on the digest of the bimetallic strip
device (I'll call it the BSD from now on) on the side of late ZS carbs. This
got me thinking, as I had looked at everything else to cure the obviously
carb-related tuning problems in my ex-US TR6.
ie: Lumpy idle
Runs OK (but on the lean side) up to 3000 rpm
Runs on one carb only at high revs (also too lean as the
choke would fix it somewhat)
Over the months I have replaced diaphrapms, checked and adjusted floats,
checked needles and played endlessly with the only adjusting screw on each
carb - all to no avail.
Last night, after reading the digest reference to the BSD, I pulled of the
plastic covers and lo! one carb had the BSD fully in (closing the valve I
assume) whilst the other was half open. This seems to be caused by the strip
itself having been installed upside down in one carb! The carb with the
half-open BSD was the leaner one, so I flipped the strip to close the valve
and went for a drive - transformation! The car now idles smoothly, pulls
cleanly to 4,500 rpm, and then goes a bit flat (but this may be due to
something else completely).
Which brings me to my questions to all the learned listers out there:
1) The BSD strip has a kink just next to the Philips head mounting screw;
should the kink be oriented to push the valve into, or pull it out of the
carb body?
2) There is a miniature adjusting nyloc nut next to the mounting screw;
anybody know the rules for adjusting it?
3) The BSD is obviously a smog device, but can have a drastic effect on
performance. As we have no smog tests on old cars in Australia, is there a
fixed BSD valve position which will give best performance under all
conditions (ie: lock the valve open or closed)?
All input on this issue gratefully received.
Peter Wilson
'69 TR6 now safely downunder
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