Message text written by INTERNET:spamiam@comcast.net
>Yes, ZS's run fine when functioning properly, but their complexity gives
more opportunity to malfunction.
>personally, I would not say that ZS carbs are superior. Both SU and ZS
use a needle to fine tune the
>mixture and this tuning is dependent on manifold vacuum.
I think you mean venturi vacuum.
>The ZS needle is not intrinsically better than the SU's. The ZS air flow
is not intrinsically better than SU's.
>So, I would have said that with the exception of choke functions, the ZS
is not superior to SU, instead, they
>are equivalent. Since the SU is simpler, then IMHO the SU is the superior
carb!
I'm not saying they are superior, I'm saying they are different (for
emissions reasons) and thus need to be adjusted using different techniques.
The lift-the-piston method is not inherent of the system but a result of a
concious design decision that had to be abandoned for the sake of
emissions. That means that tuning techniques developed working on SU's
(and let me qualify that as pre-emissions SU's such as H6's, HS6's, HD8's
and the like) don't work on emissions compliant carbs and I think is the
source of most complaints about Strombergs. Folks who are comfortable
working on SU's apply their time proven techniques to Z-S will be
disappointed and blame the carbs.
As far as SU's being simpler I would have to argue that. The HS6's have a
monkey motion jet linkage for startup enrichment, the Stromberg has a
simple cable actuated starting device, the packing gland on the jets can A)
cause the jets to hang up and not return to the full up position or B) leak
gas on the hot exhaust manifold. The HS6 has the little hose to the jet
that can pop loose or crack and leak gas on your hot exhaust manifold. The
Stromberg has (or most anyway) have adjustable needles so the jets are
fixed and all those issues are gone. The strombergs have throttle shaft
seals so minor wear on the shaft bushings does not result in a vacuum leak
(the down side to these are they leak anyway and you have the equivalent of
an SU in this respect).
The Stromberg has a diaghram on the piston which eliminates the need for
close tolerance machining and matching of the pistons to domes. A little
over exuberance on the buffing wheel with an SU will result in a hang-up
condition (has happened). So can carbon deposition due to engine backfire.
So you don't like Strombergs. That's fine. I do. We are both entitled to
our opinions. But TR6's can and do run just dandy with Strombergs.
Dave Massey
57 TR3 (SU's that leak and suck air past the throttle shafts)
71 TR6 (Strombergs and runs Great)
80 TR8 (Strombergs and runs even better)
Check out the new British Cars Forum:
http://www.team.net/the-local/tiki-view_forum.php?forumId=8
|