Message text written by INTERNET:emanteno@comcast.net
>Dennis was/is somewhat correct. The fuel flow, as measured on a flow
bench, was greater in the Strombergs (pre-emissions) than the SU HS-6's.
This was researched and checked out when a certain vintage race TR4
switched from Strombergs to SU's and had less straight line top speed, and
was running higher than desired exhaust gas temperatures at wide open
throttle. No amount of richening would cure this in the SU's. Finally, the
racer (Uncle Jack) drilled out the jets in the SU's to a slight oversize,
and the problem was solved. BTW, when running Strombergs, many racers
resorted to SU needles and made shims to hold them in place, as there were
so many more tuning options with the SU needles than were available for the
Strombergs.
<
There are criteria that are more important in racing than in street
driving. Another example is the fact that the SU's have a deeper fuel bowl
and is less prone to fuel starvation in hard corners.
But lets get back to the initial problem: a stock 74 TR6 that had a problem
with the idle speed wandring and the fact that lifting the piston caused
the speed to drop. The first problem I suspect is the over-run valves and
the other is due to the fact that lifting the piston is not the proper way
to check mixture adjustment on a 74 emsisions compliant car. (also bear in
mind that he said it ran strong at all speeds)
I'd say he's real close to having it tuned just fine.
Dave
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