Hi Gang,
Last night I finally found time to tune the carbs on my
'70 B-GT. The car has the stock twin SU HS4s so the
adjustment was straight forward. Below is the procedure
that I used and a few numbers. What I would like to know
is how these reading compare with those from your MGBs?
The carbs were just rebuilt and the mixture adjustment,
(jet position) was set to two turns down from flush with
the venturi bridge.
I loosened the clamps on the linkage so each carb
operated independently then balanced the air flow using a
UniSyn <I think it was once called> until the flow rate was
equal at 800 rpm. I revved the engine just a little using one
carb then the other noticing that the engine settled back
down to 800 rpm and that the air flow was still synched. I
then locked the linkage and set off on adjusting the mixture.
With a tachometer wired to the coil and a vacuum gauge
connected to the inlet manifold, I adjusted each jet-height
nut up and down observing changes in rpm and vacuum
until I maximized the vacuum at 16-17 in Hg with the engine
speed still at 800 rpm. The little bugger sure sounds good
now and leaps to life when the throttle is cracked open.
My question is just this; What manifold depression do
you measure on your MGBs? A wonderful old book called,
"The Sports Car Engine - Its Tuning and Maintenance" by
Colin Campbell, says that a nice healthy MGA should pull
18-19 in Hg but does not list the MGB <as the book is a
little too old>.
Best regards,
--
Rick Lindsay
Diamond Geoscience Research
5727 S. Lewis Ave., Tulsa, OK
Voice: +1 918-747-3456
Fax: +1 918-747-8599
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