Hello !
I am relatively new to this mailing list. Been lurking here
& on British-Car-Digest for about a month. Great reading!
I have 2 questions about carbs. With a "stock" '78 Spitfire
setup, I get backfiring on deceleration. When I disconnect
the air pump at the check valve, the backfiring goes away. There
is no diverter valve on this particular model year. I sometimes
use this same carb/manifold with a header (no provision for air pump
here) and have no backfiring. The car seems to perform fine regardless
of the configuration. I suspect the carb may be set too lean, any
WAGs on this would be appreciated.
My second question is about Webers. I have a 45 DCOE that has been
sitting on the shelf for several years. I bought the Haynes book on
Webers, tried various main and idle jets, and after lots of trial
and error, got it tweaked in somewhat. I was never able
to really get it really "drivable" however. It idled OK. It drove OK
when above 2000 RPM. There was always a "flat spot" coming off idle
though. I had to get the RPMs WAY up and slip the clutch a lot when
driving off from a standstill, or else the car might balk or stall.
My inability to overcome this problem caused me to shelve the Weber
and finally fix the original carb myself. I would really like to use
the Weber though. Local "experts" have told me.
1) Webers are just "lumpy" like that, it's a racing carb, there is
nothing I can do about it.
2) A 45DCOE is too much carb for a Spitfire 1500.
3) You have to use a performance cam w/ a 45DCOE
4) I just haven't found the magic combination of jets/tubes yet.
I'm hoping the #4 is the right answer. Does anyone know of a good
starting point jet wise? I know there are other variables to
consider and there is no universally "right" answer.
I would be using the Weber with a header and Mallory dual point,
w/ no vacuum advance. The engine is in reasonably good health.
SWAGs here would be greatly appreciated.
Bob Sykes
a BLANK in need of advice
74, 75, 78, 78 Spitfires
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