> It's a 78 MGB with a Weber carb. The engine has been successfully
> rebuilt,
> as well as the carb (a more knowledgeable than I buddy helped me out)
> and it
> runs beautifully when sitting there. But when accelerating heavily it
> will
> begin to spit and sputter something terrible around 3-3.5k rpms and will
> continue to do so unless you push in the clutch and let it clear, at
> which
> point it will do OK. During moderate acceleration it does much better.
> I
> fooled with both the timing and the air/fuel mixture until I'm blue in
> the
> face and I can't seem to solve the problem (even the aforementioned
> buddy of
> mine gave up).
Hi Ernest!
Here is my two cents:
Carburetor:
The carb fuel air ratio adjustment only applies for the idling. So
fiddling with that will not affect your WOT performance. The carb could
either have problems with the accelerator pump (which is supposed to dump
in extra gas when you accelerate heaviely) or with the float level. If the
float level is set too low you will 'burn' all gas that is in the bowl too
fast and it might have trouble to reflow enough. Take the carburetor apart
and check the float level setting and the accelerator pump diaphragm /
mechanism. During your rebuild, I hope you have dipped the carb in a carb
cleaner bucket (best is more than 24 hours) to dissolve all old gunk? I
hope you have taken it apart as far as you could and blown all passages
through with hot water and compressed air after getting it out of the
solvent?
Vacuum:
Are you sure you don't have any vacuum leaks on the intake to head
interface or on the carb to intake interface? You can spray carb cleaner
or other solvent in the suspicious spots while car is in idlde. When idle
rpm goes up you have a vacuum leak. Fix it with new gasket(s). Another way
to check (not as well working IMHO) is to put your hands over the carb and
if it keeps on running 'too long' it might have a vacuum leak too. The
weber conversion seems to be a vacuum leak candidate on the head to intake
manifold. It is recommended that you level the alu intake and the cast
exhaust manifold with a grinder / dremel, so the thick washers that hold
it both in place can put even force on your manifolds.
Ignition:
Are you sure your ignition (points?) is set up right? Have you gapped the
points to the correct (15 thousands?) setting? Is your coil healthy and
are your sparkplugs new and gapped right? A motor with a lame spark gets
problems when the mixture to ignite gets 'thicker' under load...
Hope this gives you enough to check for now. :)
George
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