I doubt this is the issue, but one issue that Jack had was a little
piece of rubber from where the jet tube comes into the float bowl -
it allowed enough fuel to get through that it ran but would
occasionally block the jet causing the car to run like crap. Took
over 5 carb disassemblies before it was found. Different symptoms to
what you are having, though.
If you have a fuel pressure gauge and EGT gauge (front and rear), you
can tell whether it's going rich or lean.
We fought issues with fuel pressure regulators (goes lean at end of
long straight - pulling back on the gas pedal helps) and with
vibration causing the fuel in the carb bowl to foam (goes rich -
nothing you do with the gas pedal helps much), as well as the
orientation of the top of the float bowl (one goes rich - keep the
revs way up and the problem lessens as you clear the extra fuel more quickly).
With the resonance deal foaming the fuel, it seemed that once it got
started it would continue but if you could eke through the RPM that
caused the issue the resonance would stop. It wouldn't always
happen, though. This is a possibility, although what you described
as trying for the workarounds should have taken care of this issue.
Assuming that it is fuel related, it's a good idea to take the carbs
apart and make sure everything is completely clean - no dirt in the
bowl or lines.
Tony
At 05:24 PM 5/25/2011, Duncan Charlton wrote:
>I'm getting some well-thought out suggestions. Thanks to Michael P, Bob K,
>Tim M, Jim G, Tony (TR4 Tony), Russ M, Irv K, Scott B, Chris, and Bill B.
>
>My thoughts that it was fuel related seem to be supported by the fact that
>most of you mentioned fuel issues. So far:
>1. Bowl vents clear? Hmm -- we do have mud dauber wasps around here!
>2. Fuel foaming due to vibration? (X2) Possible, and perhaps the new manifold
>brace could add more vibration.
>3. Sticky float or float needles?
>4. Leaky floats?
>5. Resonance due to new brace causing jets to sink down? (They're supported by
>a spring, but it makes sense that resonance could cause the spring to lose
>tension temporarily, the way a spring governor on a lawnmower engine does)
>6. Needle(s) not properly seated in piston(s)?
>7. Advance profile poor or advance mechanism sticking?
>8. Loose engine ground cable?
>9. Improper jetting for driving style? (Perhaps, but this didn't happen at
>TWS and seemed to get progressively worse at ECR even as I tried to prevent
>the problem by braking later and sometimes holding throttle pressure while
>braking)
>10. Bowl lids (ie: float hinge point) oriented improperly)? No -- this one
>has been checked. The suggestion came from someone who was also asking
>whether it happened more when turning one direction and not another --
>direction did not matter.
>11. Dirt in carb? (X2) Fuel filter was clear when checked on Saturday but I
>haven't looked in the float bowls yet. I'll blow the lines back to the fuel
>cell (no rust seen in fuel cell when I cleaned it out a few months ago --
>found silicone worm scraps, though)
>12. Oiling plugs?
>13. Intake tract leak?
>
>The suggestions will guide my investigation -- thanks, everyone!
>
>Duncan
>'52 Morgan red #6
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