I had a clogged fuel line to the front carb that acted some what like that.
The symptom only appeared under high throttle demand (like going up a hill).
Under high throttle, the partially blocked carb would run out of fuel. There
was enough fuel getting past the clog for regular cruising. The way I found
the problem was pushing the float pins down. The tick-tick sound of the fuel
pump was much slower on the clogged carb.
Bob Donahue (Still Stuck in the '50s)
Email - firstname.lastname@example.org
Cars: 52 MGTD - #17639
71 MGB - #GHN5UB254361
Member: NEMGTR #11470
NAMGBR # 7-3336
Hoosier MGB Club
Olde Octagons of Indiana
----- Original Message -----
From: "The Roxter" <email@example.com>
To: "Richard Ewald" <firstname.lastname@example.org>
Sent: Thursday, May 29, 2008 1:43 PM
Subject: Re: [Mgs] Performace queery
> Richard Ewald wrote:
>> A problem such as this can be caused by several things. Paul
>> mentioned misfire and high voltage break down. This is a strong
>> possibility. Your B probably needs about 10-12K volts to fire the
>> plug at idle. Open the throttle and it might take up to 20K volts.
>> If your car's plug wires start firing to ground at 15K volts it will
>> run fine at idle, and low throttle openings. A large throttle opening
>> will cause the engine to misfire and no acceleration.
>> A low output from the coil could also cause this. If there is not
>> enough voltage going into the coil due to poor connections this could
>> show up. It could be a bad coil, but honestly, these are real rare.
>> Coils almost never go bad.
>> These are just some of the reasons that back in the day tune up shops
>> had O-scopes in them. About 30 seconds on a scope and I could nail
>> the problem.
>> I very seriously doubt it is a vacuum leak. As a percentage of total
>> air going into the engine a vacuum leak is greatest at idle. A vacuum
>> leak having an effect at 3500 RPM would require a huge leak, and I
>> doubt the engine would idle.
>> Stuck carb pistons could cause such an issue, but I would look at the
>> electrical stuff first.
> Another possibility would be a clogged fuel filter or weak fuel pump.
> -The Roxter
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