[Top] [All Lists]

Re: '77 MGB with Carb Problems - HELP

To: "Rich Peterson" <>, "MGS" <>
Subject: Re: '77 MGB with Carb Problems - HELP
From: "Lawrie Alexander" <>
Date: Sat, 1 May 1999 22:28:57 -0700

All the symptoms suggest excessive richness. Either the choke is not coming
off quickly enough (fault of either the way manual control is attached - or
the manual controller's technique), or a blocked passage in the carb. At the
bottom of the venturi, when you look in from the front, there is a very
small hole. If this gets plugged, the carb will run too rich. See if you can
pass a thin wire all the way down it.

British Sportscar Center
-----Original Message-----
From: Rich Peterson <>
To: MGS <>
Date: Saturday, May 01, 1999 8:20 PM
Subject: '77 MGB with Carb Problems - HELP

>My '77 B appears to have developed carb problems and I can't figure out
>what is wrong.  Background:  The car has 110,000 miles, good compression
>(130 +/- on all four), luminition electronic ignition, desmogged engine,
>original ZS carb which was rebuilt a few years ago, manual choke
>conversion, new plug wires, new NGK plugs, timing set to 15 BTDC w/o
>vacuum advance and it runs on 92+ octane gas.
>The problems I've developed are:  Bad misfire while warming up from
>cold; poor fuel economy (20 MPG); excessively rich mixture (black, sooty
>plugs); poor hot restart; idle falls to about 400 rpm when hot (fans
>I've tried to lean out the mixture, but the needle is all the way down
>and it is still running rich.  I've lowered the float level, but that
>doesn't seem to make any difference until I hit a certain point - then
>the car won't run.  I get about 18-20 inches of vacuum at idle, so I
>don't think I have a vacuum leak.  I've readjusted the manual choke
>conversion, so I don't think that it's the problem, although it's the
>most suspect at this point (i've tried swapping the choke body with
>another that I have with no change in the problems).
>Once the car reaches operating temperature, it seems to run well,
>although there is an irregular miss at idle.  It has good power and
>pulls well throughout the RPM range - I feel a definite surge as the RPM
>moves past 3000-3500 rpm under full throttle acceleration and it feels
>especially strong between 3000 and redline (gotta have some fun to ease
>the pain of my problem . . .he he).
>Any guesses?  It has me baffled.  I'd love to replace the ZS with a pair
>of SUs, but the budget (SO) won't allow it, so I must fix this problem
>with existing hardware.
>Rich P.

<Prev in Thread] Current Thread [Next in Thread>