Some engines were always prone to running on of the type you describe, and
mine (73) got much worse after the demise of leaded, even with 98 octane
which is supposed to be only 1 point below what leaded was. Hot-spots in
the combustion chamber are the usual cause, and these can be due to design,
flashing left after machining, or carbon, and the higher the idle the worse
it gets. With carbon whilst removing it may help it will probably come back
quite soon. Eventually I fitted an anti-run valve system similar to the
North American factory system which has completely cured it on mine (see
http://www.mgb-stuff.org.uk/wn_fuelframe.htm and click on 'Running-on'), so
much so that I can now have it idling a bit higher than spec which prevents
a tendency to stall in a long idle, which is another common feature. Timing
depends on your engine prefix and distributor reference number, and that
varied with market, you can find curve information on the above site - click
on 'Spanners' on the left to expand it then 'Ignition' then 'Distributor
Curves'.
PaulH.
----- Original Message -----
> I have a
> little problem with my new 1970 MGB GT Automatic.. When I switch off at
> the key, it runs, chugs, pops then stops.. It's annoying and
> embarrassing and I'm sure it's not good for the engine.
|