~ The mixture is rather rich at the moment... I also took the B to one of them
'computer tuneup
~ places' and the chap there stuck this probe in the exhaust to measure what
was coming out and
~ he showed me that there were 1500 parts of unburnt fuel in a million. He also
said it should
~ be more like 200 parts in a million. Dunno how much this is true, for this
type of car etc...
I seem to remember getting more like 1000 ppm when I was running rich,
but that was years ago. Have you got a Colortune? Or do the carbs have
the lifting pin?
~ > Third: Have you recently refilled the cooling system?
~ Yes, I drained it a couple of weeks ago, and filled it with Castrol
coolant/rust inhibitor
~ with a ratio of 30/70, so I'd better increase the ratio when I get home this
evening.
That can't hurt; the more water, the better for cooling.
~ Mine is a 67 mark 1.
Great car! '67 is *the* most desirable year, of course, as it's the
last year before smog and that awful dashboard. I've fixed the motor
('65 head) but I've still got the dash without the glovebox.
~ One mechanic who works only on MG's said that the I should also check the
compression and that
~ 150lbs or less I should be ok. 150-170 would cause some run-on, but can be
fixed .. 170lbs +
~ would definitely cause runon.. How does this affect the above ??
Compression creates heat -- that's how a high-compression engine gets
more power. What makes your car run on after you shut down is that
the cylinders are compressing the air-fuel mixture enough that, in
the presence of some residual heat somewhere in the cylinder, the
gasoline ignites, at least partially.
Carbon deposits in the cylinder head can not only increase the
effective compression ratio, they can also retain heat that can
push the whole thing over the edge and ignite. The only sure
way to get rid of carbon deposits is to pull the head and remove
the deposits with a wire brush and a scraper, but that's kind of
extreme. Try messing with the cooling system and the ignition
first, and of course use high-octane fuel; octane rating indicates
the fuel's tendency to pre-ignite, which is what's happening here.
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