On the 71, the vacuum advance goes from distributer to intake manifold. The
earlier Bs (I'm guessing 67 and older) had the vacuum connection on the
back of the rear SU carb rather than the intake manifold. Because of the
differences in location and vacuum behavior, there was also a difference in
the vacuum advance on the distributer. So in other words, your vacuum line
should go to the intake manifold.
Timing is 13 degrees BTDC at 600 rpm for the 18V engines, 12 if its the
18GK but it will be hard to eyeball the difference of one degree I think.
Check the engine number on the plate on the spark plug site. It will
probably be starting with 18GK or maybe 18V584 (late 71-2) if its around
the 71 vintage.
David
At 07:34 PM 7/15/01 -0400, you wrote:
>Hello,
>My dad and I ran a timing check on my 74 MGB and it appears that the timing
>is currently set right at TDC. The sticker on the car says to set it at 11
>degrees BTDC @ 1500 rpm. However, the engine in the car is not original. It
>is supposed to be from a 1971 B. Does that instruction still apply?
>Also, where do I hook up the vacuum advance on the distributor? Dad says
>that it's supposed to hook into a carb, but the carbs don't seem to make any
>allowance for that. These are SUs that have separate float chambers, but I
>don't know the model number. There is a plugged vacuum connection on the
>intake manifold. Is that where it's supposed to go? The websites I've looked
>at aren't conclusive on this.
>Thanks,
>Bill
>1974 MGB, 71 engine
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