Andrew -
I expect the difference is the vacuum advance specs as expressed by three
numbers: 4-11-7 in the case of the 40480A and 40698 units.
Those numbers are typically stamped on the vacuum unit.
The first number is the vacuum where advance begins (in inches of mercury),
the second number is the vacuum where advance maxes out and the third
number is the maximum advance in crank degrees.
You're probably familiar with this page, but in case you're not - here is a
pretty comprehensive list of Lucas distributors with applications and
vacuum advance numbers: http://www.starchak.ca/tech/pdfs/lucas.pdf
Geo
On Thu, Aug 28, 2014 at 1:06 PM, Andrew Uprichard <auprichard@uprichard.net>
wrote:
> I have several usable distributors for the cars I am restoring, but all the
> vacuum units are shot. I see Moss lists various vacuum units depending on
> the type of distributor: is this a question of fit of is it more
> complicated than that - a match to the weights or something more intrinsic.
>
>
>
> So my question is - how important is it to match a vacuum unit to a
> particular distributor?
>
> Andrew Uprichard
>
> ** triumphs@autox.team.net **
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