Bosch distributor advance problem

[Brett Daniels <Brett.Daniels@domain.elided>]

Hi digesti

I am still slowly working away at my 1750 and when trying to set the 
timing on the weekend with a timing light I noticed the following 
phenomenon. The manual I was using said that at about 900 rpm the 
timing marker should line up with the F point on the crank pulley and 
at higher revs it should advance to the M point (at about 4500 rpm I 
think, I don't have the book with me). On mine it seemed to advance 
with rising revs but only covered about half the distance from F to M 
as the revs rose across the prescribed range. The manual said that as 
long as the higher speed timing was OK then not to worry too much 
about the lower speed but it does seem a long way short of what I was 
expecting. I that suspect something is amiss in the advance part of 
the distributor (mechanical advance, old small Bosch distributor). 
Does anyone have any helpful suggestions, also recommendations for 
where I might find requisite parts if needed.

Thanks
--
Brett Daniels
1970 GTV

Hobart, Australia
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