To the list;
I wanted to pass along a spring a found that works well in my early MGB
distributor. The Distributor is # 40897, used on 1963-65 high compression
engines. On my dizzy the primary spring had worn out and at idle of 1,000 rpm
my advance would come on too early. At 1000 rpm, I had a total of 25 degrees
(10 static + 15 centrifugal) advance. My assessment was that the primary
spring had worn out, allowing too much early advance.
After trial and error I found a spring to replace the primary spring. It is
included with a kit made by Mr. Gasket . The kit is intended for tuning
1969-75 advance curves in a Delco GM distributor. The Kit is sold as " #927G
or #927 Adv. Curve Kit". The kit includes advance weights and three pairs of
springs, each pair having a different characteristic. Kit cost $10.59 at my
local auto parts store in their performance section.
I replaced the primary spring in my dizzy with the gold spring from the kit.
The kit instructions state that this is the "heavy" spring. My secondary
spring was not replaced as it looked ok.
Here are my results with this new spring. Using a dial back timing light with
total advance of 30 degrees (@3,000 rpm).
RPM Total Advance Degrees
(including 10 static)
600 16
700 17.5
900 19
1,500 25
2400 30
My "butt" dyno claims a much improved power curve. No more sluggish take
offs. The engine pulls strongly from a dead stop.
You may want to try this if you suspect a dizzy problem and can't find advance
springs. One word of caution. If you try this, install the new spring with
the spring loops down, otherwise the new spring will rub against the bottom of
the points mounting plate once you re-install it. (if you buy these springs
you will understand what I mean by spring loops down)
YMMV
John Di Fede
73 MGB
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