John:
Thank you for a very informative post.
This is a common problem on the early distributors, and your information
should be very useful to may people.
Including myself.
I had to replace the distributor in my 1970 MGB, as it was also giving
too much advance, too early. With the original twin carbs, it was not
really noticeable but when I installed a supercharger the problem was
much more obvious.
Thanks
Kelvin Dodd
> -----Original Message-----
> From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net] On
Behalf
> Of John Di Fede
> Sent: Sunday, October 16, 2005 12:44 PM
> To: MG Mail List
> Subject: Distributor advance springs
>
> 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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