Hi Gary,
Maximum mechanical advance is dictated by the cam inside the distributor.
The rpm at which the advance occurs (i.e. the advance curve) is dictated by
the 2 springs.
If it is a BJ7, then he has:
- the wrong distributor, with the wrong cam
- the wrong cam fitted in his BJ7 distributor
25D6 Distributors all 'look the same'. DM6 distributors all look the same.
There are only 2 'factory' differences between any two otherwise identical
distributors - the cam and the spring tension.
You can get cams ranging from 8 - 18 degrees cam advance (ie 16 - 36 degrees
cranshaft advance). My bet is his distributor has an 18 degree (camshaft)
advance cam fitted (ie 36 degrees of crankshaft advance) - it should be a
10 - 14 degree (camshaft) advance cam fitted (ie 20 - 28 degrees of
crankshaft advance.)
He's probably got a BJ8 distributor fitted.
Tell me the numbers stamped into the distributor body - and I'll see if I
can identify it for you, and confirm the advance curve for that
distributor..
Best regards
Chris
www.myaustinhealey.com
----- Original Message -----
From: <Warthodson@aol.com>
To: <healeys@Autox.Team.Net>
Sent: Saturday, October 16, 2004 1:23 AM
Subject: distributor advance mystery
> Our club meets monthly at a member's shop & we usually try to have a tech
> session on some subject. Last month we decided to check & set the timing
> on a
> nicely restored member's BJ7. The car is basically stock, except it does
> have a
> Pertronix installed & triple SU carbs. We first set the static timing at
> 10
> degrees advanced. The car would not idle below about 900 RPM, so we
> checked the
> advance at that speed with a dial-back-to-zero timing light. It was 22
> degrees
> advanced, with the vacuum advance disconnected. We then checked the full
> advance at approx. 3800-4000 RPM. It was 54 degrees. We took it for a
> short ride &
> confirmed that it was pinging/knocking with that high of an advance. We
> then
> reset the distributor such that the full advance was about 34 degrees. At
> that
> point we ran out of time for further investigation & decided to pick it up
> where we left off next month.
> The part that does not make any sense to me is that we were getting 44
> degrees of mechanical advance (54 total -10 static = 44). I am interested
> in
> suggestions as to why we could be getting that much mechanical advance.
> What do you
> suggest we check next month?
> Thanks,
> Gary Hodson
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