Jerry
I'm going to add a little more to this.
There are 2 styles of SBF distributors; an early style and a later style.
The early style has a round center section and an oil port.
The later style has a tri-lobe center section with no oil port. This
casting was introduced for the 1965 model year; probably Aug 1964.
The early style has 1 maximum mechanical advance on the cam; this style
generally wears out quickly.
The diagram in the parts manual; electrical section found @ TigerUnited,
shows an early style cam and distributor.
The later style has 2 different length slots on the cam for a possible 2
different maximum mechanical advance.
Obviously you can only use one at a time but you can change to a different
length slot or modify the length of the slot to change the advance curve.
The same holds for the Hi Po distributors.
Mechanical advance is the power side of the curve.
The vacuum advance is the economy side of the curve.
Many factors govern the total advance curve; including engine components and
compression ratios.
Ron Fraser
-----Original Message-----
From: tigers-bounces@autox.team.net [mailto:tigers-bounces@autox.team.net]
On Behalf Of Jerry & Maureen (Mo)
Sent: Sunday, July 12, 2009 4:36 PM
To: 'Mountjoy'; 'kevin beck'
Cc: 'tiger list'
Subject: Re: [Tigers] Tigers Digest, Vol 3, Issue 266
List,
All distributors have mechanical advances. Most have vacuum advance, also -
mostly for better fuel economy. Performance distributors only have
mechanical advance (289HP), because those engines don't spend much time just
cruising, where vacuum advancing gives you more total advance; thus, better
fuel economy.
The REAL difference in all these distributors (including Tigers) is the
"curve" that has been set up in that distributor for a particular engine.
There are two criteria: (1) the amount of mechanical advance in degrees
determined by the "slots" in the bottom of the distributor (Ford); and, (2)
the rate of advancement(springs).
To date, I have not found any information that specifically tells me what
the actual "curve" looks like for a given numbered distributor.
I have graphed the "curve" from the Tiger Shop Manual and found it to be
very conservative for both the 260 and 289.
I just recurved a new Pertronics distributor for the "Pay it Forward" car
(Ford 302), and there are a mind-numbing 78 different "curves" that can be
set with this distributor. The Ford is better, though. It has an infinite
number of combinations. Ha.
Jerry Christopherson
9473187
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