[TR] TR4 Distributors

[spamiam at comcast.net]

John,

First, do a vacuum check on the vacuum capsule of each distributor.  If one leaks, then it is probably not eligible for use.  It is possible to get them serviced or (in some cases) new ones.  Also check each one for wear on the shaft and proper motion of the mechanical advance and vacuum advance mechanisms.

I have seen on EBay, some new distributors, but they appear to be a "one size fits all" approach.  

There IS a difference between the DM2 and 25D4.  Functionally, the difference is the advance curves.  How much mechanical advance, and how much vacuum advance.  I forget the specifics on these distributors, but as I recall the 25D was set up for more advance. 

More advance means more power (within limits) as long as the octane of the fuel and compression of engine can tolerate it.  The 25D4 is the later distributor, and that one would be the one I would pick if all else is equal regarding wear in the units.

Mechanically, there are differences between the DM2 and 25D4 units,  This means that the Pertronix magnet sleeve that is correct (size/orientation) for one is not right for the other.  Even then there was variability in production tolerances.  The Pertronics for my 25D4 did NOT have a snug fit on the shaft and wiggled probably 3 degrees in either direction.  Tech Service told me how to improve that, but it was definitely a Rube Goldberg fix.

>From: John Dunham <john.dunham at amphenol-tcs.com>
>Subject: [TR] TR4 Distributors
>To: "triumphs at autox.team.net" <triumphs at autox.team.net>
>Cc: triumphs at autox.team.net
>Message-ID:
>	
><OF2CE04FA4.B591314C-ON85257316.004FFC28->85257316.00505660 at amphenol-tcs.com>
>	
>Content-Type: text/plain; charset=US-ASCII
>
>As things slowly chug along on my TR4 resto, I find myself with 2
>distributors to pick from.  I have a DM2 and 25D.  I plan on going to
>negative ground & using a Pertronix, but it looks like Pertronix has a
>different kit for each distributor.  I am wondering if there are any
>inherent differences between the 2 distributors, or if one is any better
>than the other.
>Thanks in advance (no pun intended)
>John Dunham
>Development Engineering
>Amphenol TCS - A Division of Amphenol Corporation
>44 Simon Street
>Nashua, NH 03060
>Phone: 603-879-3181
>Fax: 603-879-2181
>john.dunham at amphenol-tcs.