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MG MGB Technical - 45D instead of 25 dissy

I have a 45 distributor,can I use it in my 69 "B" to replace the 25 Dissy as the post is no good.
Rod

Rod,

I have a 69 as well, and swapped the 25 for a 45 a couple years back as the internals were pretty badly worn on the 25. The unit is a direct replacement -- the shaft is the same for each. It was a quick swap, and eliminated my wandering timing problems. I made the swap as I couldn't source a new 25D -- seems that they don't make the 25's any longer. One thing I've heard, though, is that the 45D curve isn't nearly as good as the 25D for our cars (someone feel free to correct me if I'm wrong here...). I'd do it though. If the old one is shot, the 45, even if it isn't quite the proer unit, should clean things up for you.

Mike
Mike Lord

Replacement bushings are listed in Moss for the 25D. Having them replaced might be cheaper than buying a new 45D
gerry masterman

Gerry. I have been playing with the 25D for the last several years. The Moss bushings have to be outside turned over most of the length before inserting, then have to be inside reamed to fit the shaft. Better choic would be to contact World Wide Auto Parts in Madison, Wisc who can supply a drop in bushing. But, this is only part of the problem. You also need to mount the distributor shaft between centers and check for run out. One shaft had .045" of run out. This means that the points were rather erratic in their operation. Best thing for Rod to do is to look at the advance curve of his 45D and see how it compares to the advance curve of his 69 spec dizzy. Paul Hunt's site should have both listed if the 45 D was ever used for the MGB. Les
Les Bengtson

A number of us have changed from a 25D unit to a performance oriented 45D such as Brit-tek's Eurospec or an Aldon modified one and have been quite happy with the change. The most important thing to check, as Les mentions, is the advance curve to ensure that it will work properly with your setup.
SteveO

The advance curve on the late model dizzy sucks. The unit overall sucks. I tossed mine in the garbage in place of a rebuilt early model 25D with pertronix electronic ignition. Best thing I could have done!

Get a rebuilt dizzy and put an electronic ignition in it. Good advance curve, and no more of that points jazz to keep fussing with. Can't go wrong.

Justin
Justin

It depends on which 45D you have. Some are replacements for earlier 25D spec distributors (meaning they have an advance curve intended to accommodate an HC engine using ported vacuum advance). However, several are not correct. As Les mentioned, pull the number off of the side of the 45D and look it up on Paul Hunt's site (the link is provided with all of Paul's postings on this BBS) or on the list on Doug Jackson's site at mbgmba.com. The be prepared to purchase another 45D with a compatible spec when it doesn't match. Also, you'll want to inspect the condition as suggested.

Barry
Barry Kindig

This thread was discussed between 05/05/2002 and 06/05/2002

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