Replacing 25D with 45D dizzy

Hi all,

My vacuum advance has been split for a year now, and so far i have managed to survive by blocking off the vac connection on the rear carb. It all runs really well so i'm not too concerned, however i am looking into either replacing the vac unit within the existing 25D dizzy or replacing with a new 45D type.
My question is, is it a straight swap to fit the 45D type instead of the 25D and would it affect the running at all. I am happy to set the timing etc but what about the ignition curve, does this vary between the two type of distributor.

thanks, Carl

1974 chrome bumper
HIF Carbs

They'll swap one-for-one with no problems. My original 25D was bolixed - bad vacuum unit, as a matter of fact - and I replaced it with a 45d while I had the original repaired and recurved. I went back with the 25d primarily because I like the little thumb wheel for find-tuning (I like to play) but there was no need to do that.

The 45D just drops right in.

Yes, the ignition curve and the vacuum advance rate/amount will be very different between a 25D and a 45D. The 45D is a drop-in replacement, but the specs may or may not work for your application.

(I should add: Jeff is the one who fixed the original 25D. :thumbup: )

call roger parker of Jonathan Kimber at the MGOC (just up the M11 from you) they can tell you the advantages of the up dated Dist. I have a 45D electronic ignition....great

Thanks for the info, i think i'll drop in a 45D then as it won't cost much more than the cost of a new vac unit for the 25D.
I've been to the MGOC (and MGB Hive) just to have a look around, both were very exciting, good idea to give them a call. Sometimes you don't think of the obvious until someone mentions it !!!