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Hello everyone, in my quest to find a S/H distributor to keep as a spare, I have been offered a 45D.  Now I believe that these superceded the 25D in the mid '70s, and that the LT lead exited the body at a different place.  However, does anyone know what the implications are of using the later unit?  Is the advance curve the same, what about the vacuum advance etc ?  Thanks folks.  Mike.

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The type (25D/45D) is just the basic style. The advance curves are something else and will vary depending on the engine the dizzy was intended for.  There were even different advance curves for the  DM2 and 25D for the TR4 depending on the engine so it's unlikely a 45D from another car will be right:

 

dizzy.thumb.jpg.20c8878210c616e8c25d579c5f380e42.jpg

Edited by RobH
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As log as you have the one you want as a guide it's not too difficult to either swap the A/R weights and springs over or modify the weights to suit. May involve a bit of welding to increase the size of the weight if less advance is needed, or grinding if more.

Chris 

 

 

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Interesting comparison but gives a bit of a false impression if your mind defaults to "crank position" like mine does.

If you were to plot them  against crank position ie move all the curves up so that the peak occurs at 32 degrees and ignore the bit below 800 rpm tickover speed then they are more comparable.

I guess that the earlier cars are very retarded below tick over for easier starting, possibly by hand with a crank handle.

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Thank you to everyone who replied, some great technical info provided.  However, red face time......the advertiser of the 45D has just revised the info he originally provided.  Turns out the distributor in question is a 25, not a 45.  Sorry for wasting your time fellas.  Mike.

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