MikeyB1 Posted July 14, 2020 Report Share Posted July 14, 2020 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 Now I believe that these superceded the 25D in the mid '70s, and that the LT lead exited the body at a different place.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. Quote Link to post Share on other sites
RobH Posted July 14, 2020 Report Share Posted July 14, 2020 (edited) 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: Edited July 14, 2020 by RobH Quote Link to post Share on other sites
Lebro Posted July 14, 2020 Report Share Posted July 14, 2020 Surprised they vary so much ! Bob. Quote Link to post Share on other sites
ChrisR-4A Posted July 15, 2020 Report Share Posted July 15, 2020 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 Quote Link to post Share on other sites
Drewmotty Posted July 15, 2020 Report Share Posted July 15, 2020 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. Quote Link to post Share on other sites
stillp Posted July 15, 2020 Report Share Posted July 15, 2020 I'm sure Martin Jay, the Distributor Doctor, could rebuild your 45D to suit your engine. Pete Quote Link to post Share on other sites
MikeyB1 Posted July 15, 2020 Author Report Share Posted July 15, 2020 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. Quote Link to post Share on other sites
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