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| Joined: | 04-16-2018 |
| Location: | Santa Barbara, California USA |
| Posts: | 22 |
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answerman wrote:
No, the rebuilt Lucas has been perfect. Problem was that my original distributor, the one that came with the car, was a 45D4, not a 25D4, and Greg was pretty sure it was an MGB distributor. So, I had to scour the group for someone who had an actual JH spec 25D4 that could be rebuilt (thanks Stephen Luckett). That worked out fine once I got the correct one: I still have oil leaks to track down, but not from the distributor.Don't focus on the "25D4" as being the answer. It's the "JH spec" part that is critical. When the JH-907 came out, Lucas was making the 23D4 & 25D4 distributors. Later ('74 ??) Lucas introduced the 43D4 & 45D4, and dropped the earlier models. Which distributor your engine came with was a simple function of where it was in the timeline, and for which market it was destined (emissions or non-emissions).
Standard Lucas distributors (23/ 25/ 43/ 45) didn't have shaft seals for horizontal operation. 907 distributors were specially configured with shaft seals, and no non-9XX replacement (MG/ most Britcars) will have the seals. That includes the various aftermarket Lucas-clone distributors, like Pertronix and 123. It's unfortunate that JH/ Lotus specialists sell those modern aftermarket distributors for the 9XX... they're not appropriate as they come.
In general, the 43/45 distributors are superior to the 23/25 units. Nothing big, just evolution. One difference to notice is the size of the distributor cap. The 23/25 cap is very small, which places the plug wire terminals close together. If you run a 'hot', high performance coil (ie, 45k volts), the spark can arc between the terminals inside the small cap. For a 23/25, it's best to stick with stock coils. If you want to use "hot" coils, then it's best to install a 43/45 JH-907 distributor.
Regards,
Tim Engel
Thanks for the info, Tim.
Here is a link to a chart with a part # and description of pretty much any Lucas distributor known to man:
https://mgaguru.com/mgtech/ignition/pdf/lucas_distributor_specs.pdf
According to a chart, the distributor that came with our '74 J-H is a 41623 43D4, which is from a '78-83 Lotus Esprit/Eclat, so it should have the appropriate shaft seal. I noticed a couple of small shaft seals in the bag that I got from JAE months ago when I ordered all of the relevant seals for the distributor and the auxiliary shaft/oil pump housing, which I am sure will require distributor disassembly to replace.