Cooper S distributors

[YORKY]

What are the differences between Lucas 40819, 40819A, and 40819H ? I have a 40819H dated March 1966.

Cheers Jim

[timmy201]

There would have been a slight revision with each letter suffix (of course the fuel and engines have changed in the last 60 years and distributors are worn out, so these are only what they used when brand new)

This is 40819B from the 1968 manual AKD4935

40819b.jpeg

40819A is listed as the following (in crankshaft degrees timed at TDC for comparison):
No advance under 450rpm
600rpm = 1.5 degrees
1600rpm = 12 degrees
7600rpm = 30 degrees

[BAD942B]

moving along a bit, did ST sell a new distributor cam for modified competition engines, just pulled the baseplate out of mine & there is a cam in it that is much longer toe than 15°, possibly giving just 10° or less, so 20° or less crank which makes sense, with 12° or so at idle then 32° at 7000 no markings on it at all

[Toby]

What are the differences between Lucas 40819, 40819A, and 40819H ? I have a 40819H dated March 1966.

The main difference were slight improvements to it, but not with regards to the advance on it. The biggest difference to the later ons is the O ring on the shaft where it sits in the block to prevent it foricing oil up through the distributor mounting.

[Toby]

moving along a bit, did ST sell a new distributor cam for modified competition engines, just pulled the baseplate out of mine & there is a cam in it that is much longer toe than 15°, possibly giving just 10° or less, so 20° or less crank which makes sense, with 12° or so at idle then 32° at 7000 no markings on it at all

You mean the 40979, I have one of those too. Would have to check and see which internals it has. Lucas however lists it as:

RPM1 3800 advance 15deg, RPM2 800 advance 9deg, RPM3 300 advance 1.5deg, no advance below 225

[YORKY]

Thanks for the replies.

Jim

[BAD942B]

moving along a bit, did ST sell a new distributor cam for modified competition engines, just pulled the baseplate out of mine & there is a cam in it that is much longer toe than 15°, possibly giving just 10° or less, so 20° or less crank which makes sense, with 12° or so at idle then 32° at 7000 no markings on it at all

Distributor has gone off to Distributor Doctor as our distributor machine is broken, will get specs when it comes back from reconditioning & post them up, its the original 64 distributor modified by the PO, presumably in the early 70s

[Toby]

Distributor has gone off to Distributor Doctor as our distributor machine is broken, will get specs when it comes back from reconditioning & post them up, its the original 64 distributor modified by the PO, presumably in the early 70s

Martin does do a great job on reconditioning them. I guess you discussed it with him? As he'll normally put them back to the original spec

[Peter Laidler]

I like the idea of reverting to original spec after a rebuild as a good sound engineering principle. That's because you have a known and recorded start point for anything you do thereafter. Abd you can always go back to the known square one to start again - if necessary.

[BAD942B]

Distributor has gone off to Distributor Doctor as our distributor machine is broken, will get specs when it comes back from reconditioning & post them up, its the original 64 distributor modified by the PO, presumably in the early 70s

Martin does do a great job on reconditioning them. I guess you discussed it with him? As he'll normally put them back to the original spec

Hopefully not, I have asked him to rebuild it as it was otherwise they (i have asked him to rebuild another 25D with the same curve as my original S 40819 but with vacuum advance fitted as someone suggested on this forum some time ago) will have to be altered when we run the engine on the dyno, it had about 105bhp when I rebuilt the engine in 1981, it had posssibly more with the PO who had it on a 45DCOE, the same 649 cam that I had with a C-AEG163 head which I still have sat on the shelf, LCB & side exit open exhaust

[BAD942B]

Distributor has gone off to Distributor Doctor as our distributor machine is broken, will get specs when it comes back from reconditioning & post them up, its the original 64 distributor modified by the PO, presumably in the early 70s

Martin does do a great job on reconditioning them. I guess you discussed it with him? As he'll normally put them back to the original spec

Distributor doctor rebuilt my original S distributor & another dizzy modified to S spec but with a vacuum advance, both were reset to STD S spec but with just 10° of dizzy advance instead of 15° but he took little notice of my note to check the settings on the original modified one and replicate.
Will have to set them up on Chris Conoley's Mass dyno