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| Cap and Rotor | Rating: 
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| Posted: 05-09-2006 07:27 pm |
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1st Post |
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Jay Member 
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I seem to have developed some spark tracking on my distributor's rotor. I also found a loose plug wire and I suspect that it contributed to the development of the tracking. My car wont even fire now, (not a single putt). I do get spark off the coil but not at the plugs. I would like to replace the cap and rotor. I see on the club warehouse the distributor (Code: 93955) and rotor (Code: 93956) are said to fit all JH and GT years "for all years Jensen Healey and Jensen GT". The Boutique list distributor Tune-Up Kits for different distributors, 23D, 25D, and 45D. Are there any differences in the caps and rotors for these distributors? My cap is different than the one pictured. The wires all come out to the side rather than out from the top and are fastened in with a sort of set screw. What should I be looking for to make sure I order the correct cap and rotor? What is the story on the style of cap with the wires to the side? Thanks, Jay
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| Posted: 05-10-2006 05:56 am |
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2nd Post |
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Mark Rosenbaum Member 
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The 23D (no vacuum) / 25D (with vacuum) series and 43D (no vacuum) / 45D (with vacuum) series use different distributor caps. I'm not sure about the other tuneup components (points, condenser, rotor). The distributor casing should have the model number cast in, but if that's not visible, then the 23D/25D has a body that tapers inward a bit as it approaches the engine, and a cap that's rounded or domed; in contrast, the 43D/45D has a basically cylindrical body and cap. I've attached a photo of a 25D distributor. Most JHs were built with 23D/25D distributors, with only some of the later cars using the 43D/45D series. I don't know of any factory documentation that indicates the time frame in which the transition occurred. The cap with wires coming from the side is an older design that dates back to the 1950s if not earlier. There's nothing wrong with this side-exit design, presuming it's made from modern plastics suitable for use in ignition systems, but in a JH, the top-exit design allows a cleaner ignition wiring layout. Some versions of the side-exit cap use screws to hold the high voltage wires in place, rather than the arrangement where the wires just plug in. Attachment: 25d4 view 4.jpg (Downloaded 70 times)
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| Posted: 05-10-2006 06:54 pm |
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3rd Post |
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Jay Member
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The number that appears on mine is 41584A (the last part is not too clear). The underside (viewed with a small mirror) appears to only have the words LUCAS and ENGLAND. I guess mine looks something like the one pictured with Mark's post (the 25D). Does mine appear to be the same too you? In the effort to look for a number I forgot to look the the vacuum advance. I think it has it on the side. Take a look at the mark on the edge of the rotor (bottom edge in photo). Is that the spark tracking area? I was also going to replace the plugs and wires and was wondering what type of plug wires would be appropriate. Attachment: JH distributor_1.jpg (Downloaded 62 times)
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| Posted: 05-10-2006 08:20 pm |
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4th Post |
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Mark Rosenbaum Member
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Distributor 41584A is a type 25D and is the correct distributor for JHs with Strombergs, from engine number 4803 to somewhere around 18900. Specifications are:It's a bit hard to tell from the photo but the curved discoloration that runs through the rivet area of the rotor appears to be some sort of high voltage arcing. The cause might be a defective carbon button in the dist. cap, foreign material inside the distributor, or a deposit of carbonized oil. IMHO the rotor and distributor cap will both need replacement. If you remove the distributor from the engine to change the points and condenser, you should also replace the o-ring on the distributor spigot (the part that is inserted into the engine). Also, remember to lubricate the rubbing block on the points or it will wear down very quickly and you'll need to readjust the points gap every few hundred miles or so. For spark plugs, everybody seems to have their own preference but NGK plugs have always worked well in my JH. For plug wires, I strongly recommend the 8mm (blue) Magnecor wire sets (usual disclaimers). My car still has the same set installed in 1999 or 2000 by its PO, and they have exhibited no problems whatsoever. If you use a good grade of dielectric grease to seal the spark plug and distributor boots, your ignition system becomes virtually waterproof. As a case in point, my car starts and runs even if the spark plug boots are submerged in residual water left over after an engine cleaning. All the parts you'll need for a tuneup are available from Delta or through the JHPS. Their prices have always been fair, and are often the lowest available, and in addition you know you'll be getting quality stuff. Again, usual disclaimers.
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| Posted: 05-12-2006 09:44 pm |
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5th Post |
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edward_davis Member 
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I was looking at John Kimbrough's website, which has a copy of the JH owner's manual (missing from my car). Anyway, that manual said that the stock distributor has a rev limiter built in, limiting the engine to <7000 rpm. I also saw something on e-bay cliaming to be a rev limiter dist rotor. Is the distributor I have on my car likely to have a rev limiter still? Also, do the cap and rotor on sale from the club store or Delta have the rev limiter? Or is the limiter somewhere else in the distributor? Thanks, Edward
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| Posted: 05-12-2006 11:41 pm |
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6th Post |
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Mark Rosenbaum Member
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There are two rotor types available, the inexpensive conventional ones and the expensive rev limiter ones. You'll find the former available most everywhere, including Delta and the JHPS. You should be able to order the latter from your local Lotus dealer or Lucas parts distributorship. I've attached a photo of the correct rev limit rotor for your persual. Operation is mechanical. The curved silvery colored arc is in electrical contact with the distributor shaft, which is electrically grounded. The central section is in electrical contact with the high voltage from the ignition coil. The central part with the two screws is held in position by springs. As engine speed increases, this part moves outward against the spring pressure until it makes contact with the raised part of the silvery ring, shorting out the high voltage. This causes the engine to quit running and begin to slow down. Eventually the engine is turning slowly enough that the spring forces the central section inward. At this time the high voltage is no longer shorted out, and the engine begins to run again. Note that all Lucas rev limiting rotors are marked with the distributor shaft speed at which they operate. This means that if you want an engine limit speed of 7000 rpm you should use a rotor marked 3500 rpm. Rotors with several other limit speeds are available There are two ways to tell what's in your distributor: (a) pop the cap and take a look, or (b) rev the engine and note the speed at which it either quits running or blows up. Needless to say, case (a) is preferable. :^} Attachment: Rotor 54424982 DRB108 3500rpm #2.jpg (Downloaded 148 times)
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| Posted: 05-12-2006 11:49 pm |
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7th Post |
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edward_davis Member
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Looks like I'll just have to use the rev limiter between my ears. Previous inspection of the rotor in my JH indicated it was the conventional one.
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