Alternator changes and upgrades are among the most common underbonnet modifications performed on British cars. We’ve seen hundreds of these swaps performed through the years. While some are appropriate and effective, we’ve witnessed—and fixed—too many that have ultimately caused some sort of expensive problem: an electrical meltdown, a spinning part thrown from the car, or maybe just something sticking itself …
Sorry Carl,
Your article was good as far as it went, but a good number of post-war British cars had tcchometers that were driven from a small gearbox off the back end of the generator, and you fell short by not dealing with this issue.
The Denso is far from being an ideal alternator. Many of the small models were single wire, but more importantly, the rectifier unit, was packed around the rear of the unti, thus preventing the adaptionof the tach drive take-off.
Gord Clark
Rockburn, QC
several old MGs from '34 to '54
One in a million application Gord.
Actually, it wasn't just the 30s - 50s cars. 60s/70s Austin Healeys and the TR6 also drove the tach off the dynamo.
1. If the wiring is bad, it should be repaired wheather using a modern alternator or an old generator. If wiring is bad, repair/replace the wiring. (BTW lots of old splicing and wire butchery to add stereos and other components adds resistance and is bad). Also GM makes a great electric conduit thats easy to install and cheap. Use it wherever wire chaffing may occur.
2. Some old Britt cars have very few fuses. I had an Austin Mini with only 4 total fuses and the Jackass previous owner rewired it so only 2 worked. Add fuses as needed and check for wiring problems.
3. Lucas generators used on MGs will only put out 12 amps after going through an external regulator and old high resistance wiring. Add the amperage needed for ignition, fuel pump, radio, lights and wipers. Factor in wire resistance and you need more than 12 amps to power it all. A long night drive in the rain might kill the battery. Sounds like a modern alternator would be nice to have.
4. A properly working component, say a headlight will only draw a certain amount of amperage, say 5 amps. If the Alternator puts out 80 amps, what happens to the rest? The internal regulator of the alternator regulates as its supposed to,. No it doesnt burn up wiring.
Bottom line, if you like to drive your Britt classic, a good alternator helps. FYI the Delco 63A alternator was used in most GM cars and trucks from 69 to 85 (we know how many cars GM made then). Every junkyard has baskets of them and they are tough reliable units. I'd trust one of those before other alternators.
I have no personal experience with this product but a more original looking alternative might be a "GenerNator". It a Lucas generator body containing an alternator internals. I would be interested to hear from you or readers that have tried one.
https://gener-nator.com/
I considered one of those alternators-that-look-like-generators when I was vintage racing. The powers that be were concerned with appearances, didn't want vintage cars to look modern so ruled against obvious changes like that.
My concern was that when you are shifting just below 8,000, you can spin the guts out of a dynamo pretty quickly,. I solved my issue by finding a substitute pulley that spun the generator more slowly than normal. We had some people that thought it was worthwhile gutting the generator to slightly reduce drag and get some small undefined amount of extra power from that, but they quickly ran out of friends willing to push start them in the pits when their batteries dropped too low to start the car.
I used one of these alternators that look like a Lucas generator on our Lotus Elan project and it looks and works perfectly.
I don't understand the beneifts of a fusible link over a fuse or a circuit breaker. It appears that it would just be harder to fix in the event that something went wrong. Wouldn't something like a 30 amp automotive circuit breaker (self-resetting) be an ideal solution to put in line between the alternator and the the starter?
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