At Eclectic Motorworks, we're about to update a TR7 vintage race car with a lightweight modern alternator after having it go through several "Lucas" units in the past few seasons. I put "Lucas" in quotes because most of them have been brand new Lucas copies made in Turkey or somewhere.
Many vintage racers are using compact, low output Japanese alternators. I think the common ones are 40-50 amps and designed for forklifts, tractors, etc.. They're all over eBay for pretty low prices while some of the racing suppliers sell what looks like the same thing for higher prices. We could go that route, but I thought I'd check with the hive for ideas.
Here is the criteria:
- 40-50 amps. More is okay but not needed. It seems like most "modern" alternators are 100+ amps.
- Compact, lightweight (that rules out good old GM alternators)
- V belt pulley
- Three wire so it can light a warning light if it pitches the belt or stops working.
- Able to be spun constantly at race RPM (let's say 7-12K RPM alternator speed) for 30 minute sessions without overheating or destroying bearings.
- Ideally, common and readily available at auto parts stores.
- Closer to $100 than $300.
Summit Racing sells this one:
https://www.summitracing.com/parts/tsn-es1004#overview
It seems to fit the bill except maybe for item 6. We could just buy a spare for the customer. Or is this a common alternator? We don't mind helping Summit stay in the black, but if there is another easy button someone can share, I'd appreciate it.
I really like Powermaster for alternators and starters. They're hand-built in the USA, individually tested (with data!), and use quality components (bearings, regulators, etc). I replaced the full-size Bosch AL49 on my E30 with a CS120-style Powermaster and couldn't be happier. Absolutely worth the modest price. Light, small, built for track duty, and rated for 18k RPM (check your pulley ratio). For a backup/spare, it's the same as what came on many GM trucks in the 90s (think small-cap HEI motors), so there should be one on the shelf at virtually every FLAPS in the country--though the parts store variety is certainly a lesser example. Mine is a true 1-wire but you might be able to find a variant with the light output.
Tom1200
PowerDork
3/18/25 3:44 p.m.
Hitachi LT135 from a Datsun 1200 or Hitachi LR135 from a Nissan 210.
Readily available from Rockauto; the later model has a IC regulator versus the early model using an external regulator.
They weigh 8.5lbs.
The motor in my 1200 spins to 8200rpm and the alternator has been on the car since 1985. They are that durable.
Trent
UltimaDork
3/18/25 4:18 p.m.
Take "available at auto parts stores" and replace it with "Available at yard equipment shops" and you get what you need
That Denso 35/40 amp unit was originally spec'ed for the John Deere Gator, countless Yanmar diesels and many other pieces of small landscaping equipment.
ShawnG
MegaDork
3/18/25 5:57 p.m.
In reply to Trent :
The Goldwing guys who are too lazy to pull the engine and change the stator use that unit on a bracket to solve the problem.
It's as ugly as homemade sin on a Goldwing but you can hide it on a car pretty easy.
JoeTR6
SuperDork
3/18/25 6:34 p.m.
For my TR6, I used a 1980 Ford Fiesta Bosch alternator. it uses the same 3-wire plug as the Lucas units and needs just a little shimming to bolt right in. They used to be available at FLAPS, and are still on the Internet. Weight is around 11 lbs., capacity 55 amps, and cost is $80 to $130 (Remy from RockAuto).
You might need an underdrive pulley.
Look at the models swapped onto Samurai G13-series engines, there's a 60A GM model and a Mazda equivalent. They're cheap and not hard to find. The original Samurai alternator is tiny with something like 30-40A output but quite rare now.
Edit: These might be the same GM alt you ruled out, they're not particularly huge and heavy but they're not small either. If you need small and light and you're willing to pay for it, the SxS alt above may be your best bet.
