Installing a GM/Delco
Alternator in your LBC
These pages document replacing the Lucas alternator
in my various LBC's. Examples here detail a MG BGT,
a MG Midget, a Triumph Spitfire, and a Triumph GT6 installation.
The "J" bracket
Special news update:
Here's a fantastic cross reference for any vehicle's
The old style Lucas unit ('73 MGBGT) and a newer GM/Delco unit
The old style Lucas unit ('75 Triumph Spitfire) and a newer GM/Delco unit
The new style GM/Delco unit ('73 MG Midget) and the old Lucas unit
The old style Lucas unit ('73 Triumph GT6) and a newer GM/Delco unit
There are a number of good web sites describing the replacement of your old Lucas alternator with a higher power GM/Delco unit. My reasons for this swap were simple. I got fed up with spending $100+ on a rebuilt Lucas unit, just to have it flake out on me in less than a year. I don't blame the Lucas units. After all they (on my cars) lasted over twenty-five years. It's the quality of the rebuilds and the parts used by the companies to rebuild them. I have no idea who makes the parts, and my intent is not to blame anyone for the lack of quality. In my case(s) it always manifested itself as an over-voltage. That is to say, I would notice it looked like I had my high beams on. Glancing at my voltmeter, I'd notice it would be pegged off the top of the scale! I can't believe I never frazzled anything, particularly the stereo. If I'd shut down and drift off to the side of the road, it would usually break back into regulation. This last time around it wouldn't. Testing showed it was putting out over 27 volts at 2krpms. Woah!
The GM/Delco units are inexpensive and available almost everywhere. When purchasing one, simply ask for a '1978 Chevy Camaro' unit, (305 small block if they ask). I bought mine over the counter at a local auto parts chain store.(Pep Boys ...East Coast of the US, ). It came supplied with the pulley and fan already mounted. All in all, The alternator cost me $34.99.(+ a $10 core charge) with a lifetime warrenty. The Mr. Gasket chromed 'J' bracket was $12.99 (hey..it's what they had in stock on the rack), and an adapter cable that fit the connector on the alternator was $3.99. Add $3.00 for a few extra nuts, bolts, and washers. So for just short of $55.00 (excluding core charge), I now have an alternator with nearly twice the power output of the original Lucas unit, at half the cost! It took me about five hours, including all the staging of photos to complete the swap on the BGT, and about 2 hours on the Spitfire, one hour on the Midget, and maybe three on the GT6.
On the BGT I was able to use the same fanbelt.
On the Spitfire the belt needs to be 1" longer.
On the Midget the belt was the original one on the car.
On the Gt6 I had to search out an exact length belt as there
was not much adjustment range (a 1088 mm belt was used)
At an idle (engine cold... @ roughly 850 rpm), with the headlights on, wipers, emergency flashers, and heater fan, the voltage output never fell below 14.1 volts. When I kicked on the fog lights it dropped to 13.5. When I cranked up my 120 watt stereo, it finally dropped to 12.7 volts. Remember, THIS WAS AT IDLE! Below 900 rpms, the Delco units appear to really act just like the Lucas units. Once you blip the revs' up over 1200, they break into regulation. The difference being, the Delco does not drop back out of regulation as easily as the Lucas unit when dropping back to idle speed. When I pull up to a stoplight, idling at roughly 600-750 rpm, the voltmeter is reading a steady 14.5-14.7 volts.
These pages document what I went through to mount the Delco unit in OBie, my 1973 MGB GT, which is my year round daily driver. Reliability was my utmost concern where OBie is concerned. Whitey, my 1975 Spitfire, was changed over for all of the same reasons listed above. My '73 MG Midget, and now my Triumph MKIII GT6.
All material copyright© Teglerizer 1996-2003
last edited 02/22/10
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