British Motoring
Winter 2003/2004

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Publisher Information

Alternator Conversions
Modernizing generator-powered MGAs and early MGBs

Restoring For Auction
Pitfalls of buying a basket case for big-buck resale

EFI R&D
A behind-the-scenes look at the new Moss Motors MG EFI system

Cover Car: 1948 MGTC
John Barnard’s supercharged TC is a Southern California favorite

Early American MG Motorsports
Post-War success on the track drove dealership sales

Auction Update
Notable recent British sportscar sales

Blue & Bad MGA
A ’57 that blows by its VARA E/Production competition

San Diego British Car Day
One of America’s biggest Brit shows turns 24

British Value Guide
XKE Jaguar

Editorial
Reader Letters
Readers’ Cars
News
New Products
Tech Q&A
Car Mart Classifieds
Events Calendar

On The Cover:
John Barnard and his 1948 MGTC collect trophies wherever they go. For example, he took Best Early MG honors at the VARA/Moss British Extravaganza this past May, where Tom Moor took the cover photo. Terry Baker’s MGA was shot at Buttonwillow by Leonard Emanuelson.

By Jim Morton, Morton Restorations


Reliability and power output are two good reasons to convert an MGA or early MGB generator to a later-model alternator. Getting rid of the generator’s relay-type regulator infinitely improves reliability, and an alternator also weighs less while producing more amperage at lower engine speeds. The two most likely upgrades for the 22-amp MGA generator are the internally regulated Lucas 16ACR 34-amp unit or a Lucas 18ACR 43-amp alternator, both found in later-model MGBs and TR6s. The alternator upgrade is only about $25 more than the cost of replacing the original generator and regulator. The swap shown here is on an MGA, which has a Lucas 106/2 regulator. Early MGBs with RB340 regulators should theoretically convert similarly. This article assumes competency in basic wiring and soldering and the ability to verify/create good grounding
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Parts List

Moss MGB alternator assembly (PN 130-100)

Moss alternator fan (PN 130-400)

Moss alternator pulley (PN 130-380)

5/16" threaded rod x 7.5" long, stop nuts, plain nut or a new Moss bracket (PN 130-115)

5/16" or 3/8" ID square steel tubing x 6"

Fan belt: 25/64" x 36.25-36.625" (9.5-10mm x 920-930mm); Napa 25-7355 or 25-7360

35amp circuit breaker (Napa CB 6348) or 35A fuse and fuse holder

Installation Notes

Disconnect both battery cables.

Put a plastic stop nut on one end of the threaded rod, then start a plain nut after it.

Thread the rod from the front of the engine through the alternator eye, the eye on the arm of the water pump, through a 2.5625" piece of square steel tubing, and the sliding bushing at the rear of the alternator.

Cut about a 2” piece of tubing to tightly fill the gap between the rear of the bushing and the rear generator mounting bracket. Paint MG Maroon (Moss P/N 220-540) if desired.

Loosen the bolts that hold the rear bracket to the block and push the threaded rod through the tubing and bracket.

Put a stop nut on the rear of the threaded rod.

Thread a 5/16” coarse-thread bolt and lock washer through the adjustment-arm slot and into the alternator eye.

Install the new fan belt

Connect the wiring harness’s 1/4" female spade connector to the alternator’s small terminal and the 3/8” spade connector to either of the larger terminals.

Upgrade the #12 yellow output wire (20-amp) with a second #12 wire and a 30-35amp circuit breaker between the D alternator terminal and A1-A wire.

A breaker with an on/off handle allows you to “theft-proof” the car.

Remove the regulator and its cover.

Cut the three heavy wires to the vertical posts on the left side and connect to terminals A1 and A.

Cut the two small wires from terminal E on the lower right end.

Cut the tall post at the top left corner (connected to terminal F), remove the dual-relay assembly.

Cut the wiring straps between terminals F and D and other wiring straps to easily remove the remaining posts.

Use resin-core solder to connect terminals A1, A, and D with #10 wire or two parallel runs of #12 wire (or add circuit breaker as described above).

Install the modified regulator using machine bolts.

Connect NU (brown/copper) from ignition to A1, 2N (brown) from starter relay to A, YG (yellow/green) from alternator’s small post to F, large Y (yellow from either alternator’s large post) to D, small Y (dash light) to D (originally went to F), and 2B (black) ground to E.

For MGB conversion, follow above except for jumper terminals B and D on the RB340 regulator (or add circuit breaker) and move NY wire from WL to F terminal.

The system is now negative-earth/ground. Check that the ignition coil and fuel pump are connected with “+” terminal hot and “-” to ground. Some original fuel pumps aren’t polarity-sensitive, but their modern replacements might be. Also verify polarity of the radio and make sure that the “-” battery cable is now grounded to the body. On 1965-67 MGBs, the electronic tach must also be converted.