Lucas to GM/Delco Alternator Swap
The lower mount 'J' bracket
On a BGT, the stock Lucas/BMC alternator mount plate will not work for the Delco unit. you need to acquire one of the aftermarket 'J' shaped brackets 'off-the-shelf' at any performance speed shop or auto parts store. The J shape is required because of the mounting ear locations on the alternator, where the original adjustment flange mount point is on the engine, and clearance issues between the alternator fan and the bracket. Some people will custom fabricate a bracket and mount it straight down to the engine mount sitting directly below the alternator. I looked at this alternative, but it seemed like I'd have to do more custom work to fit stuff which I didn't want to have to mess with.
The J bracket I used is identified here. This is a shot of the top of the package as it hangs on the wall at the parts store. ...and a shot of the un-adulterated bracket.
The two grease spots... are my 'cut-to-fit' way of measuring stuff. These dimensions are not critical. Use your own judgement.
Hey, if you're contemplating this conversion yourself, you must consider yourself somewhat handy with tools. Form fit and function are up to you.
After test mounting the Delco in place with one upper bolt, I held the bracket in place, and simply smeared my greasy finger across the chrome to mark where I wanted to cut it off, and where I thought the bolt hole needed to be drilled. You'll need to cut it in half, before you can accurately guesstimate the drill hole. The water pump pulleys don't let you swing the bracket up into place to precisely mark the stud/bolt hole.
I cut the bracket with one of those little graphite cut-off wheels on my Dremel tool. I'm sure a hacksaw would work just fine as well. You need to cut down the length, before you can accurately go back in and measure where to drill a mount hole for the original mount/pivot bolt on the engine.
CRITICAL POINT! I do believe this is about the only touchy part of the whole installation. When you drill the hole for the stud that mounts the bracket to the front of the motor, you need to drill it slightly off-center towards the inside of the J. As you'll see later, the clearance of the fan and bracket don't leave you much room for error. Half a drill bit diameter should be more than enough.
Now came a part, I guess I paid for.... by flipping the Alternator top for bottom.
The wide mount flange on the Delco Alternator, that will connect to this bracket, will clearance fit a 3/8" (.375") bolt. I would have had to insert a tube or spacer of some kind into this hole to stay with the same diameter bolts that fit the top mounts or the bolt/hole fit would have been really sloppy. So I opted for a 3" long 3/8" bolt with two flat washers and lock washer and nut as my bottom mount bolt.
The problem is the bracket I bought wouldn't let me pass the 3/8" bolt through it! So out came the hand file. I guess I could have just chucked a 3/8" drill bit into my hand drill and reamed out the 1" long area I believed would give me the adjustment range I needed.
J bracket viewed from underneath
Jumping a little ahead... here's what the bracket installed looks like from underneath. As you can see, the clearance between the fan and bracket is less than 1/8". If I had used the thinner bolt, the free play might have allowed the fan to hit the bracket.
One thing left I really don't have any good pictures of...is the little bracket added to the rear end of the Delco alternator, that connects it to the original engine mounted rear Lucas mount. The Delco unit has a small bolt in the back the I ran a small strap over to the back mount to add rigidity to the whole assembly after having adjusted the fanbelt. I simply place a small piece of metal in place, marked it and drilled it. You can see it in the first 'before/after' photo on the main page of this site.
The upper adjustable, and lower fixed mounts of the
Spitfire engine with the original Lucas unit removed
Due to the 12 and 6 o'clock positions of the mount ears on the Delco unit, the upper mount needed to be extended. The offset bend in the stock Spitfire flange was needed to properly meet the Delco top ear. But it isn't long enough. So I used the leftover MG lower adjusting bracket to simply extend the original Spitfire mount. I used two bolts in the adjustment slots, and the threaded bolt in the alternator, through the single hole in the bracket. I don't think it wise though to ever use this arrangement (original bracket with the loop in it) as a lift point to pull the engine in the future. I'll probably go with a modified 'J' bracket like on the BGT on top at some future date, but for now it's just fine.
...update... CHROME J-BRACKET HAS BEEN BENT AS NEEDED .....
...stay tuned... the '73 Midget will be included here shortly ....
A Swap to still be completed will be Lil' Greenee, my '73 MG Midget