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GM (AC-DELCO) Alternator Conversion into '71 MGB
SUMMARY:
- Cheap, reliable 63-amp Delco replaces faithful (but
anemic: 34-amp) Lucas 16ACR
NOTICE!!.......This installation worked well on my '71 GT. No guarantee it will work on yours! My car has the water outlet elbow (thermostat housing) with the mounting lug for a smog pump, but NO smog pump. This may be why the larger Delco could fit. Take a careful look at your engine, and perhaps pick up a scrap alternator of the type you want to convert to, and try a test fit, to be sure the conversion is feasible without a lot of hacking. The lower alternator mount was bolted to the right engine mounting, which on my car has two studs protruding upward from the rubber sandwich. Later cars with the round, single bolt engine mounts will require something different. Alternative: read the Triumph web site to see the article on using a "Ford Fiesta" Bosch 55amp unit which apparently has identical mounting brackets as the Lucas, and which would thus be a very easy fit.
The alternator I used was an AC/Delco (GM's electrical parts subsidiary, formerly called "Delco-Remy") unit from the early 70's to mid 80's called the "10 SI". These were supplied as standard on nearly everything I've seen in junkyards from Buick station wagons to Chevettes of the period. Their rated output is 63amps, with about 23amps available at 1600 alternator RPM. There are literally millions of them out there and very cheap at rebuilders, IF you get a commonly available "clocking". I got one with a one-year warranty for $65 plus $5 'core' charge. Doing this conversion presents a great opportunity to go through the "heavy-duty" part of your B's electrical system and make sure everything is shipshape. Check the integrity of insulation, conductors and fastenings of - battery earth and positive cables, engine ground strap, all connections at the starter solenoid, anything else you can see. I think British cars and Lucas get an unfair rap; their electrical problems are usually caused by old age and poor maintenance. If anything looks the least bit dodgy - make it right. But before you touch anything.....DISCONNECT THE BATTERY EARTH (NEGATIVE) CABLE AND SECURE IT AWAY FROM THE NEGATIVE BATTERY POST! I suggest you pay a visit to a "pick your part" yard and look under some GM hoods/bonnets to see what's available. Or visit an auto-electric rebuilders and ask to poke around in their pile of "cores" - thrashed units awaiting reconditioning. Look at mounting lugs and brackets, and the position of the electrical connections on the rear face of the Delco. Bring a notebook to note down these things and make/year/model of car and whether it had air conditioning. The 10 SI may be found on A/C cars, but they may instead have the 12 SI or 15 SI, which have higher amperage outputs , but are physically larger and heavier, and space available is tight on the B. The 10SI has a 63-amp output, more than enough for our needs, barring monster driving/fog lamps, kilowatt stereo, etc. Delco's more modern units (eg: CS 130 series) are smaller and lighter than the SI's and have outputs up to 105-amps. They also cost about 3 times as much, and (around here at least) have a $50 core charge. FRAME: This is the front half casting of the Delco with the mounting lugs. The 10 SI has a single, spool-type pivot with a 3/8-inch bore, 2-inches long. The Lucas ACR's have slim, double mounting lugs on which they pivot. All 10 SI's have pivot and adjusting lugs 180 degrees apart, but there are differences in the centre-to-centre spacing and bore diameter. Since you will have to fabricate brackets, this isn't too important. If you get an as-is unit from a yard, just inspect carefully to ensure no cracks or broken lugs. Rebuilts are so cheap, though, that it would be a lot smarter to get a recon with a warranty. "CLOCKING": (or "clock position") ..Refers to the location of the electrical plugs/connections as viewed from the rear of the unit, with the pivot lug at the 6-o'clock position. My preference would be to have a 3-o'clock or 12-o'clock position, to simplify access to the wiring connection, but almost anything will work. If buying a recon, ask for prices of various clockings, as the price seems to relate to the rarity of that version. I went for the cheapest, with "9:00" clocking, as the core charge was only $5CDN. It came complete with pulley and fan, and with this clocking, the small boss and bolt on the back is well located to add a second brace strap. BRACKETRY: The Lucas 16ACR is physically small and light, undoubtedly part of the design criteria for the application, and with the technology and cost mentality of the day, meant that it was also modest in terms of output - 34 amps peak. Bracketry is also light-duty stuff, which means it was a good design - no more metal than necessary, has lasted 27 years, and is still in fine shape. But a little flimsy looking compared to the masses of metal seen on the donor cars to hold the Delco's. With the Lucas removed you can see how it was mounted and pivoted for belt tensioning. Its lower bracket, mounted to a bolt at the lower-right-front face of the block, is slotted and provides the adjustment capability. I replaced this with a thicker (3/16-inch or about 5mm) strip of metal 1-inch X 4-inches. Holes sized at 3/8-inch fit the MG mounting bolt and the Delco pivot bolt - drill these on (*)2-7/8inch centres. On my car, the Delco was about 3/16 inch too far to the rear for proper pulley alignment, so I kinked this bracket slightly at each end to give it a double dog-leg which positions the Delco correctly. Fit up this bracket to the engine bolt and tighten enough to hold well, but allow you to pivot it with hand strength. Start a 3/8 X 3-inch bolt in the other hole and offer up the Delco's pivot lug and mate everything up...no need for a nut at this stage. Adjust the position of the bracket to give the best clearance from engine parts, engine mount, and oil cooler hoses (bearing in mind that those can be rerouted rather easily). (* = approximate!) Now the toughest part of bracket fabrication: to properly 'sandwich' and locate the other (rear) end of the Delco's pivot lug . I used a piece of 1.75 X 1.75-inch X 3/16 thick angle iron, 4-inch length, bolted to the right engine mount, using the existing studs there. The angle iron is drilled with two 5/16 holes spaced to suit the two studs protruding upward from the mount. I didn't get the spacing exactly right and had to do a little filing to elongate one hole. The upright portion of the angle iron goes towards the front of the car, and in this you must carefully locate a 3/8 hole such that it aligns with the 3/8 hole in the first bracket mentioned above. Here's where it's complicated: the angle iron must be fixed to the engine mount in a fore-and aft-position such that its upright side is 2-1/8-inch rearward of the back face of the first bracket. This gives 1/8 clearance on the Delco's 2-inch spool pivot, thus allowing spacer washers to be inserted to fine-tune the alternator pulley alignment with the B's existing water pump and crank pulleys. You could slot the holes for the engine mount studs, but I don't like this as it could permit movement in use, which would be magnified at the pulley, likely leading to belt-throwing. With the angle iron in place another critical operation is next - drilling the 3/8 hole in the upright face of the angle iron so that it is perfectly aligned with the hole in the front bracket and the Delco's shaft and pulley are parallel to their counterparts on the engine. Slow, careful work, fit and refit, trial and error in measuring and marking, that's how I did it and all I can suggest. Once successfully done we're on the homestretch. Mount the Delco and loosely fit the pivot bolt. Check pulley alignment with the belt on. I did this visually, and so far, so good. The Delco can be shifted rearward by inserting washers on the pivot bolt. Should it need to come forward, kink the lower bracket some more, as there is not enough length of its engine bolt to allow spacers.. Make sure that sufficient washers are placed (in front, behind or both) on the pivot spool bolt to not only locate the Delco fore-and-aft correctly, but also to shim the gap between brackets, so that tightening the pivot bolt does not cause any bending stress on the brackets. Use a plain washer under the bolt head and a plain plus a lock washer under the nut. On my '71GT there is a nice handy mounting lug (part of the thermostat housing) which once served to mount the smog/air pump- long gone before I owned the car. If your B is an older model without this lug you will have to improvise, perhaps attach to the thermostat housing studs, etc. My housing is as seen in the USA Moss catalog on P14 (item #2, Part No. 460-945 "Elbow-water outlet"). On mine I attached the bracket to the lug with a 5/16 X 2.5-inch bolt. I made the bracket from 3/16 X 1-inch steel, 6.5 inches long. A test fit will show you where the slot should go - I made mine 2 inches long and 5/16 wide to fit the Delco's bolt. There is another small bolt in a boss on the rear face of the Delco, and to ward off Murphy's law, I made another smaller strap from 1/8 X 3/4 steel to fasten this to the rearmost original mounting bracket. It only needed a small slot to allow belt adjustment. The alternator is now very solidly mounted to the engine, but I noted that junkyard GM 4-cylinder cars used rubber bushed mounts for their alternators. Vibration proofing? We'll see how it does on the MGB. CLEARANCE: The Delco is shorter but fatter than the Lucas, and there is not much room to pivot it for belt tightening. I had to loosen and "re-angle" the oil feed hose coming from the cooler to the filter base, to ensure clearance. Engine movement could cause the hose to be chafed if the Delco touched it. This was really the only clearance issue, but my car has no smog pump. I don't know if the Delco would even fit with a smog pump in place. BELT: With my bracketry, a series 15, 38.0-inch belt fit well. The number on the package is "15380". There is so little room to pivot the Delco that I had to partially dismount the unit from brackets to slip the belt over the pulley. Remounted, the belt then required only slight movement of the alternator to tighten. Once on and loosely adjusted, check very carefully for belt alignment with the water pump and crank, and adjust with spacer washers or judicious (slight) bending of brackets. Belts are available in 1/2-inch length increments. My parts shop let me buy several lengths and return the ones I didn't need. A series 15 (3/8-in. width) is needed for the B and the Delco pulleys. WIRING: Electrical hookup of a Delco conversion is described very well in the Triumph online maintenance Handbook. The heavy guage Brown wire which took the Lucas' output to the starter solenoid is probably not adequate for the higher output. I twinned this with a 10-guage wire and these two in parallel are more than enough. I just strung the new one along the existing wrapped harness with black plastic ties. Lucas' original large plastic connector was left on the large brown wire and I made up a ring-and-spade (male) terminal to be fastened to the stud which is the Delco's output terminal, then plugged the Lucas onto it. I had salvaged a wiring harness from a scrapped Delco and it came with the proper ring terminal and rubber insulating boot. This was solder-spliced to the new 10-ga. It also had the snap-in connector and pigtails for the Delco's 'Sense' and 'Indicator' terminals. Slip the ring over the Delco stud, tighten the nut, with the terminals oriented so they don't interfere, and that's it. The other wires carry very little current (voltage sensing and indicator light), so I soldered small male spade connectors to the Delco plug's pigtails and inserted these into the original wiring such that terminal #2 of the Delco is connected to the smaller Brown (sense) wire and #1 is connected to the light guage, Brown-Yellow wire (indicator light). Using a tiny screwdriver, I was able to remove these wires with their female spade connectors from the plastic Lucas plug and keep it for re-conversion. Tape all wiring up so it can come to no harm. It would be a cleaner installation to cut off the Lucas connectors and solder-splice and heat shrink the Delco wires in place, but then you have lost the ability to revert to original. While a little cluttered, my installation permits a return to original in about 30 minutes, except for the disconnection/removal of the new 10-guage wire. RESULTS: Fired it up and....NOTHING!! The 12.5 volts at the battery dropped to about 9-10V during cranking, then returned to 12.5 after the engine started. Revving up had no effect. No alternator output! Shut down and check wiring -OK. Put on thinking cap and go back to the Delco book. Aha! ... it shows another wire going from the "indicator" terminal to the ignition switch, in parallel to the wire through the indicator lamp: "where an SI unit is used in place of a generator on cars having an indicator lamp". This is a calibrated resistance wire and apparently gives the field coils additional startup current above what comes through the indicator lamp, to kick off the charging function. I made up a length of wire with a 100-ohm resistor soldered in and connected this from a switched (top fuse on the upper fuse box) 12V source to the indicator terminal. Tried again and still nothing. Then with the engine turning at 1000RPM and my voltmeter showing a steady 12.5 volts, I briefly jumpered a wire from a 12V point directly to the indicator terminal: Bingo! - instant drop in idle speed of about 50 RPM and the voltmeter jumped to 14V, then climbed to the regulator set point of 14.9V and stayed there. Turning on headlamps (high beam, H4's), fan, and stepping on the brakes dropped the voltage to about 12.5, but turn signals still winked at a quick rate, and bringing revs up to about 1200 saw voltage back at the 14+ level. Shut off the engine. Voltage back to 12.5-13V. Restart. Red warning light goes out and voltage back up to 14+. This worked several times. My guess is that the alternator, in the rebuild process, had lost the residual magnetism it normally has and which combines with trickle current through the warning lamp circuit at startup to get it charging. Once I jolted it with a full 12V, that was re-established, and it now will self-energize its field coils with the warning lamp current alone. Will it still do this after an extended shutdown? Don't know yet. The best part is relatively constant voltage even at low revs and high electrical loads. Turn signals flash at a constant rate, and headlamps are bright at idle. The battery should last longer, too, as it is cycled less often and less deeply. No problems to date with engine idle fluctuation even with the higher parasitic load of the Delco. My idle speed is 900 RPM, and with the MG's crank pulley of 5-inch diameter and the 2-5/8 on the Delco, it is turning 1700RPM, capable of 25 amps, about what the Lucas would yield at cruising speeds. The Delco has a limit of some 15,000RPM, which it will never see on the B. So I now have a somewhat more modern, higher output alternator, completely remanufactured with a warranty, and replacement available at the smallest auto parts shop in the remotest village on the planet. And I have the Lucas in the spare tire well, complete with brackets and enough tools to convert back in the space of a tea-break. COST: My total cost was $110 CDN, ($79US) about $15 of which was because I had the welding shop grind brackets smooth, and round off sharp corners for appearance sake, and bought all new stainless steel fasteners. It would be hard to spend MORE on this conversion! You could pick up an alternator for about $15 at a wrecker's yard, and make your own brackets if you have the tools and skill. With a little luck, you are on the road for $25. I think you would be very pleased with this conversion, and if more output is needed, some Delco CS130 alternators have an identical mounting setup. These usually don't come with pulley or fan, but those can be sourced from a junked "SI", as the shaft diameters are the same for both at 17 mm. If you have problems or questions with your project I'll try to help. E-mail me at: wilsnfam@cadvision.com Good Luck! (Bob Wilson) |
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