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MG MGA - Fan Belt for Alternator Mod

This week I installed the Moss alternator kit in my MGA. I have an early 1800 3 bearing engine in the car. The fan belt that was shipped with the kit was the MGA / early MGB fan belt; Moss part 460-990. The alternator installation was easy, but the belt itself was a bear to install on the new alternator, even at full droop. There is more tension on the belt (and therefore pressure on the alternator and water pump shafts), even at full droop, than I am comfortable with...no movement or adjustment of the alternator is possible with the belt on. In my 40 years of messing with fan belts, I think it is way too tight. The flex of the belt is MAYBE one-eighth of an inch, if that. You guys with alternators on your MGAs...is the MGA belt the right belt for the alternator conversion or should they have shipped me a later MGB belt?
Frank Nocera

Hi Frank. Your belt does sound too tight, even for an alternator. As a suggestion, why dont you run the engine for half an hour or so, and see if the belt stretches a bit. Often, new belts stretch a considerable amount after a short period of running. If you are concerned about doing that, then I recommend that you take the belt to an automotive parts store, and buy a new one that is slightly larger in size. Cheers! Glenn
Glenn

I saw a different NAPA fan belt part number (7360) on an MGB tech site that had instructions on converting from generator to alternator. Bought that belt from NAPA this morning; it was longer than the (MGA) belt supplied in the kit by Moss, and allowed the alternator and belt to be properly adjusted. Alternator is now mounted, belted and adjusted. Yay!
Frank Nocera

I just received my Moss alternator kit but haven't checked the belt size yet. I too have a B engine. The MGB fan pulley is a different size (larger) than the MGA so it makes sense that the MGA belt they sent you is too small. If there's no adjustment possible it's not the right belt for the job.
Mark J Michalak

Mark,
If you were sent (as part of the alternator conversion kit) Moss fan belt part 460-990 (a Quinton Hazel...QH... Belt, part #QBA900) it is the wrong size. Don't even try to use it; send it back. BTW, the installation really is straight forward and easy....well, except for figuring out which of the two identical brown wires at the A terminal post on the regulator (that disappear into the wiring loom) is the one going to the fuse, and thus the one to be tapped. See my other thread on that issue.
Frank
Frank Nocera

Frank,
There can be variances in the belt needed regardless of the conversion you do and the car (even same model, same year, same alternator), that is why I never recommended a particular belt for my Bosch Conversion. There is always the possibility of production and other variances of the components involved which, for whatever reasons do exist, but are unaccounted and make any recommendation basically a generality or suggestion of what should be used.

My suggestion is to take the belt that Moss sent you to the local NAPA or other parts house, and ask for one about 1/2" ~ 1" longer and a similar width. You would be surprised how much difference in fit there will be between the two. With a next size larger unit, you should be good to go.

Or, you can call Moss and ask them to exchange the belt for you. They know what they did to determine the size of the belt they sent you, and perhaps they can shed some light on the differences between your installation, and their baseline parameters. They may even have a range of belts available for situations such as yours ~ however, only if you ask. Good luck.
Bob Muenchausen

Thanks Frank. I have an alternator on the car now but the geometry isn't quite right and I keep breaking mounting bolts. I can't wait for a nice clean hassle-free fix.
Mark

Ouch, Mark, that is not a good sign. I have heard of Delco's breaking off water pump mounting brackets, but not mounting bolts. Perhaps the ones Moss sent you were not high enough heat treat/high enough strength? Sounds overstressed.
Bob Muenchausen

Mark,
I replaced the Moss-supplied bolts from the alternator conversion kit with hardened bolts from Lowes before I did the installation. Sounds like you have the same problem I had; fan belt is too short and too tight. Try a NAPA belt, part #7360.
Frank Nocera

No, it wasn't a Moss kit that was breaking. I did a Delco conversion like the one shown in the Rowdies Tech Tips manual. This uses a 7-inch bolt with a long spacer. It worked fine with no problems for a couple years but then I started to take the car on endurance rallies. During all the bouncing and jostling of logging roads and snowmobile trails the long bolt would sometimes snap. I tried a hardened bolt and then the water pump ear snapped. I cried "no more" and forsook the Delco forever.
Mark

I just installed a Lucas alt. on my car and used the rear mounting bracket from Moss instead of the long mounting bolts and spacers.
Kris
Kris Sorensen

Frank: If the belt is too tight, please e-mail me directly asap. If Moss is including the incorrect belt we need to know, so we can fix the problem.

I'm blocking kit sales till this is ironed out.

I'm also confused about replacing the supplied bolts. All hardware in the kit is Grade 5, which is the correct grade for application.


regards

Kelvin.
KJ Dodd


For the archives:
I emailed Mr. Dodd and suggested that there is no need to stop sale of the alternator conversion kits; the kit is for MGA 1500 and 1600 engines and my MGA has an early MGB 18G engine. Even though the 18G takes an MGA fan belt, the fact it was an 18G and not a 1500 or 1600 could have been the issue. I suggested there may be a need for two kits; the second for early (generator) Bs that may take a slightly longer fan belt.
Frank Nocera

Is this possibly just a case of a bad substitution of a 900mm Metric belt for a 36" Imperial belt. It would be about 5/8" too short. The part numbers seem to suggest that might be the case, QBA900 and Napa7360. Belt manufacturers usually incorporate the belt length in the part number.
John DeWolf

Mark,
Sorry, I misunderstood which conversion you were talking about.

I had an email conversation with Barney Gaylord about this same extended tube type of rear mounting I was describing for the Bosch MGA conversion I used to offer. I had picked this method up from someone else. Barney's comments convinced me that even tho I was having the same luck as you did (your first two years), it was not a well engineered mounting. I had previously noted on my former Bosch MGA conversion site that the rear mounting bracket Moss now offers was a more secure mounting. I still think that the Bosch Alternator is a good alternative, and I may resurrect my site specifying use of the Moss rear bracket, but maybe not.

The Delco conversions I have heard about which caused problems such as you describe, Mark, came from MGB folks over on the MGB Experience BBS this fall ~ an interesting admission about a problem with a very popular conversion and piece of "Detroit Iron."

Bob Muenchausen

Bob,

Live and learn, right? The problems with that conversion, specifically, are: 1. Unless you have the proper machining tools it's hard to cut the alternator ear *perfectly* flush to the water pump ear 2. The alternator mounting hole that lines up with the water pump ear and the rear mounting bracket is very close to, but slightly larger than, the diameter of the bolt you need to use. It's almost unnoticeable at first, but it really requires sleeving the alternator mounting hole to get it right. 3. When using the long spacer technique you are not applying any sort of direct pressure on the alternator itself. You are essentially creating pressure between the water pump ear and the rear bracket, sandwiching the alternator and spacer together over a 7-inch span. Not good.

I could have done an MGB/Lucas conversion from the start, but I figured AC Delcos (or Boschs) were cheaper and more readily accessible if I broke down in a random small town. But apparently you can get Lucas alts at AutoZone. My advice for anyone doing an alt conversion is to go with the MGB/Lucas and use the Moss kit if you have to.
Mark

The Lucas 18ACR should have all the juice anyone would need, and is easily wired up in the same manner as the Bosch. When I originally wrote up the Bosch conversion for the MGB, I didn't know that, but some kind Triumph folks pointed that out, and in the website's second year, I changed the wording to reflect that the choice between a Bosch and a Lucas was a coin toss.
Bob Muenchausen

This thread was discussed between 29/01/2005 and 03/02/2005

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This thread is from the archive. The Live MG MGA BBS is active now.