In the last few years, I have moved to a larger alternator for my 1977 MGB, that I use to run the increasing load that I am asking on my system. I have been using a Delco Remy 12si 109 amp alternator, that I love. The problem is that when the alternator is under load, the v-belt squeals. If I tighten the belt up, It kills the bearing. The solution is to transition to a serpentine belt to get better traction.

HOWEVER, The hardest part seems to be the Crank pulley available in a serpentine. Moss offers one with their supercharger kit, but if you don’t want one of those, they don’t sell one separately. There was a guy n Australia who wanted a ridiculous amount of money (around $1200 U.S.) I believe, and many people on this forum who years passed had solved the issue but were could not be contacted.

After many months of internet searches and inquiries, I started to search the junkyards. I was able to find many pulley to fit the water pump using a 6-row serpentine, with minor drilling, The one I settled on came out of a pile of pulleys so I did’t know from which car it was from but it seemed to be a common style used on many water pumps. The alternator came with a 6-row pulley so that was solved. The problem was the crankshaft pulley.

I looked at taking the old pulley and welding on the serpentine portion from another old pulley as well as a CNC solution. Nothing really seamed viable. Moss sells a small Serpentine pulley meant for low compression engines that comes in at only a few inch diameter for $169 (2109 price). That is way too small and expensive.

Long story short, I finally found an off-the-shelf solution that works.

The crank pulley has a 1.1 inch inner diameter and a 6” outer diameter. I found a crank pulley at my local auto parts store that meets the criteria, with minor adjustments. The pulley is Dorman 594-018 used on Jeeps. Around $41.95 U.S. (2019 price) https://www.dormanproducts.com/p-5219-594-018.aspx

The inner diameter is perfect as well as key, The Outer diameter is a little over 6” which works fine. The only adjustment was have the outer edge of the of the inner spline trimmed down to allow for clearance through the timing cover. I had a machine shop trim it down to 1.558” using a lathe. Since the nature of this adjustment was all around, no rebalancing of the crank was required.

I also had the hole for the water pump pulley drilled out to match the old one. All of the machine shop work for both pulleys came in amour $40 U.S.. The fit was very close with minor shimming. Due to the machining off of the crank pulley, there is a potential for cracking, But I doubt it.

Note that the existing bolt for the crank pulley which is a 5/8-16 was not long enough and needs to be at least another 1/2” longer. (Surprise) this is a non standard size which is not available anywhere. The answer, (with the aid of a UHaul tow dolly) is that I took the car to a machine shop that drilled the crank pull and heli-coil the bolt hole to a very common 5/8-18. Cost was around $20.

Depending on your setup, the belt needed will vary. I used a string to measure the size needed and then took that to my car part store to get the right sized belt.

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