porsche alternator choices

[SPEEDY57TUB]

There are three early ring-shroud styles. The earliest was used with the first 911 engines and has a thick mounting flange. The next one is about 9-mm deeper and the last one is the deepest and as a result the flange is the thinnest. The earliest one can be machined to render the middle or latest of the early types. I can give you these dimensions if you need them. You will always be the safest with the earliest one since they can be machined to accept either of the three alternators.

There are three different alternators all made by different manufacturers (Bosch, Marchal, Valeo, to name a few). The bosch ones, according to my friend, a rebuilder, tend to be the cheapest and most easy to work on due to parts cost, availability, and commonality. The latest one outputs the highest amperage (90-amps whereas the earlier ones output 55-amps and 75-amps, respectfully. The fans come in 12 and 5 blades and are interchangeable. I can give you the diameter so you do not get the rare one that is a slightly different diameter (low chances since there are very few of this special and rare fan diameter out there). When you get the fan, try to get the larger of the pulleys and use a dry sump crank pulley. The new larger pulleys are available new and aren't that expensive.

I think I may have an extra 75-amp and/or 90-amp type ring-shroud. Maybe even powder coated silver and black. They have been NDT'd (Non destructive Testing) for cracks. The 90-amp one tends to be a little more desirable since it allows the use of the 90-amp alternator plus it is the newer one and you have the best possibilty to get it in great condition. Great if you need/like the extra juice. There is a company in Australia(I have the name written down somewhere) that cast and make their own alternators from Bosch parts and they use the correct axial-radial bearings as Porsche does. Also, like the original design, they utilize six-studs to locate and mount the units. They offer all three styles. I will check to see what I have. Keep an eye on this post. I will assist you as much as I can.

P.S. Try to configure your engine so it developes the heat to use the air! This is a plus since you can build a higher perf engine and not worry about cooling.

BTW, what is your engine's specs?