porsche alternator choices

[zen]

which of the different amperage alternators can be used in a TIV conversion for a '73 1300? i have a '72 914 engine i will be converting. really don't know what the impact is of using the different sizes.

as a follow up that, i have a guy giving me a 5-blade fan for free. if i go with that over an 11-blade fan, what alts fit in the 5-blade?

[SPEEDY57TUB]

The more juice the better. Word of caution: The early 11 or 5 blade setups have variations such as internal vs. external regulators and there are three different mounting depths and therefore three different shroud-ring depths. There are even two different fan diameters too, although one of them is very rare compared to the other. Also, there are two different pulley diameters. These variations are not including the very different 12 blade configuration. :confused:

I currently have some of the different parts for the different early setups. I recommend you get a setup that includes the matching components or do a little bit of research to get what you ant from different sources. Oh yeah, to throw in another wrench into the gears :takethat: , there are some ring-shrouds that were machined by Porsche to fit a deeper and higher amp alternator in order to phase out the inventor. Unfortunately, the part was kept until the new casted parts were procured. You can always machine down the mounting surface by about 9-mm (the difference between the two). I have my local machine shop do this once in a while for me. Good luck. Email me if you need some help.:confused:

[zen]

great info. thanks. i was afraid that may be the case. i had heard that getting the whole assembly is better. just having a hard time finding one at a fair price. plus it is hard to pass up a free fan. i don't really have the time to source around and deal with the variations though. i want to have the car together by the spring.

let me know if you have any assemblies you are interested in selling our can point me to a place with good prices.

thanks again!!!

[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?

[zen]

again, great detail on the info. i will be running a mostly stock '72 2.0l 914 (GA) engine. will be changing to carbs and larger exhast. this engine is supposedly a runner and i will run it until it dies. everything i am buying i am buying with the plan of using on a 2270 when this engine gets the rebuild. so some of this may be overkill for this engine at the moment.

i am really only looking to go with the 911 fan (FAT shroud) since the DTM seems to be difficult to get a hold of right now and the FAT can go on without machining. i may change up when i rebuild.

just got an email from a guy with an assembly with a 55-amp 11-blade. not sure of year. he is asking $300 which seems to be midline pricing. i assume that it is probably an early one based on your info. i may just grab it while i can.

not sure if i will need the extra juice of a larger alt or not. i will be running a mild sound system, 914 gauges, h-4 headlights, sidemarkers, and fairly normal taillights. nothing else unusual while running. i will have an alarm and solenoids for the doors (shaved handles).

[SPEEDY57TUB]

55-amp is the early one and it most likely needs an external regulator. If you find a later alternator in the future, you can machine the ring-shroud to accomodate it. Find out what alternator make does he have and what pulley size. If it requires a rebuild, the manufacture makes a big difference. The larger pulley is the one you want (I believe it is about 3.75" vs. the smaller 3.25" one). Use a 5" crank pulley so you do not spin the alternator/fan too fast. I would bump up the compression a bit and play around with the timing. Eventually when you build the 2270-cc, you can build it to create the heat to warrant the extra cfm that the 911 fan system produces. Looks like you are doing the same as I am in regards to engine plans. I plan to go with a RAT 2270-cc eventually.:D

If you need a ring-shroud, I have several available.;)

Keep in touch if you need help.:cool: