Ok, here is the info I have for a 1975 clutch fan assembly. Eventually Opel used a fan clutch like the Hayden 2558, that screws onto the water pump pulley. Unfortunately, my computer that has the info for that setup isn't accessible until September but I can provide everything needed for the 1975 setup, which is what I have in my garage waiting to be used in my 2.4L build.
This is what the whole assembly looks like once done...
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The water pump is a GMB 155-2010 and is a replacement part for GM part number 80 090 517, which is the part number on the NOS water pump I have. You can find the GMB water pump online through various sources. It comes with a gasket.
The original fan clutch was GM p/n 08960124 or Opel p/n 1340151. I have a Beck Arnley viscous fan clutch as well, which is p/n 130-0060 but this is also a NOS part that I don't think Beck Arnley provides anymore. This was a somewhat common fan clutch however and was used on the
Volvo P1800,
MG Midget 1500 and Triumph Spitfire, and the
Ford Capri. So, there are a lot of part numbers connected to this viscous fan clutch and that also makes sense. Car manufacturers prefer to use a part already made whenever possible. This is a somewhat unique design actually for a fan clutch, most rely on a threaded attachment or bolt to the water pump in a few spots. I have an alternate GM p/n - 90091367 - for this fan clutch and a Ford p/n too - 75EB-8A-616AA - which is for the Ford Capri. The Ford part number is straight from my Beck Arnley clutch. This will likely be the most expensive individual part of the assembly, between $100 and $200.
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The fan itself could be tricky to find if the sources I have no longer have any in stock. The GM p/n is 08960064 and the Opel p/n is 1340069. Opel GT Source used to have a 7 blade fan (p/n 11034) but they don't show it online. I can't even track down the original part numbers anymore online and I used to find two places that had the 5 blade fan listed. The only lead I have on this fan right now is on eBay in Germany...
Original Opel Manta A B Rekord E Fan Impeller 08960064 | eBay
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There might be a Volvo fan that works however. When looking up info on the fan clutch, the Volvo fan showed up as a related part on eBay and it looks pretty similar.
vintage volvo b20 fan blade p1800 1800e 1800es 140 164 oem clutch fan 679276 | eBay. The Volvo part number is 679276.
As for the hardware to finish this off, I bought what I needed from McMaster Carr. Socket head bolts / screws seem to be used a lot on CIH engines, so I kept up with that. For the four smaller bolts and nuts to attach the clutch to the fan, I used
p/n 91270A290 for the non-marring locknuts with spring-lock washers and
p/n 92235A242 for the socket head bolt. For the center bolt, it needs to be a left-hand thread M10x1.5 and somewhere around 15 to 20 mm long. I used
p/n 90605A302 and used
p/n 91116A390 as a suitable washer to go with it.
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The fan will be the limiting factor for anyone wanting to do this and it could take some hunting for people to find one. Eventually Opel went with a different and more typical setup, where the clutch screws onto the water pump pulley. That newer design does stick out a little more however and I don't know if it will still fit in a GT or would it hit the radiator? I know the ‘75 design that I’m covering here will fit, it’s the most compact option for a clutch fan. I also like oddball, year-specific things in cars so I wanted to use the setup from the 1975 Manta. Based on the info I have shared in this post, someone could get all of these parts for $282 plus shipping and taxes but that only works for the first person to buy the fan from Germany.
If someone wants to do this and asks nicely, I can provide the washer and 4 smaller bolts and nuts, since I have spares. They would only need to buy the center bolt.
