I tried to install a new Hayden 2747 thermo hd fan clutch on my 1975 buick 350 and it wouldnt fit even with the supplied reducer because the water pump pilot is to long and the hole on the new thermo is not deep enough. I went to a few local parts store and all had bushings and none was deep enough , which didn't make sense because when i put a severe thermo fan clutch on my 68 buick riviera that had a 455 from a 72 centurion it bolted right on with no issues..and it was a severe clutch that were made for gmc motor homes. So anybody point me in right direction for a fan clutch that fits with out the reducer and it can be heavy duty or severe. Picture is the new hayden with the fan and old one with out fan and you can see the hole on the hayden bigger and not as deep Thanks
I think I had a similar problem when I was putting my car together. What is the length of the water pump shaft? The Hayden 2705 has a pilot depth of 1.03". https://www.haydenauto.com/en/ecatalog?partdetail=2705 The Hayden 2747 shows only .63". https://www.haydenauto.com/en/ecatalog?partdetail=2747
I don't think we are talking about the same measurement. I was referring to the same measurement G that Mart referred to above in his image. I don't think there is any way that the water pump shaft is nearly 4 inches long from the mounting flange.
That is a common problem. The NAPA/Murray 271301 or Imperial 215045 has a relatively shallow pilot hole. The problem occurs because Buick water pumps have different dimensions. The short 455 pump and long 455 pump have a different amount of shaft extension above the mounting flange. Have a look, The short 455 pump has a 1/2" shaft extension, vs. the long pump's 1". Same situation with the 350. Obviously, the 350 short pump would be OK, but the medium and long pump would have the same problem. So the solution is cut the shaft, or drill the pilot hole deeper.
Just get the right fan clutch. I recently put a Hayden 2705 on mine. It has the deep pilot hole, correct 1-1/2" fan to clutch mounting length, so the fan sits inside the shroud the proper amount. I run the 71 medium high measurement water pump.
