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huntznsam · 05-04-2019, 05:52 PM

In the hopes of just a tad more MPG, I installed a fan clutch to replace the fixed 7 blade fan on our 72 GMC C15 350. Yowza! MPG takes a back seat to quiet. At idle it is world of difference; on the highway I’m no longer hesitant because of the old jet-engine roar at 65mph. It sounded like I was turning 6000 RPM. I was blaming the 3.73 gears. Heck no – it was the fan!

Now I hear a rattle that needs attention, and the exhaust leak that was trivial is now more prominent.

I used the following:
Fan clutch=AC Delco 15-80245 (Amazon)
Fan blade=Dynacorn M1017 7 Blade (Ebay)
Water pump studs=Dorman 675-001 (Summit – correct 5/16-24 fine thread on the short end)
I had the balance of the hardware in my bins.

The fan sits just right, about one inch out of the shroud. I haven’t driven long enough to hear it kick in, but I don’t expect trouble.

Thanks to the experts here for all the good info – I got the part numbers from you. I hope this is useful to the next guy.

I’m a serious tracker of MPG, more for vehicle condition/efficiency than cost. I’ll see if it really makes a difference.

05-04-2019, 05:52 PM	#1
huntznsam Registered User Join Date: Jul 2017 Location: Will Co IL Posts: 30	Fan clutch install 72 GMC C15 350 In the hopes of just a tad more MPG, I installed a fan clutch to replace the fixed 7 blade fan on our 72 GMC C15 350. Yowza! MPG takes a back seat to quiet. At idle it is world of difference; on the highway I’m no longer hesitant because of the old jet-engine roar at 65mph. It sounded like I was turning 6000 RPM. I was blaming the 3.73 gears. Heck no – it was the fan! Now I hear a rattle that needs attention, and the exhaust leak that was trivial is now more prominent. I used the following: Fan clutch=AC Delco 15-80245 (Amazon) Fan blade=Dynacorn M1017 7 Blade (Ebay) Water pump studs=Dorman 675-001 (Summit – correct 5/16-24 fine thread on the short end) I had the balance of the hardware in my bins. The fan sits just right, about one inch out of the shroud. I haven’t driven long enough to hear it kick in, but I don’t expect trouble. Thanks to the experts here for all the good info – I got the part numbers from you. I hope this is useful to the next guy. I’m a serious tracker of MPG, more for vehicle condition/efficiency than cost. I’ll see if it really makes a difference.