thermal fan clutch issues - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BrianG · 09-15-2015, 09:45 PM

I am reassembling my cooling system and am switching from a flex fan to a thermal clutch fan. I have a 69 4x4 with the engine in the back position as original and the correct fan shroud. I have a new flex-a-lite thermal fan clutch part number FLX-5555 and a new fan blade. My problem is, the fan does not sit correctly in the shroud. It is only in by about a half inch, maybe less. After quite a while searching, I have read that most say that a spacer is not needed with a clutch fan. Some even recommend against it if it IS needed. From those posts, it appears that there should be a longer thermal clutch fan available. I cannot find Thermal clutches on Flex-a-lite's website. Maybe they got out of the business. So... Who has replaced their cooling system to use a thermal clutch fan, and what part number/manufacture did you use? I hate to have to spend another $50, but I want it to be right also.

**Jurassic-1** · 09-15-2015, 10:08 PM

I have a AC Delco Thermo Clutch on my 72 Blazer. It is for a 454 big block engine. It sits perfectly in the shroud and it has been on the Blazer for about 15 years and still works great. I also have the same one on my 70 CST both are used with no spacers.

BrianG · 09-15-2015, 10:35 PM

Quote:

Originally Posted by Jurassic-1

I have a AC Delco Thermo Clutch on my 72 Blazer. It is for a 454 big block engine. It sits perfectly in the shroud and it has been on the Blazer for about 15 years and still works great. I also have the same one on my 70 CST both are used with no spacers.

Does the 70 have a small block or big block? I'd also be interested to know if you have a long or short water pump (I have the short). How far does the fan sit from the water pump pulley?

Andy4639 · 09-15-2015, 10:41 PM

Here are a couple of my 305 TPI motor with clutch fan sitting inside the shroud. Never had a minutes worth of trouble out of it. had to replace the blades once when a water pump took out the blades though.

BrianG · 09-15-2015, 10:48 PM

Quote:

Originally Posted by Andy4639

Here are a couple of my 305 TPI motor with clutch fan sitting inside the shroud. Never had a minutes worth of trouble out of it. had to replace the blades once when a water pump took out the blades though.

Andy, your clutch looks like it has a much longer shaft than mine does. Is that a GM clutch?

Andy4639 · 09-15-2015, 11:26 PM

I'm not 100% sure but it was on the 307 when I bought the truck in 96. I moved it to the 305 and bought a new 7 blade GM fan and it matched right up.

**Stocker** · 09-15-2015, 11:32 PM

Brian, that pic of Andy's clutch looks same as my OEM fan clutch. If yours is shorter, it could be the wrong one.

**Jurassic-1** · 09-16-2015, 09:26 PM

Both of my 350 engines are small block. Short water pump.

09-15-2015, 09:45 PM	#1
BrianG Registered User Join Date: May 2011 Location: Oakley, Michigan Posts: 735	thermal fan clutch issues I am reassembling my cooling system and am switching from a flex fan to a thermal clutch fan. I have a 69 4x4 with the engine in the back position as original and the correct fan shroud. I have a new flex-a-lite thermal fan clutch part number FLX-5555 and a new fan blade. My problem is, the fan does not sit correctly in the shroud. It is only in by about a half inch, maybe less. After quite a while searching, I have read that most say that a spacer is not needed with a clutch fan. Some even recommend against it if it IS needed. From those posts, it appears that there should be a longer thermal clutch fan available. I cannot find Thermal clutches on Flex-a-lite's website. Maybe they got out of the business. So... Who has replaced their cooling system to use a thermal clutch fan, and what part number/manufacture did you use? I hate to have to spend another $50, but I want it to be right also.

09-15-2015, 10:08 PM	#2
Jurassic-1 Registered User Join Date: Jul 2007 Location: New River Arizona Posts: 1,180	Re: thermal fan clutch issues I have a AC Delco Thermo Clutch on my 72 Blazer. It is for a 454 big block engine. It sits perfectly in the shroud and it has been on the Blazer for about 15 years and still works great. I also have the same one on my 70 CST both are used with no spacers.

09-15-2015, 10:41 PM	#4
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: thermal fan clutch issues Here are a couple of my 305 TPI motor with clutch fan sitting inside the shroud. Never had a minutes worth of trouble out of it. had to replace the blades once when a water pump took out the blades though. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

09-15-2015, 11:26 PM	#6
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: thermal fan clutch issues I'm not 100% sure but it was on the 307 when I bought the truck in 96. I moved it to the 305 and bought a new 7 blade GM fan and it matched right up. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

09-15-2015, 11:32 PM	#7
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,722	Re: thermal fan clutch issues Brian, that pic of Andy's clutch looks same as my OEM fan clutch. If yours is shorter, it could be the wrong one. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

09-16-2015, 09:26 PM	#8
Jurassic-1 Registered User Join Date: Jul 2007 Location: New River Arizona Posts: 1,180	Re: thermal fan clutch issues Both of my 350 engines are small block. Short water pump. Last edited by Jurassic-1; 09-16-2015 at 09:27 PM. Reason: Forgot info

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