Clutch Fan and fan combo doesn't fit

[Montierth]

Hey guys, I am switching back to a mechanical fan with clutch on my 350 SBC with vintage air. I'm in AZ and am not seeming to get the cooling I wanted from the electric fans so I'm switching back. I read a lot of posts and realize a lot of you are in cooler climate states so recommendations may not work as well in our 115 degrees summers with AC going.

On the forums I have seen 2 recommendations for fans and clutches. I bought one of the recommended combos: Hayden 2705 clutch and Derale 6 blade 17118 fan. As you can see in the photos the fan does not fit on the clutch. How are people making this combo work? Has the manufacturer changed the parts?

The other option is the Hayden 2747 with a 7 blade fan (not sure which fan people are using) which is a HD setup. Not sure I want to do this setup as the fan runs more often and louder. But willing to do if it is the fix.

Any other combos the fit and work together? I am using a stock AC shroud and a long waterpump.

[Steeveedee]

The 2705 is a known working part, so I'd guess that the fan is somehow the wrong one.

[Montierth]

Yes I was going to return the fan for sure. just need to figure what fan to use with it the 2705. As reading the posts I'm seeing need to pair a 6 or 7 blade fan that has proper pitch.

[xr4tic]

I have that combo and the only issue was that it was a tight fit where it bolts to the clutch, but I think that's a good thing. Once you get the bolts started it goes down just fine.

Looks like you're just trying to get it over the water pump mount, you'll probably have to angle the fan to get it around the WP mount, try to do it where the slots are.

[Stocker]

My K20 has the Hayden 2747 with an OEM 7 blade fan and everything fits and it works well. It doesn't seem to engage too often, and it's not loud either. Frankly I would recommend the HD clutch for any A/C truck, especially in hotter climates. In fact my original clutch was a HD unit which is why I replaced it with the 2747.

[Montierth]

Originally Posted by xr4tic

I have that combo and the only issue was that it was a tight fit where it bolts to the clutch, but I think that's a good thing. Once you get the bolts started it goes down just fine.

Looks like you're just trying to get it over the water pump mount, you'll probably have to angle the fan to get it around the WP mount, try to do it where the slots are.

It is just too big to fit over the mount. I tried angling it and also in the slot areas.

[Montierth]

Originally Posted by Stocker

My K20 has the Hayden 2747 with an OEM 7 blade fan and everything fits and it works well. It doesn't seem to engage too often, and it's not loud either. Frankly I would recommend the HD clutch for any A/C truck, especially in hotter climates. In fact my original clutch was a HD unit which is why I replaced it with the 2747.

Yes I have been seeing your posts on the HD. Do you have a # or place where you got your fan? Just want to get a combo that fits well. I am in AZ so I think it is a little different from what most people are posting since it is so hot here in the summer. I just didn't want the loud fan running all the time but if it is what is needed then I'm all in.

[LNP]

I run a mechanical fan. I use the Flex-A-Lite 4818

[Stocker]

Originally Posted by Montierth

Do you have a # or place where you got your fan?

It's the original fan that came on the truck from the factory. I just swapped it over to the 2747 when my OEM clutch failed a few years ago.

I just didn't want the loud fan running all the time but if it is what is needed then I'm all in.

An OEM-style fan really isn't loud. The blades are unevenly spaced, which helps reduce the noise to acceptable levels. You get more of a roar when the blades are evenly spaced.

While I don't have a source or a p/n, a lot of places sell 7-blade 18" fans. Or you might find one in a boneyard -- check trucks, vans, or older full-size GM cars.

[SRU1436]

Here is my recommendation, which I just did on my 66 chevelle. It had a sbc 350, a 7 blade fan and the Hayden 2705 fan clutch. I installed vintage air on the car and that fan clutch, 2705, wasn’t moving enough air to cool the engine while the AC was on. 195 (AC Off) and it would get to 215 and climb until I turned the AC off if the air temp outside was around 95-100 (I live in California so it gets hot, not as hot as AZ). I switched to the 2747 HD fan clutch and it now keeps the engine within a normal range 180 (AC Off) and 195-200 (AC on).

I don’t hear a difference in the fan noise.

2705 Hayden fan clutch stats : Turns the fan 50-60% of shaft speed when engaged (Per Hayden)

2747 Hayden fan clutch stats: Turns the fan 80-90% of shaft speed when engaged (Per Hayden)

I hope this helps.

[Oldironside]

According to your pictures shown, the fan has to be mounted on the opposite side of the clutch.
I have the same combo. Your pictures show the side where the clutch is mounted to the waterpump pulley.

[xr4tic]

Originally Posted by Montierth

It is just too big to fit over the mount. I tried angling it and also in the slot areas.

I just measured mine, the WP mount is roughly 2.6" and the fan is just slightly bigger than that between the larger diameter part of the hole.

I couldn't get an exact measurement because it's installed and the shroud was in the way of my calipers, but your parts look correct, you just need to find the right angle to get the fan over the mount.

[Steeveedee]

The fan should just fit over the flange of the clutch. I measured my clutch (Hayden 2747) and the flange is 2.695. so, just over 2-11/16".

[72SB]

depending on what WP, the fan clutch "may" need the sleeve to reduce its opening size where it mates to the nipple of WP. Most fan clutches come with it. Simple to press in with a mallet if needed

This is to center the fan clutch to WP

[Montierth]

I appreciate everyone's input. So I got home last night and spent several minutes twisting and contorting the fan and some how with pressure, lining up the tabs on fan with the clutch slots I was able to get it on. Man it was a tight fit but got it on. After I put the fan in the AC shroud I see I probably could have gone with a 19 inch fan. Gonna put it on this weekend and hopefully see cooler temps than using the dual electric fans.

Since I got this setup I will install and try it. But sounds like I may need to go with 2747 and use the 6 blade fan - if I can get it off.

[Steeveedee]

I ended up with a 19" fan with the 2747. I formed my own shroud, because the fan's front edge is about one inch from the radiator. It's always been that way, but other trucks have more space. I was having problems running hot, and the fan didn't couple with the shroud. You could probably get away with filing a tiny bit off of each of the tabs on the fan blade. A little bit would be all it took, and won't affect the balance, being that close to the hub.

[SRU1436]

Make sure the fan is half way in and out of the shroud.

[tim_mc]

I double checked and am running a Derale 18" rigid 6-blade fan (17118) with a Hayden 2705 thermal clutch fan. Works great in summer heat and I don't remember any assembly issues.

[Grumpy old man]

6 Blade fan / Hayden 2705 clutch and short water pump . LMC A/C fan shroud . Champion CC369 radiator . Gates belts and hoses .

[Steeveedee]

^ That's matched up real nice! I wish my truck had been like that.