I some help spending some money for the engine

[OregonNed]

One of my projects this last December was cleaning up my flex fan and buying a new fan spacer. However, I want to instead go the routed of a solid fan with a fan clutch to reduce under hood noise, as well as safety. Can I get some recommendations for a fan and clutch from the collective knowledge here? My C10 has a 327 with a long water pump. I'm currently using this flex fan with 2" spacer. Distance from fan to radiator is 2" The truck isn't driven a lot, mostly cruising around town, with some occasional freeway driving, that I suspect will increase during the warmer months. Thank you. Attached are pics of what I have.

[toolboxchev]

Just looking online, FLAPS NAPA, I located a unit for a 78 3/4 ton.

Looks like if you installed it removing your spacer it would still be at the same distance.

I have my fan shroud off my stock motor setup with 350 and 4 core radiator. I will go get a measurement and post back in a few. I have been wanting to do this mod. 27 bucks for the unit. I do know there is a heavy duty application available. Years ago when I worked at the FLAPS I got a HD unit for a buddy for approx. 50 bucks my cost. It retailed for almost a 100.

[Stocker]

I am on record as NOT being a fan (heh) of flex fans, so good on ya!

Lemme do some digging. I know I'd recommend a shroud, an 18" diameter 7-blade fan, and a heavy-duty fan clutch. I'll be back later with more specifics....

[OregonNed]

Thank you guys!

[Ol Blue K20]

Originally Posted by Stocker

I am on record as NOT being a fan (heh) of flex fans.

Ha...lol....clever....

[Stocker]

I found my HD fan clutch at my local NAPA store. The NAPA p/n is 271303, fan clutch #2747, made by Four Seasons in Lewisville, Texas. It has performed flawlessly on my K20. I don't have it here to measure distance from pulley to radiator though, so that should be checked first.

Useful info from Hayden's website:

What is the difference between a standard, heavy and severe duty fan clutch?

Answer: Each fan clutch type is designed to simulate the performance of the original equipment clutch that it replaces. All fan clutches are for specific applications and should be applied only on the vehicle for which they are cataloged. Use of the incorrect fan clutch may result in poor cooling, excessive noise, reduced fuel economy or fan clutch failure.

• Standard Duty Thermal: Turns the fan 50-60% of shaft speed when engaged. Used with fans with lighter pitch (1-1/2" of pitch). Flat plate impeller design with 30 sq. in. of working surface.

• Heavy-Duty Thermal: Turns the fan 80-90% of the shaft speed when engaged for increased cooling. Used with deeper pitch fans (2 1/2" of pitch). Land and groove design with 47 sq. in. of working area allows higher operating RPM's.

• Severe Duty Thermal: Turns the fan 80-90% of the shaft speed when engaged. Used with deeper pitch fans. (2- 1/2" of pitch). Land and groove design with 65 sq. in. of working area. Larger working surface provides cooler running and longer life expectancy.

[Stocker]

A bit more.... Hayden changed their site and I found a pdf with pics that clearly shows the differences between standard duty, heavy duty, and severe duty fan clutches. Easy to spot if you know what to look for.

https://www.haydenauto.com/media/567...ts_6980012.pdf

[dmjlambert]

That Hayden document does not have one that looks like my 1969 CST/10's clutch. Is this heavy duty? I have 7 blade fan, 2.5" fan pitch, was 4 row radiator (now 2 row Engineered Cooling Products aluminum, same radiator size as 4 row) and truck has factory A/C. When I attempt to look up a replacement clutch the only fitment matches on the auto parts store websites are for standard duty clutches.

[toolboxchev]

I remember that Hayden site, very informative. I believe they are the leaders in the industry.

Following are some pics for reference. I have no cooling issues with or without the fan shroud. Have it off for evaluation of cooling performance.

Stock Gen 1 350 with a short pump I believe.

This should get you in a better ball part as I believe your fan it too close as I recall. My fan sits about 1/2 in 1/2 out with the stock fan shroud.

[toolboxchev]

Originally Posted by dmjlambert

That Hayden document does not have one that looks like my 1969 CST/10's clutch. Is this heavy duty? I have 7 blade fan, 2.5" fan pitch, was 4 row radiator (now 2 row Engineered Cooling Products aluminum, same radiator size as 4 row) and truck has factory A/C. When I attempt to look up a replacement clutch the only fitment matches on the auto parts store websites are for standard duty clutches.

Far as I know, none of our model year trucks came with a fan clutch. Someone will clarify. I believe you have to go with 73 and up Chevy trucks for parts reference at the FLAPS......they will not have any idea with their thinking?????


What make, model, year and option????

[Stocker]

Originally Posted by dmjlambert

That Hayden document does not have one that looks like my 1969 CST/10's clutch. Is this heavy duty? I have 7 blade fan, 2.5" fan pitch, was 4 row radiator (now 2 row Engineered Cooling Products aluminum, same radiator size as 4 row) and truck has factory A/C. When I attempt to look up a replacement clutch the only fitment matches on the auto parts store websites are for standard duty clutches.

That sure does look like a heavy duty unit to me (fins across the entire front except the center where the thermal spring is located). Your truck sounds as though it's equipped the same as mine, right down to the 2 1/2" pitch. I went through exactly the same process, the only ones listed were light duty. We looked up a mid-seventies K30 to find the heavy duty clutch, and it was a perfect fit.

toolboxchev, I just saw your post. My '72 came stock with a HD fan clutch. Dunno when they started but it may have had something to do with factory A/C.

[dmjlambert]

Originally Posted by toolboxchev

Far as I know, none of our model year trucks came with a fan clutch. Someone will clarify. I believe you have to go with 73 and up Chevy trucks for parts reference at the FLAPS......they will not have any idea with their thinking?????
What make, model, year and option????

I don't know. That is interesting. My 1969 CST/10 was relatively unmolested and I've only done modest upgrades such as HEI and later model Quadrajet. This was the clutch and fan it came with when I got it. It is a stock 350 engine, with factory A/C and 4 row radiator, and 7 blade fan with 2.5" pitch. So I'm thinking it would have come from the factory with a heavy duty clutch.

[dmjlambert]

Originally Posted by toolboxchev

Just looking online, FLAPS NAPA, I located a unit for a 78 3/4 ton.

You have me curious, you used the word FLAPS twice and one of the times you said "at the FLAPS." What is that? A city or place name, reference book to look stuff up in? When I look up FLAPS NAPA on Google I see ads for mud flaps that NAPA sells.

[Stocker]

Friendly Local Auto Parts Store

[dmjlambert]

Originally Posted by Stocker

Friendly Local Auto Parts Store

I love it! Thanks, I learned something good today.

[OregonNed]

Originally Posted by toolboxchev

Far as I know, none of our model year trucks came with a fan clutch. Someone will clarify. I believe you have to go with 73 and up Chevy trucks for parts reference at the FLAPS......they will not have any idea with their thinking?????


What make, model, year and option????

My '68 probably did not, then... I think I will just replace the fan for a solid non-flex type and skip the clutch. Thanks, all.

[Steeveedee]

Clutch type fans were available for trucks in '68.

https://www.napaonline.com/en/search...=semantic&se=1

[Stocker]

Originally Posted by OregonNed

My '68 probably did not, then... I think I will just replace the fan for a solid non-flex type and skip the clutch. Thanks, all.

It *might* cool well enough, though not as well as a proper clutch fan setup..... and you will probably get tired of hearing the constant roar. Not to mention a slight fuel mileage hit, not that it matters much on these old dinosaurs.

[MySons68C20]

My 68 C20 came with a clutch fan with the original 327. I cleaned it up and it keeps the new 383 cool.

[toolboxchev]

Just poking back in to see if you spent a million!

I do like the looks of that flex fan you have, aluminum blades I presume??? I appears to be a much lighter version of the old solid heavy unit which will pull a lot of air.

Pics when your done would be nice.