Fan Shroud, Normal Operating Temps, Issues?

[kna4977]

How hot should a 1972 SBC 350 run and get to after it’s shut off?

Have a fan shroud but think the gap between the radiator and the shroud is too large not sure how I will rectify it but looking for opinions and advice.

[Steeveedee]

First, get rid of that fan clutch eliminator and put on a clutch that will place the center of the fan blade edges at the edge of the shroud. That MAY take a couple of trial fits. I wouldn't worry about how hot the coolant gets after the engine is shut off. It's guaranteed to go up because of residual heat in the engine that is now not being carried away. 230° isn't an unusual temperature after shutdown. I've seen elsewhere here that a 195° thermostat was installed at the factory.

[Stocker]

Originally Posted by Steeveedee

First, get rid of that fan clutch eliminator and put on a clutch that will place the center of the fan blade edges at the edge of the shroud. That MAY take a couple of trial fits. I wouldn't worry about how hot the coolant gets after the engine is shut off. It's guaranteed to go up because of residual heat in the engine that is now not being carried away. 230° isn't an unusual temperature after shutdown. I've seen elsewhere here that a 195° thermostat was installed at the factory.

Agreed 100%. I'll add that you need a heavy duty clutch fan in good working order, and a factory-style 7-blade 18" fan. If it's puking out coolant after a hot shutoff, does it have a coolant recover system (overflow tank)? It should, including a double-seal 15# (or 16#) radiator cap made for a closed system. That way you can fill the coolant all the way to the top of the radiator and you'll never lose a drop.

There's a chance you might have a shroud for a 4WD truck. It's deeper than one for 2WD, because a 4WD engine sits farther back in the engine bay.

[NGN]

Looks to be a 4WD shroud. Also I do believe you need a clutch fan when you have AC

[Stocker]

Originally Posted by NGN

Looks to be a 4WD shroud. Also I do believe you need a clutch fan when you have AC

Yep, factory A/C in my K20 came with a clutch fan.

[1970cstblazer]

Don't know the level of correctness you are going for, but 4WD Blazers/trucks used a steel connecting pipe for the upper radiator hoses with 4 tower clamps.

[kna4977]

Originally Posted by 1970cstblazer

Don't know the level of correctness you are going for, but 4WD Blazers/trucks used a steel connecting pipe for the upper radiator hoses with 4 tower clamps.

Could you share a pic and how difficult are those parts to find?

[kna4977]

Originally Posted by Stocker

Agreed 100%. I'll add that you need a heavy duty clutch fan in good working order, and a factory-style 7-blade 18" fan. If it's puking out coolant after a hot shutoff, does it have a coolant recover system (overflow tank)? It should, including a double-seal 15# (or 16#) radiator cap made for a closed system. That way you can fill the coolant all the way to the top of the radiator and you'll never lose a drop.

There's a chance you might have a shroud for a 4WD truck. It's deeper than one for 2WD, because a 4WD engine sits farther back in the engine bay.

No puking of coolant, no overflow tank has a 9# cap and it's 4x4. Shouldn't the fan clutch eliminator allow for more cooling since the fan is turning at the same speed all the time? What type of clutch would I be looking for if I go that route?

[jaros44sr]

Originally Posted by kna4977

Could you share a pic and how difficult are those parts to find?

image by [url=https://www.flickr.com/photos/97391199@N06

Hoses are available on the parts board
Just sold one last week

[Stocker]

Originally Posted by kna4977

Shouldn't the fan clutch eliminator allow for more cooling since the fan is turning at the same speed all the time?

Not sure how cooling would be different, but with a clutch fan you get a lot less fan roar, plus a very slight improvement in fuel mileage. When additional cooling is required, the clutch engages and that wonderful 7-blade fan goes to work. Factory A/C includes a clutch fan so I figure there must be benefits.

What type of clutch would I be looking for if I go that route?

Hayden 2747. https://www.rockauto.com/en/moreinfo.php?pk=1793510

[72SB]

there are 3 levels of fan clutch made by Hayden. Standard, HD and Severe Duty. AC equipped want a HD

Hayden 2747

https://www.amazon.com/dp/B000C3F370...fed_asin_title

7 blade fan wants to be half in/out of shroud

[kna4977]

Originally Posted by 72SB

there are 3 levels of fan clutch made by Hayden. Standard, HD and Severe Duty. AC equipped want a HD

Hayden 2747

https://www.amazon.com/dp/B000C3F370...fed_asin_title

7 blade fan wants to be half in/out of shroud

Thanks and which 7 blade fan should I look for if needed?

[kna4977]

[quote=jaros44sr;9345920]image by [url=https://www.flickr.com/photos/97391199@N06

Hoses are available on the parts board
Just sold one last week[/quote]

Got any more? Did they have some kind of rubber hose on each end as well with the 4 tower clamps? Anyone know the reasoning behind using a metal hose?

[72SB]

Originally Posted by kna4977

Thanks and which 7 blade fan should I look for if needed?

I have this one but other brands are available

https://www.npdlink.com/product/fan-...%3D7%26year%3D

get a coolant recovery tank for a 75 Nova and mount it inside the PS fender next to battery.

(pic of my 67 Camaro with the Nova tank)


Or buy the generic Dorman and mount it on core support
https://www.amazon.com/dp/B000E35UV2...fed_asin_title

[Stocker]

The repro fan linked above by 72SB looks identical to my OEM fan.

Originally Posted by kna4977

Did they have some kind of rubber hose on each end as well with the 4 tower clamps?

Yes. I have seen correct OEM hoses on the parts board, but I just bought mine from NAPA. The one nearest the radiator is 6" long, the other is 4 1/2".

Anyone know the reasoning behind using a metal hose?

Because the engine is set back farther in a 4x4, a longer molded rubber hose *might* sag and contact the alternator belt. If that's not a concern for you, no worries. Unless you are going for full originality.

[HO455]

Here's a thread on repop metal tubes. It gives you an idea what the originals looked like.

https://67-72chevytrucks.com/vboard/...d.php?t=624805

[HO455]

Here's a thread on repop metal tubes.

https://67-72chevytrucks.com/vboard/...d.php?t=624805

[kna4977]

Originally Posted by Steeveedee

First, get rid of that fan clutch eliminator and put on a clutch that will place the center of the fan blade edges at the edge of the shroud. That MAY take a couple of trial fits. I wouldn't worry about how hot the coolant gets after the engine is shut off. It's guaranteed to go up because of residual heat in the engine that is now not being carried away. 230° isn't an unusual temperature after shutdown. I've seen elsewhere here that a 195° thermostat was installed at the factory.

I see a long spacer if that's what is meant by fan clutch eliminator. What does the factory fan clutch setup look like what all parts am I missing?

[Stocker]

The fan clutch bolts directly to the water pump flange (sandwiching the pulley, of course) with no spacers. The fan bolts to the rear of the clutch.

[Steeveedee]

Fan clutch eliminators were a cheapo replacement for a not-really-that-expensive clutch. When I worked in a parts store, we sold those like hotcakes. Southern California does get hot.

[kna4977]

Originally Posted by Stocker

The fan clutch bolts directly to the water pump flange (sandwiching the pulley, of course) with no spacers. The fan bolts to the rear of the clutch.

Would that put the fan far enough into the shroud as it’s currently got quite a long spacer on it? Currently has a 4 blade fan with no clutch.

[Stocker]

Originally Posted by kna4977

Would that put the fan far enough into the shroud as it’s currently got quite a long spacer on it? Currently has a 4 blade fan with no clutch.

I would think so, based on my K20 with OEM shroud & fan, and Hayden 2747 clutch which was a perfect replacement for my failed OEM fan clutch.
Distance from the fan mounting surface to the water pump pulley is roughly 1 1/2".

Also, in your pic it looks like the fan is sitting too far into the shroud -- meaning the spacer is likely too long.

[kna4977]

Originally Posted by Stocker

I would think so, based on my K20 with OEM shroud & fan, and Hayden 2747 clutch which was a perfect replacement for my failed OEM fan clutch.
Distance from the fan mounting surface to the water pump pulley is roughly 1 1/2".

Also, in your pic it looks like the fan is sitting too far into the shroud -- meaning the spacer is likely too long.

having it too far in might recirculate hot air vs drawing or vacuuming in cool air?

Anyone able to share a pic of a factory setup?

[Stocker]

Originally Posted by kna4977

having it too far in might recirculate hot air vs drawing or vacuuming in cool air?

Yep. Also want to add, that fixed 4-blade fan will likely never pull as much air as a proper 7-blade. Its blades are possibly narrower and have less pitch than a fan that's designed for a clutch unit.