Fun with Fan Clutches

[Omni]

Good Morning All
As I sort through finding a workable fan and clutch combo for the '65 Newport (383 w/add on A/C, 22" 3 row radiator, factory shroud). The car did not have the stock fan on it so I do not have a know starting point. I have been informed by members here as well as well as radiator shops (Glen-Ray) that the fan should not be completely shrouded; rather it should protrude between 1/3 to 1/2 from the shroud.
In trying to obtain this 'sweet spot' I have hit a snag. I can get the fan to protrude, however, the clearance between the fan and the A/C clutch is something like 1/8 inch. I believe that the Sanden compressor sits lower and closer to the block than the RV2 compressor which it would have had if factory A/C.
I can run the fan away from the A/C clutch but then it is completely inside the shroud. The most workable fan that I have tried so far is #2863215 7 blade 18" (which shows it is for a 318 w A/C or a stock 340) with a #2707 Hayden clutch. This puts the fan in side of the shroud closer to the radiator, but away from the A/C clutch. The other option, a #2747 clutch puts the fan closer to the A/C clutch, but away from the radiator. I have a couple more fan options coming: #2863216 18.5" 7 blade 383/440 w A/C and #4140063 18" 5 blade apparently a heavy duty fan that was a Mopar Performance option 'back in the day'.
Anyway, the basic question(s): What is better, running the fan closer to the radiator, or away. How close to the radiator should the fan clutch be? Mine is about 1/2" with the 2707. Does it defeat the purpose of the shroud to completely shroud the fan?
Maybe I need to locate the stock bracketry and modify it for the Sanden? Or maybe I'm going to deep in overthinking this dilemma?
Sorry for the long back story, just trying to cover all the bases.
Thanks to all who respond.
Omni

 

[3175375]

The quick answer to your situation is: I don’t know.

However, I believe that there’s a benefit to having the fan blades protruding from the shroud, depth wise.
I believe a computational fluid dynamics (cfd) model would be necessary to optimize the location.

Here’s a couple of references about this:

Blog - The Perfect Fan Shroud Position

Fan depth in shroud - Don Terrill’s Speed-Talk

I’d recommend placing the fan blades so they straddle the edge of the shroud, clearing the other equipment (a/c compressor, radiator, etc) as best as possible.

 

[Omni]

3175375
Thanks for the links. I appears that some protrusion is best. Once the other two fan assemblies show up, I will have to decide what will work the best as to what is the optimum scenario.

Thanks again
Omni

 

[413]

Sounds like you should try it and see the results from a real world driving test. Start with it close to the radiator.

 

[CBODY67]

On my '66 and '67 Newport 26" radiator factory a/c cars, the fan sticks out of the shroud about an inch. Still plenty of room to clear the a/c clutch. In every reference I've seen, it is recommended that the fan stick out of the shroud a bit. If it is too far inside of the shroud, its efficiency is decreased a good bit, almost to the point of the shroud not helping move the air.

The only "spacer" for the fan clutch is the shaft length and related dimension from the shaft mounting flange on the water pump to the flat area on the back of the clutch where the fan physically bolts on.

You can use the catalogs at www.rockauto.com to find the correct clutch with the correct shaft length for your application. It is very possible that it will fit some Chevrolet V-8 applications from the 1980s, too.

The factory a/c fan has lots of bends and contours in the blade shapes, with a scallop out of the rear side of the outside ends. All in the name of keeping them quieter. As long as the blade diameter is close, then you get the number of blades in the mix. You can use the factory part numbers to guide you in your quest, but having that particular fan blade is not a deal breaker by any means.

DO get a thermal control fan clutch with the thermostatic spring on the front of it. The clutch with the flat face on it decouples based on engine speed whereas the thermostatic control clutch will kick in upon initial start-up, but modulate itself based on the air temp crossing the thermostatic spring. Hotter, more lockup. Cooler, freewheel.

Happy Holidays!
CBODY67

 

[Omni]

CBODY67

Thank you for your input.
I have complied a list of every fan part number (I think) that Chrysler used on big block applications from 1965 to 1971 (thanks to My Mopar). The only outlier is the 4140063 5 blade. My E Bag search has netted one - 2863216.
There are others that claim to be big block fans however, no part numbers available. Add to that the word HEMI is used in the description which then automatically drives up what they THINK it's worth.
Anyway, I have purchased both the 063 and 216 variants. The 063 arrived yesterday and when I bolted it up to the 2707 (taller) clutch the fan clutch sits approx. 1/2" from the radiator, 1/2" away from the fan clutch, and the blades protrude about 1" from the back of the shroud. Success is within sight.
Once the 216 arrives, I'll bolt that up and see which one will best 'fill the bill'.
The driving season next year will be the acid test.

Merry Christmas
Omni

 

[3175375]

Not to throw a wrench in your machinery, but @Big_John has been using a Hayden 2747 fan clutch. You can review the discussion here:

'68 Fury 318 stock radiator replacement with Cold Case