I recently pulled the 4 blade fan assembly off my '67 326 engine and replaced it with a fan clutch and 5 blade fan (factory style.) My question is this-my neighbor (who's a Camaro guy, but I don't hold that against him) says that the fan should ideally be half shrouded and half exposed for optimum cooling effect-is this correct? I never took notice to how the other fan looked. At present, I would probably have to install a 1 to 1.5 inch spacer to achieve this positioning. Any suggestions? Thanks!

Yes.

I thought the back side of the fan was supposed to be just inside the edge of the shroud? If not, then mine is wrong. I thought the blades would have to be "inside" the shroud to offer the best possible air movement etc.

I also would have thought that the blades centerline would be more inside the shroud, not at the halfway mark. It is a PULL system, and one would think that the more the blade center was inside the shroud lip, the more PULL it would create. Perhaps common sense does not prevail in this particular example.

However, speaking in scientific terms, the blades are indeed modeled to have a vortex point, a point at which as they spin their front area of each blade PULLS and their rear area of each same blade creates a PUSH to the rear.

My seven blade is not even half in the shroud.

And I checked some pictures that I took of a Concours perfect '68 RA and it looks about the same. 50% or less of the fan into the shroud.

The edges of the blades will move air outwards as well if they are halfway exposed. That will give you the highest amount of airflow being pulled through the rad.

Half of the blades..

half in , half out....I`ve seen som all in and still work fine...but 1/2 in ,1/2 out is recommended

I shoot for 1/2 to 2/3rd's in with clutch fans.

1/2 to 2/3rd's out for flex fans cause even at idle they pull in about a 1/2 to 1".

Aye, the "halfs" have it.

og course, the HALFS....

I guess those two halfs above Bjorn make a whole?

Mine is/was stock half in as well. ...perhaps a bit more out than in...

I took Half HALF out.... now is that a quarter? ;)

og course!