I have a '72 coupe with AC, 350cu engine, with a clutch fan (six 4" blades). Standing to the side of the radiator shroud I can see 1" of the fan blades protruding from the rear of the shroud - so, more than half of the blades are inside the shroud. However, the front leading edge of the blades are still 3" from the top of the radiator. I don't have cooling /overheating issues but I was wondering, shouldn't the fan blades be closer to the radiator. My AIM gives details for a 454cu engine (minimum 1/2" gap at the top, but provides no standard gap figures.) Does anyone have the suggested gap measurements for fan/radiator installation?
I am helping a friend restore a '57 Chevy and its requirement is 1/2" gap (that radiator is perpendicular to the fan so there is an even gap from top to bottom>), thus my question.
I know, "if it ain't broke, don't fix it", but maybe it would be a little more efficient if I inserted a fan spacer.

 

I believe fan blades at the edge of the shroud is correct.

 

JimT,
You are right..."if it ain't broke...don't fix it"

I have had many original Corvettes come into my shop and some have the fans spaced like what you have, and some are actually have the fan blade width be in sticking otu past the shroud half the width. With one inch sticking out past your shroud should not be a concern to you. The fan is pulling air well like that at idle....right?

I am not an offical brainiac on 55-57 Chevy's. But I do now that when a radiator has NO shroud or partial shroud, the placement of the fan as CLOSE to the radiator is IMPORTANT to allow it to create a draw of air that is useful for cooling at idle.

Your Corvette does not fit into that design element. 1957 to 1972, In 15 years improvements were made, flow design of radiators and many others that are not relevent to this issue. Apples to oranges, both are fruit from a tree but are very different.

The issue that usually concerns me is when people replace radiators and neglect to invest in the foam seals that go around the radiator to the radiator support. Or the seal(s) that are on the top of the radiator support that seal to the underside of the hood. Leaving these seals out is a BIG mistake. Making sure that the seals on the shroud (if originally equipped) are intack and sealing correctly. The idea is to make the fan pull air THROUGH the radiator and not allow the air to cavitate or be pulled from another area other than the core surface area of the radiator.

Also the lack of making sure that the lower air dam is installed for better air flow. And sometimes ( in rare cases of really, really high perfornace engined cars) not having a front license plate on the car to allow more air flow when dealing with the 1963-1972 Corvettes.
"DUB"

 

Thanks for the info! I've got the radiator pretty well sealed as I've replaced all of the radiator shields (top, bottom, and sides), have the air dam in place, and, do not need the front license plate, so I am getting plenty of air flow.
The '57 we are working on has no shroud so a close fit is necessary, and as you might guess, the radiator sits squarely to the fan and not angled as with our cars. I was just wondering at what point in fan placement does the fan begin pulling air from around the shroud instead of through the radiator.
I have entirely too much idle time on my hands! I am so used to working on the car, that when there is nothing to do, I can't stand it.