The Stovebolt Site Forums The Shop Area Engine Shop Fan to Radiator Clearance

What is the ideal fan blade to rad clearance for best air flow. Setting up a SB in my 58 Apache.

1/2" max, but if you put the engine that far forward, you'll have headaches with the trans - also with engine in factory-like position it's too far back for a spacer to work ... a fan shroud is the answer, there's after market plastic ones available that fit

Bill

The eng and trans is mounted to the frame with 1/2" clearance between the distributor and firewall. I have 2" between the rad fan blade (Bottom of Blade angled forward)and rad core. I don't think I would need a schroud. Does this sound OK??

the fan should be pretty flat to the rad with the right engine mount angle, and with 2" space you'll be overheating when standing still

Bill

The fan is flat to the rad. So you are saying that I need to move the eng closer to the rad, correct? How close to the rad?

The pic of the rad shroud looks like it is at least 6" deep. I would not be able to get a 2" deep shroud in without it hitting the pullies and or alternator fan.

OK, I uncovered the truck and took some pics for you, the truck is a 56 panel with a 350/350, virtually identical to your 58 [and mine] except for a slightly different shape core support

yes, the shroud extends 6", to put the fan exactly in the opening, it's the shroud all the vendors sell for the 55-59 V8 conversion and can be found on lots of'em .... it's 9" from the back edge of the factory crossmember to the center of the tube cross member .... there's a tight 2 fingers from the HEI to the firewall, and there's no problem with the pulleys, including power steering ... and there is a 1" spacer between the water pump and fan

I'd expect that if your fan isn't pretty much parallel to the face of the rad core, your front mounts are too high, putting the engine slightly more forward to give enough dist clearance - at any rate, the fan must be within 1/2" of the rad, however you accomplish that or you will have overheating problems

Bill

I put a 283 in my 1957 Chevy truck. I used the stock 6 cylinder radiator mounting with a fan shroud. After various overheating adventures (probably nothing to do with the fan shroud and fan spacing)I ended up making a bolt-on frame from 1 inch square tubing to position the radiator close to the fan ( a little less than 1/2 inch). After finding a lot of ambiguous data about the re-location of the radiator for a v8 with stock components, I came to the conclusion the factory appeared to use different radiator mounting structure, not just moving the existing mount structure back. I could be wrong about that, but in any case, making my own mounts works for me. The plastic after-market shroud fit poorly for me and just didn't look good because of that. The fan shroud approach should work though (as per red58), my little journey with the overheating problem got me to making my own mounting frame. FYI: the over heating problem turned out to be 2 bad thermostats in a row.

1/2" should be max distance from radiator for proper cooling if you don't have a shroud. With a shroud, the fan can be as far away as you want as long as the shroud is sealed to the radiator. The fan blades should be 1/2 in, 1/2 out of the shroud opening. You want the fan to pull air through the core of the radiator, not around it, 1/2" space between the two gives you some safety room yet still lets the fan do its job if you decide not to use a shroud.

All radiators will benefit from a shroud.

Joe

Donsz - your conclusion was incorrect, there's nothing ambiguous about the assembly manual, it shows exactly how the factory did it for the 55-57's, the identical core support was moved back to other mount points on the inner fenders [there's triangular reinforcers there], and sheet metal shrouding was added in front of the rad top and bottom, as seen on this original 57 ... I have a '57 panel 'in progress' that's a factory V8, one day I'll have some good pics of it being reassembled

Bill

"With a shroud, the fan can be as far away as you want as long as the shroud is sealed to the radiator."

X2
The radiator should also be sealed to the bulkhead, and the entire bulkhead closed off from the grill except for the radiator face - all air reaching the grill must pass through the radiator. Old inner tube makes a good gasket for this.
One of the worst is sealing the nose of the hood to the top of the bulkhead, since otherwise air will just pass over the radiator into the engine bay. I've used air conditioning foam strips, but they have to be replaced every 2 years or so.

First I want to thank everyone for their help. Today I moved the engine forward 2 1/2", I now have 1/2" between the rad and fan. With the eng moved forward the stock drive shaft is the correct length, just need to get a 27 spline yoke to go into the 700R4 trans.Just a side note, I have a 55 2door that I put a SB in 25 yrs ago and there is over 2" clearance and no shroud, never had a heat problem.
Do the tube mounts need to be welded where the tube goes into the side bracket's so there is no chance of the tube turning in the brackets??