Fan blade which one to use

[Ohc Joe]

Okay I am working on a 36 sedan with a 37 flathead V8 which fan blade do I use if I remember correctly the one on the left was in the car I need to go back and look at photos is one better than the other I am doing a 12 volt conversion with the GM alternator I am waiting for the bracket and pulley to show up

[deuce lover]

The one on the right but appears to have been cut down. Its has to have the 1" hub.

[Charlie Stephens]

Remember the front bearing on the alternator wasn't designed to support a fan.

Charlie Stephens

[Ol' Ron]

I've always used an electric fan. that way I can use one belt, The Auto indystry hasn't used an engine fan for over 20 years. many reasons, I like the one where it cold the eng when it not running.
Gramps

[Ohc Joe]

This one has this attached

[tubman]

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One problem with an electric fan is that a stock 6 volt system really doesn't have enough oomph to run an adequately sized electric fan. This is particularly true of pre-war cars. A modernized 12 volt system, yeah.

[mfirth]

My 52 Vicky 6 volt system had an electric fan & 160 stats when purchased, it ran too hot for me. I went back to the original fan, 180 stats and it ran at normal temps. Just say'n...

[Ohc Joe]

I agree mechanical fans throw lots of air especially on 60s gm with fan clutch set up
My 68 grand prix and 70 buick gs never run hot

[Kurt in NJ]

Most alternators have to be spun faster than the generator in order to make rated output.
Smaller than the stock generator pulley— this will make the stock fan spin faster than designed.
The GM alternator uses the same bearing in the front as model A.
The V8 generator has a much larger bearing designed for the fan load.
A local rebuilder told me that that delco alternator was the best ever made— easy and cheap to rebuild and lasts just long enough that the people wouldn’t be pissed off at the repeat failure and he would get the business of rebuilding again.
My experience is similar,after 50 years I had to replace a bearing on the model A,in 40 years I have rebuilt the GM alternator 3 times in my chevy truck.
The 6 blade truck fans move a lot of air.
The thick belts were not made to transmit a lot of power without a good amount of being wrapped around the pulley,the tension needed to keep the belt from slipping will put more strain on water pump bushings— you might have to change to pumps with ball bearings.
What problems are you trying to cure with modifications?

[Drbrown]

(1) Not familiar with hub fit but think the four-bladed fan would be stock and the six-bladed may have been used for trucks .... ?. (2) I have 12volt neg ground system. Came with a (post-production) six-fiberglass bladed fan which works very well but makes excessive noise at high RPMs in the lower gears. Also came with 50+- amp GM alternator. I wanted to try a quiet electric fan and replaced the alternator with a 90 amp one. Most electric fans can be installed as a pushed or puller. I installed an electric as a puller (engine side of radiator) and it did not cool enough to prevent over heating in traffic. So took it all out. (3) If using an electric I recommend using a relay in the feed due to high amp draw and connect it into the ignition side of the car's system so it can't run when the engine is turned off. (4) I notice that the cooling efficiency of fan depends partly on the clearance distance between the fan blades and the face of the radiator fins. If on the engine side, too large a clearance and much of the fan's effort is wasted on thrashing the air around inside the engine compartment and not cooling the radiator. My fan has a 2-1/2 inch clearance. If reduced to say 1-1/2 inches clearance its efficiency could be improved. That of course would require fabricating a shim plate to get the fan a little closer to the radiator.

[Ohc Joe]

Originally Posted by Kurt in NJ

Most alternators have to be spun faster than the generator in order to make rated output.
Smaller than the stock generator pulley— this will make the stock fan spin faster than designed.
The GM alternator uses the same bearing in the front as model A.
The V8 generator has a much larger bearing designed for the fan load.
A local rebuilder told me that that delco alternator was the best ever made— easy and cheap to rebuild and lasts just long enough that the people wouldn’t be pissed off at the repeat failure and he would get the business of rebuilding again.
My experience is similar,after 50 years I had to replace a bearing on the model A,in 40 years I have rebuilt the GM alternator 3 times in my chevy truck.
The 6 blade truck fans move a lot of air.
The thick belts were not made to transmit a lot of power without a good amount of being wrapped around the pulley,the tension needed to keep the belt from slipping will put more strain on water pump bushings— you might have to change to pumps with ball bearings.
What problems are you trying to cure with modifications?

Thanks no problem to solve really
Doing a small easy complete rewire and things on this car been sitting since 86 so I figured a simple way was hot rod wiring kit with the one wire alternator set up from gm
I've done a few cars this way easy fast simple and cheap

[Lawson Cox]

My fan has a 2-1/2 inch clearance. If reduced to say 1-1/2 inches clearance its efficiency could be improved. That of course would require fabricating a shim plate to get the fan a little closer to the radiator.[/QUOTE]


I like about 1/2" to 3/4" clearance between fan and radiator, but again, that's just my humble opinion.

[Drbrown]

Lawson: My personal guess is that around a one inch clearance would be ideal or not more than 1-1/2 inch. Wonder if doing that would increase fan noise but probably not.

[mark180]

It took me a few tries to get the right adapter Lully for my fan. One problem I have is that the internal fan in the alternator blows back to front. ThT interacts tithe air being blown from front to back by the engine fan. It makes a whistling/howling sound.

[Ol' Ron]

I don't see the problem converting an old Ford to 12v, just change the bulbs and install a resister for the gauges and a 12v sel for the starter. If you can't do this, get another hobby.
Gramps