346 Five Bladed Fan

[Virgil Perkins #19943]

Regarding a 346 in a 1941 Cadillac, has anyone run a 4 blade and 5 blade fan both in the same exact setup and noticed any difference in the running temperature of the engine either while driving or idling?
Thanks, VP

[Bill Ingler #7799]

Hi Virgil: I now have the 5 blade fan on my 47 and I did run the 4 blade on the same car . I see no difference as least in my case. Running either 4 or 5 blade here in Arizona on a hot day will show my temp gage running just short of the H mark in traffic on a 90+ day  and slightly above the middle at around 55-60 mph.  I have an extra 5 blade which I was going to put on the 41 but I see no reason for changing as the 41 runs cool at idle or cruise. I notice there is a 5 blade fan now on ebay which has not drawn a bid.

[Doug Houston]

Actually, the 5 blade fan is important, only at low engine speeds, such as at idle. or possibly lugging in high gear. At highway speeds, it's actually in the way of the air flow, as the ram air does all the work. On current model cars, the electric fans are never running unless the temperature gets up, for some reason.

[The Tassie Devil(le)]

Plus, an engine driven fan isn't needed above speeds of 35 mph, and is actually a hinderance as the air passing the vehicle is sufficient to cool the engine, until one is travelling faster than 100mph.   Then the engine driven fan is required to pull the air in.

Plus, a 5 blade fan also assists in stopping harmonics me thinks.

Bruce.

[Virgil Perkins #19943]

    Thank you all for the response.
I was wondering whether or not it would be worth the effort to change over to a fiver. My 41 normally runs smack dab in the middle most of the time. If I stay at or over (according to the speedo) 85, it will go over 3/4 or more on the gauge. When backing down to reasonalbe speed of 65 to 70, it will return to midpoint.
    Beside that, I don't wanna break the law .         Some hot days, like we are now experiencing in Indiana (in the mid 90's for 12 days straight) it will heat up while at stoplights and then cool back to midpoint in a block or two. I think it wise to leave it as is.
And,yeh Bill, I know that mid 90's is nothing in AZ. but it is hot for this neck of the woods.
THANKS AGAIN, VP

[Bill Ingler #7799]

There is an old saying  Don`t try fix something that is not broken. I think we have all tried this once or twice with old cars. Comes back to bite you.

[Doug Houston]

While the '41 model cars can be regarded as modern cars, it might be straining them to drive them at highway speeds today. The rear axle ratios were changed to lower values, as soon as the high speed highways (PA. Turnpike, etc.) began in 1940. Since you have a series 75 car, you probably have a rear end ratio of over 4:1. This makes the engine run at very high RPM. That year's axle ratios offered an "economy" ratio of 3.36:1 for the  cars, other than the 67 or 75. They offered an economy ratio for the 67 and 75 cars of 3.77:1, which was the standard ratio for all except the 67 and 75.

You might want to check the ratio of your rear axle, and if it's the regular one (4.11?), find a good 3.77 differential and carrier ass'y. and replace yours with it. A friend in this area has a 41-67, and I gave him a 3.77 pig for the car.He's ecstatic over the lower engine speed.

I wouldn't recommend putting a 3.36 pig in a 67 or 75. The car will be pretty doggy.

[Virgil Perkins #19943]

While the '41 model cars can be regarded as modern cars, it might be straining them to drive them at highway speeds today. The rear axle ratios were changed to lower values, as soon as the high speed highways (PA. Turnpike, etc.) began in 1940. Since you have a series 75 car, you probably have a rear end ratio of over 4:1. This makes the engine run at very high RPM. That year's axle ratios offered an "economy" ratio of 3.36:1 for the  cars, other than the 67 or 75. They offered an economy ratio for the 67 and 75 cars of 3.77:1, which was the standard ratio for all except the 67 and 75.

You might want to check the ratio of your rear axle, and if it's the regular one (4.11?), find a good 3.77 differential and carrier ass'y. and replace yours with it. A friend in this area has a 41-67, and I gave him a 3.77 pig for the car.He's ecstatic over the lower engine speed.

I wouldn't recommend putting a 3.36 pig in a 67 or 75. The car will be pretty doggy.

Doug,
Thanks for your reply. I agree with what you are saying about a 75 series, however miine is a 6019SF, with a 3:36 rear end. I even have a spare 3:36 that I pulled out of may parts car (the Red Roach). So, it's not that bad, but you sure can tell that is easier on the engine at 70 than at 85 or above, again that is according to the speedo, which I am sure is registering a somewhat faster than actual mph.
Cadillac, as you know, advertised that their product would do 100 mph in 1941, and for a time, I wanted to prove them right, but I am past that now. It did register 95 on the speedo, but I got to thinking about what might ensue if I had a sudden need to slow down or stop while that speed, and common sense has kept me from duplicating that speed test since. I am content to cruise at 65 to 70 and not worry about tickets or problems that the higher speeds may geneerate.
I am running a 4:11 in my '55 Chev convertible that I have had since 1956 and am getting ready to replace it with a 3:70, so as to enjoy the highway cruising more and buy gas less, not to mention lessening the rpm at higher speeds.
If I do wind up with a 75 series Cad, I will be looking for the standard rear end for it also.
Thanks again, VP