horsepower needs??

[MikeTaylor]

I recently purchased a '48 Tudor that's been converted to 12V and has an aluminum cross flow radiator but is otherwise stock. Planned usage includes daily (SoDak winters permitting) driving and reliable enough to jump in and drive to wherever the road takes me. Since purchasing the car, I've got the brakes, steering and suspension in top shape which leaves the engine and therein lies my questions.
1. With 3.78 rear gears, an overdrive system is a must for hiway cruising. I'd prefer an early '50's Ford/Merc column shift setup but that will require splitting the wishbone and I have no idea how that's done.
2. A/C is also a must traveling to the south or across the deserts to the west coast.
So, how much horsepower do I need to get out of this 59A flathead to pull 2.64 rear gears with the A/C on at 65-70 mph?

All thoughts/comments are welcome and my thanks for your time - Mike

[bart78]

Use a Columbia two speed rear end. If you are going to be doing that much driving. And you don't have to split the bones on the rear.

[Charlie ny]

Mike,
THEE simplest way is to stay with the 3:78's and get yourself a Columbia
rear end. I seem to recall that a Columbia drops a 3:78 to around 3:22. Columbias
are still relatively plentiful for the '46 - '48 cars.
My uneducated opinion is 2:64s are too high for Flathead.
A/C....=.....Vintage Air.....goggle them.
Charlie ny

[Vic Piano]

There are other options for overdrive if you don't want to go the Columbia route. Mitchell makes a modern OD unit that has gotten good reviews. You can Google Mitchell Overdrive or, I think that Mac's offers them in their catalog.

[Ol' Ron]

'd go with the Michell, less chance of problems after the initial installation. Find a set of 39-41 221 heads, mill for .050" piston clearance and clearance for the valve. This will boost CR about a point in a 239 engine.

[MikeTaylor]

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Ol'Ron - forgot to add - I'm going to rebuild the engine - pistons are already .030 over so thinking I might go to 3-5/16 and adding a 8cm merc cam in addition to bearings, valves, etc. The Mitchell has OD choices of 74% and 64% or final drive ratios of 2.8 and 2.41. Going that way I think I'd opt for the 2.8??
Mike

[Bruce Compton, Canada]

I agree, the Mitchell is the way to go. They make a great overdrive, but did the math wrong so believe me, go with what they call their "36%", and the lever control. I tried both of their ratios in my '36 coupe with a 3.78 rear and a 59L block with a Merc crank. Perfect combination with lots of torque and overdrive cruising comfort. Good luck : Bruce

[supereal]

The OD in my '47 gives a 33% reduction with a 3:78 rear end. It is a bit tall for driving below 40 mph, but really does the job on the highway. The Columbia axle is nice, but good ones are hard to find. If you do find one, be sure that all the controls are with it. I just saw an ad offering just the controls, including the speedometer changer, for $2,500! By the time you find the axle to so with the controls, and have it "bullet proofed", big money is involved..

[blucar]

From my point of view, the Columbia O/D with a 3.78 axle ratio is very hard to beat, they require no alteration to the vehicle and are very trouble free..
I have a '42-48 Columbia under my '36. The car came with a Columbia which was installed when the car was new.. I did not care for the early Columbia's so I switched to the later model style..
My engine is a well built 59AB, trans is a '47-48 Merc 28 tooth.. During the 61 years I have had the car... yes 61 years, I have driven it over 94k throughout seven of the eleven western states.. I have driven the car in blinding blizzards in Idaho, Wyoming and Utah.. I have also driven it in poring rain and blistering desert heat in Nevada and Southern Calif..
A third option for an OD in an early Ford is a Ford C4.. Speedway has the conversion parts.. I know a couple of guys that have done this conversion. The rear end does have to modified to an open drive line which either requires splitting the wish bones and or changing to parallel rear springs.
The one point that most people overlook with an OD is the rear end gear ratio.. Historically the axle ratio is numerically lower for an OD, i.e. a '59 Ford pickup is usually 3.72, with an OD, it is 3.89..
My brother has a very nice '54 Chevy BelAir with a 350 V8, and 350 TH trans.. The axle ratio is 2.90 +/1.. A guy talked my brother into putting a 2004R AOD trans in the car. Ruined a good car, he has to drive the car in 3rd gear all the time because it is over geared, even on the highway.. He is saving his money up to re-gear the axle to something around 3.24/3.26..
Modern cars with AOD transmissions run at 2,100/2,300. RPM's at 65 mph. That seems to be an optimum range for highway use..

[Ol' Ron]

The 3 5/16 by 3 3/4 flathead is my favorite engine, giving 258 ci, and the 81a heads would put that near 8;1 cr. Using the 8cm cam would allow the use of the SBC distributor with good power and economy. Good luck

[AnthonyG]

Hi Mike, I don't think I saw anyone mention it, go bigger on rear tires to reduce highway speed rpm. I went from stock 600 X 16 to 750's and it made a big difference at 60 mph. Brought rpm down considerably. Not as much fun on the take of but not bad.

[blucar]

Over-tiring, i.e. 750/820 tires in lieu of a proper size tire on a vehicle is an "old school" quick fix to improve gearing issues.. The only problem is that the vehicle is trapped into having only one gear ratio, which for daily street driving is to high..
Had a family member years ago that compounded the problem by installing 26 tooth Lincoln gears with 820 tires.. Stock engine in a '40 Ford sedan..
An OD system, be it a Columbia or an Aux trans unit (Mitchell) provides the best of two worlds, good gearing for daily street driving and great highway gearing, especially if hilly areas are encountered..
I've had several Ford vehicles with the Borg-Warner OD units attached to a Ford 3 spd trans, they work great, especially with the freewheeling feature, allows shifting with out the clutch at speed under 35 mph. Unfortunately the early X member frames and traverse springs requires a lot of modifications in order to mount an OD trans into them..
I have a '39 Plymouth with a V8 and a AOD trans, a pleasure to drive. I'm just finishing up with the installation of a '97 5.7 V8 and 4L60 AOD trans in my '64 Chevy C10 pickup.. It should also be a nice ride...
"Nothing is Impossible, some things just take longer and are more expensive"...

[Bassman/NZ]

Wow, Blucar.... 61 years must be a record here......
I'd go with the Mitchell too, cheaper and possibly better than rebuilding a Columbia, and like others have said, no mods needed.

[bart78]

You can adapt a Borg Warner R10 to a torque tube can't you. What do y'all think of those?

[AnthonyG]

Bill, blucar, I don't disagree too much and do agree the Columbia or Mitchell is a fine choice but lot's of Barners go with the 600 X 16 on the front and 700 to 750X16's on the rear cause it looks cool too. We don't give up too much in the lower gears and no need for the OD. I rarely pedal to the medal mine and really don't notice significant difference in my acceleration with the 750's. I have run my '35 with a '39 tranny and a 4:11 rear and 750's for hundreds of miles on and off the highways always comfortable getting into traffic and keeping up with traffic.

[Mike B]

Originally Posted by blucar

A third option for an OD in an early Ford is a Ford C4.. Speedway has the conversion parts..

Isn't the C4 just a 3 speed auto?

[AnthonyG]

C4 conversion is a nice set-up but requires open rear, torque tube and wishbone rear go away and replace with usually a 9" ford rear and conversion to leafs / tube shocks on both sides.

[Mike B]

But still 1 to 1 rear drive, other than being an auto and using a bit more power, what advantage is there?

[40cpe]

Maybe someone who as done it will jump in, but an auto lets you have a higher rear gear because of the torque converter. Low 3s ratio or even high 2s. Then there is the converter slippage, but I suspect the net is a gain over a 3.78 standard.

[Mike B]

Originally Posted by 40cpe

Maybe someone who as done it will jump in, but an auto lets you have a higher rear gear because of the torque converter. Low 3s ratio or even high 2s. Then there is the converter slippage, but I suspect the net is a gain over a 3.78 standard.

I wouldn't think so...I have a lockup converter in my Camaro, and when it locks, the RPMs drop about 100-150 RPMs.