3.27 Gear without an Overdrive

[Ruth]

I'm curious, does anyone have a 36% Mitchell O/D? How does it compare to the 26% O/D. I have the 26% and like I have said before, I use it more like an underdrive, keeping the Mitchell in O/D most of the time and downshifting the Mitchell as needed for hills.

[updraught]

Maybe fit a tachometer and work out what range the engine pulls in to start with. I think this is what Ford would have done.

[Model A Ron]

Originally Posted by Ruth

I'm curious, does anyone have a 36% Mitchell O/D? How does it compare to the 26% O/D. I have the 26% and like I have said before, I use it more like an underdrive, keeping the Mitchell in O/D most of the time and downshifting the Mitchell as needed for hills.

Mitchel will tell you the 36% was made for the 4.11 gears.

4.11 with a 36% OD is the same 3.00 to 1 that you get with the 3.78 and 26% OD

[Model A Ron]

Originally Posted by Ruth

I'm curious, does anyone have a 36% Mitchell O/D? How does it compare to the 26% O/D. I have the 26% and like I have said before, I use it more like an underdrive, keeping the Mitchell in O/D most of the time and downshifting the Mitchell as needed for hills.

Ruth
How do you drive your Mitchel?

I start in first, second, Second high, third, and then third high. Are you doing the same?

[BRENT in 10-uh-C]

Originally Posted by Benson

Do the 3.25 cars that you mention have reground camshafts or Stipe IB330 or IB340 cams?

I wonder if reground cams raise torque curve too high to work with the lower RPMs of a 3.54 / 3.25?

Yes, I pretty much use IB330 camshafts exclusively.

Many reground cams back in that timeframe were refurbished with masters of unknown origin. Additionally, the centerline of each lobe can be all over the place in relation to the other 3 lobes as they were one cheaply.

With regard to taking away power, when the heal of the camshaft is ground to allow the nose to gain more lift, the grinder must generally must remove material from the area 90° from the heal, and 90° from the tip of the nose which decreases duration. This is a bad thing. Just because the lift is the same number, a smaller degree of duration does not allow for volumetric efficiency to get the air/fuel into the cylinder. A Model-A/B engine was originally designed as a torque engine. It was never intended to be an engine that needed to be revved to make power. Many of these so-called "touring camshafts" are pitiful when it comes to improving on what Ford had designed originally.

I would venture a guess on your engine, that a cam change to an IB330 would totally change the driving characteristics of your vehicle. Also knowing what carburetor you are using might tell us more too.

[Ruth]

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Originally Posted by Model A Ron

Ruth
How do you drive your Mitchel?

I start in first, second, Second high, third, and then third high. Are you doing the same?

No, I start in 1st high, to 2nd high, to 3rd high. I leave it in overdrive most of the time. I shift out of O/D only when I have to on a hill that I can not pull in 3rd over.

I have shifted your way but find just leaving it in O/D works best, for me.

[Model A Ron]

Originally Posted by Ruth

No, I start in 1st high, to 2nd high, to 3rd high. I leave it in overdrive most of the time. I shift out of O/D only when I have to on a hill that I can not pull in 3rd over.

I have shifted your way but find just leaving it in O/D works best, for me.

Ruth
I do appreciate the feedback. A local member of my club drives this way as well and by starting off in Mitchel High (if your running 3.78 gears) is the same as having 3.00 to 1 gearing.

I tried this and found it to be a very slow once I got into 3rd. I spoke to the man in my club doing this last night and he told me to ride out 2nd a bit longer and I should be fine.......I think both you and this man are correct. At what speed do you shift from 2nd high to 3rd high? I plan on taking a second run with my Mitchel in High later on today.

Like I said above this method is like driving 3.00 to 1 gearing and is a 26% overdrive from standard gearing. In my 31 Victoria Project I think I should be fine running 3.27 gearing that would offer 15.5% full time overdrive over standard gearing.

Using a 3.27 gives you about 60% of the benefit of a 26% Mitchel with the 3.78. The only down side I see is you do not have Mitchel 3rd low to drop down into on hills if needed

[Ruth]

Originally Posted by Model A Ron

Ruth
I do appreciate the feedback. A local member of my club drives this way as well and by starting off in Mitchel High (if your running 3.78 gears) is the same as having 3.00 to 1 gearing.

I tried this and found it to be a very slow once I got into 3rd. I spoke to the man in my club doing this last night and he told me to ride out 2nd a bit longer and I should be fine.......I think both you and this man are correct. At what speed do you shift from 2nd high to 3rd high? I plan on taking a second run with my Mitchel in High later on today.

Ron, I would like to answer that question but unfortunately my speedometer reads quite low (after being rebuilt by a well known rebuilder on here). Next time I'm out I can check my GPS for you, but that is not going to do you any good right now.

When I am accelerating I shift at ~2100 rpm but normally don't like to rev it that high.

My car is a heavy '30 Town Sedan so I imagine your Vicky will do quite well with the 3.27's. The beauty of having the Mitchell in the mix is the synchromesh for the down shift.

A friend has a Mitchell O/D and a Mitchell synchro trans. What a nice combo, but a little too spicy for me. Maybe I should start collecting beer bottles from the side of the road??

[Ruth]

Duplicate.

[Model A Ron]

Originally Posted by Ruth

My car is a heavy '30 Town Sedan so I imagine your Vicky will do quite well with the 3.27's. The beauty of having the Mitchell in the mix is the synchromesh for the down shift.

Ruth
I love the Mitchel in my 29 and if I had an unlimited budget the Victoria would get one as well. My problem is the Victoria has 4.11 gearing so my cost would be $2400 for the Mitchel plus the cost of 3.78 gear. By dropping to the 3.27 gear I get 60% of the overdrive Benefit and get to use that money on the restoration.

Whenever you get a chance to get a GPS speed when shifting from 2nd high to 3rd high just let us know......this is all good information so thank you.

[J Franklin]

4.11 and overdrive is the best of both worlds.

[Model A Ron]

Originally Posted by J Franklin

4.11 and overdrive is the best of both worlds.

With a 4.11 you would have to drive your car in Mitchel High. I have a 4.11 in the Victoria and that's just tp low for me.

[Keith True]

I have a 31 coupe with 3.54's and a 26%Mitchell OD.Works great.The only known for sure mod to the engine is a BF head.The previous owner had put the 3.54's in and the head on,I put the Mitchell in.Most of the time I forget the OD is in high and just drive it.I've had two BW OD 33%setups,they were just a bit too much.I have a 30 RPU with just 3.54's,B cam,BF head,B carb,i can climb mountains with that.I am thinking about putting some 3.27's in it.

[Model A Ron]

Originally Posted by Keith True

I have a 31 coupe with 3.54's and a 26%Mitchell OD.Works great.The only known for sure mod to the engine is a BF head.The previous owner had put the 3.54's in and the head on,I put the Mitchell in.Most of the time I forget the OD is in high and just drive it.I've had two BW OD 33%setups,they were just a bit too much.I have a 30 RPU with just 3.54's,B cam,BF head,B carb,i can climb mountains with that.I am thinking about putting some 3.27's in it.

If you put a 3.27 in with a 26% Mitchel that's the equivalent of 41.5% overdrive with the standard 3.78. Are you sure you do not have a V8 in that thing

[J Franklin]

Originally Posted by Model A Ron

With a 4.11 you would have to drive your car in Mitchel High. I have a 4.11 in the Victoria and that's just tp low for me.

That is one good idea and think of the hills you could climb.

[Benson]

Originally Posted by BRENT in 10-uh-C

Yes, I pretty much use IB330 camshafts exclusively.

Many reground cams back in that timeframe were refurbished with masters of unknown origin. Additionally, the centerline of each lobe can be all over the place in relation to the other 3 lobes as they were one cheaply.

With regard to taking away power, when the heal of the camshaft is ground to allow the nose to gain more lift, the grinder must generally must remove material from the area 90° from the heal, and 90° from the tip of the nose which decreases duration. This is a bad thing. Just because the lift is the same number, a smaller degree of duration does not allow for volumetric efficiency to get the air/fuel into the cylinder. A Model-A/B engine was originally designed as a torque engine. It was never intended to be an engine that needed to be revved to make power. Many of these so-called "touring camshafts" are pitiful when it comes to improving on what Ford had designed originally.

I would venture a guess on your engine, that a cam change to an IB330 would totally change the driving characteristics of your vehicle. Also knowing what carburetor you are using might tell us more too.

Brent

Thanks for your thoughts on cams.


That answers my questions. I will replace my present regrind with IB330 I have and then reevaluate the 3.78 / 4.11 idea after I restore low end torque.

From your experience I might not have to change to 4.11s.

I have used 4 or 5 different Bert's Zenith rebuilds and they all work the same.

[Keith True]

The pickup that I want to put the 3.27's in doesn't have a Mitchell,just the 3.54's.I have a coupe with 3.54's and a Mitchell.

[Model A Ron]

Originally Posted by Keith True

The pickup that I want to put the 3.27's in doesn't have a Mitchell,just the 3.54's.I have a coupe with 3.54's and a Mitchell.

Do you think the pickup would be better with the 3.27? I would think that it pulls without any issues with 3.54's.

Have you ever driven the coupe with the Mitchel and 3.54's in high from a stand still to 40 or more?

[Keith True]

I really only use the pickup now if I am going somewhere for the day,and have to carry a bunch of stuff with me.Chairs,coolers,little grill,etc.I just like to keep my revs down on anything.I ran a 58 HD panhead with the tallest set of sprockets I could come up with for it.65 MPH was a high idle.Of course that had the brute low end torque to carry it off.I drive the coupe with the OD in high more than I do in low.I take off with it in low,and when I'm on a main road and shift it into high,then forget to take it out again.I will remember to take it out when I'm in a line at a drive up window.

[Hotrodfil]

Originally Posted by Model A Ron

I would like to hear from people who are running a 3.27 rear end without an overdrive. Would you get a 3.27 if you had to do it again?

Running one in my Coupe. Love it. Tempted to fit my close ratio gearbox too.

600 mile round trip to race at Pendine. Mainly country lanes up hill and down dale, with a few forays onto bigger roads, keeping pace with a friend in his 32 roadster. Running 50-65moh most of the time.

Averaged 25mpg (proper sized gallons too) and hit 74mph on the beach.

Spec on the engine. Ported diamond B block, modern stock sized valves, stock bottom end, Stipe 340 cam, Brierley head, Burns manifold and a single 97.

Stock height T Coupe on an A chassis, B front axle, '35 brakes, stock A transmission - and a 3.27 final drive...

Oversize tyres too. 4.50 x 19 Blockleys on the front and 6.00 x 19 Michelin DR on the rear.

Dunno if you can tell but - couldn't be happier with the set up.