Mitchell overdrive

Lawrie

Lawrie

Well-known member
Any one using the Mitchell and using the 3.54 rear end gears,
I have one coming for my 28 ccpu ,and would like to know how strong an engine you will need with the 3.54 rear end gears.
Lawrie
 
Lawrie, I considered a 3.54 gear set with my Burtz engine and decided to wait. I'm happy I did. In fact, I am beginning to question whether I need the O/D at all with the new engine. It revs so freely and smoothly that if I were cruising at say, 55 mph in O/D, the car is now happy in ordinary 3rd gear and "singing" in a higher key at that speed. I have a virtually new 3.54 set on the shelf and if I don't use them in another of my cars, they will likely sit there for who knows how long.
How strong an engine? There have been a couple of times when I have forgotten to take the car out of O/D when I stopped and taken off in high first with the camper behind. Sure, it didn't make my cheeks go baggy when I pressed the accelerator but it did it. That engine was not as powerful as the one in your P/U but might have had more grunt t the bottom end.
A 3.54 diff and O/D is a pretty high ratio - about the same as using 5.25X21 tyres on the rear of a 3.78 diff. I run that on my tourer and it gallops along. Your engine will handle it easily.
 
Yes , no drama as I have a set of good original 3.78 gears.
I ment to tell you, you know you would be able to get .001 or .002 under bearings.
 
I have a 30 Tudor with a AER touring engine with 5.5 head,V8 wheels 600-16 tires,3.54 gears..I like this combination very much.Not to many steep hills in my area but has no problem with them.I would have stayed with 3.78 gears with a stock engine.
 
I am very happy with my Burtz engine, Mitchell overdrive, and 3.78 rear end. In overdrive it is like having a 3.0 rear end (about). I use second overdrive a lot in the hills were I live. I think 3.54 gears would be too tall.
 
Lawrie,
Running 3.54 gears and a 26% overdrive gives you about a 2.60 final gear. I run a 3.78 gear with a 26% Mitchell and is a great combination with a stock engine. Mine would not like any taller gears. Cruises nice at 50 mph plus. Dale
 
I went to put a Mitchell in my coupe,and found it had 3.54's.I put it in anyway,and it performs fine.I forget and drive it around a lot in high.I do find myself touching 60 quite a lot.Not sure how accurate my speedo is,at some point it will interest me enough to check it out.The previous owner thought it had a Brumfield head on it,at least that was what he was told when he bought it.It pulls fine.
 
Getting ready to do the Mitchell and have wondered about the 3:54 gears with a stock engine? I just picked up my engine and am debating putting the 6.0 head on it or just leave it stock? I have another rear end that I need to pickup this week and I think it's been gone through and is probably 3:78, so just need to decide if I need the HC head or just leave it stock with the overdrive and 3:78 gears?
 
MrBruce said:
Getting ready to do the Mitchell and have wondered about the 3:54 gears with a stock engine? I just picked up my engine and am debating putting the 6.0 head on it or just leave it stock? I have another rear end that I need to pickup this week and I think it's been gone through and is probably 3:78, so just need to decide if I need the HC head or just leave it stock with the overdrive and 3:78 gears?
Click to expand...

There’s no reason other than the cost of purchase to not use a high compression head.
Use a Snyder’s head and B carb if you want to look stock.
It’s a noticeable difference in performance.
 
OK , thanks for the info, I will take a chance and leave the 3.54 in and see how it goes, my engine is good, 6.2 head, 97 carb, and a stipe cam , its a Burtz engine .
Its only a few days work to change out the 3.54 gears for the 3.78 if I,m not happy with them
The Overdrive is a few months away , but will keep you posted how iy=t goes when it arrives.
Lawrie
 

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Lawrie said:
OK , thanks for the info, I will take a chance and leave the 3.54 in and see how it goes, my engine is good, 6.2 head, 97 carb, and a stipe cam , its a Burtz engine .
Its only a few days work to change out the 3.54 gears for the 3.78 if I,m not happy with them
The Overdrive is a few months away , but will keep you posted how iy=t goes when it arrives.
Lawrie
Click to expand...

Lawrie, with that set up and on roads like that, please don't go past Mach 1.
 
I have a 1930 Town Sedan, and had a Mitchell OD installed about 14 years ago, along with the 5.5 HC head, and it has the 3.78 rear end. The 4 doors are the heaviest Model A’s, and I would not recommend the 3.54 with the Mitchell, without some serious engine mods. Mine pulls the OD nicely…..very glad I did the 5.5 head too.
 
Synchro909 said:
Lawrie, I considered a 3.54 gear set with my Burtz engine and decided to wait. I'm happy I did. In fact, I am beginning to question whether I need the O/D at all with the new engine. It revs so freely and smoothly that if I were cruising at say, 55 mph in O/D, the car is now happy in ordinary 3rd gear and "singing" in a higher key at that speed. I have a virtually new 3.54 set on the shelf and if I don't use them in another of my cars, they will likely sit there for who knows how long.
How strong an engine? There have been a couple of times when I have forgotten to take the car out of O/D when I stopped and taken off in high first with the camper behind. Sure, it didn't make my cheeks go baggy when I pressed the accelerator but it did it. That engine was not as powerful as the one in your P/U but might have had more grunt t the bottom end.
A 3.54 diff and O/D is a pretty high ratio - about the same as using 5.25X21 tyres on the rear of a 3.78 diff. I run that on my tourer and it gallops along. Your engine will handle it easily.
Click to expand...

So can I ask....what if you never had an overdrive in the car behind your Burtz? Do you think you would eventaully snap a rod? With pressurized oiling on a scat crank don't you take the dipper tray out, and the rod caps have no dipper?
 
Gene F said:
So can I ask....what if you never had an overdrive in the car behind your Burtz? Do you think you would eventaully snap a rod? I don't think snapping one of these rods is going to happen under about 6,000 revs. With pressurized oiling on a scat crank don't you take the dipper tray out, and the rod caps have no dipper? It depends which rods you are using. Unless the crankshaft were drilled for oil to the rods, the dipper tray would stay in there and the dippers on the rods would supply the oil to the big ends. In the Burtz engine, the crank is drilled so the rods are pressure fed While the dipper tray in theory would not be required, it is recommended that it be left there so that the rods will throw up a good oil mist to help lubricate other things like bores and valve gear.
Click to expand...
My response is in red.
 
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