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Old 09-24-2019, 07:46 PM   #7
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Default Re: My 1st decent drive of Model A and discussion

Originally Posted by Synchro909 View Post
Good to hear you have finally gotten it out of the garage. I've been wondering how things were going.
IMO and experience, if you want to do trips like Alaska, you'd be a looong way better off putting in a counter balanced crank shaft and rods (invisible). Whether you run them on babbit or inserts, I don't think makes all that much difference. The weakest point in the bottom end is the middle main bearing so I pressure feed it but not the others. I'd also go for a head with higher compression than a police head. 6:1 sounds good to me. A mild cam is also invisible and makes a world of difference to these motors. You wouldn't believe how much!
With a motor like that and wanting to travel at the sppeds you mention, I think a higher diff ratio is a must. 3.54 at least. 5.5 tyres increase your overall gearing by about 5%. A 3.54 diff increases your gearing by about 6% (from memory) over the the 3.78 ratio. If you do both, you have 11% higher gearing with the advantage of more rubber on the road. At the same revs you would have been doing at 45mph, you would then be doing 50 which I think is enough in a car with poor (by modern standards) brakes, suspension and steering.
Another alternative is to go to a 3.27 diff. That will give you a gearing 15% higher than standard so you are in the same ballpark. 3.27 with the larger tyres gives you near enough, 20% higher gearing which is getting close to having an O/D (26ish%) in there but you can't shift down for hilly terrain or traffic without going back to 2nd gear (not recommended).
As you know, I have done plenty of long distance touring and would be glad to discuss this with you. I think you have my number.
If you have the $$, you can put in the Mitchel synchro cog house for easier gear changing. It cannot be distinguished from an original gearbox from outside and the closer spacing between 2nd and 3rd gears is a winner.
There are lots of options to mull over!

I've been mulling over things for quite some time! Just needed to see for myself what a stock A can really do.

The Model A crash box tranny is a pain in the a#% but I feel it's part of the car's character; so Mitchell syncro is off the list for me. If I had wife/kids wanting to drive the car it would make sense though.

I fear a 3.27 diff, or 5.50x19 bias with 3.54 diff, would not work well in mountainous terrain or if you wanted to do towing or you had four passengers in the car, even with a 50hp engine.

Actually, 5.50x19 bias gives slightly higher gearing than 3.54 diff, see:

I already have two BF Goodrich 5.50x19 bias tyres, I just need to fit them to wheels. Before buying two more I want to check to see if they fit the front of the car without hitting brake rods or whatever. If they don't fit to the front of the car I will run smaller tyres on the front. Note that the Nokia 5.50x19 bias are smaller than BF Goodrich. If Nokia were also too big for the front I could use 4.75/5.00x19.

The beauty of the 5.50x19 bias with 3.78 diff option is that if you wanted to you could have two extra wheels fitted with normal 4.75/5.00x19 tyres and change to those if you were, for example, planning on doing a long tour towing a trailer in mountainous terrain. So effectively, your car would be BOTH 3.78 and 3.54, changing rear tyres to/from 5.50x19 bias would determine which diff ratio you have.

You're correct about the building a new engine to suit my's just that the engine in my car now runs real nice; be a pity to take apart a good engine. Think I might do a compression check, and pull the pan and check condition of babbitt, really see how good it is.

Last edited by M2M; 09-24-2019 at 08:18 PM.
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