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Transmission / OD dilemma

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F Schreiber

Senior Member
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Looking for input from folks on what to do here.

I have 1960 (early) BN7 I plan on restoring. Transmission does okay, (and a whine in it or OD there somewhere). OD unit takes a while to pull in and slips or pops out when good and warm. I planned on rebuilding both so they would be 100%. I knew my car had the engine swapped out when I got it. Today I pulled the tunnel cover off and find out its got a 100-6 transmission and OD unit. Trans is AEC3174 serial B5483. I can't find reference for that but I think its 100-6, and O/D unit is 28/1447/006377

While I have thoughts of trying to keep car as original as I can, I need to decide whether to try and find the correct trans and OD unit. To keep the existing, or maybe go with a centershift. My looking at the the ratios, it looks like the finale ratios to the ground for the 100-6 and the BN7 are close, the 100-6 looks a little wider range, but that might be splitting hairs. I plan on installing the BJ-8 camshaft. I also thought about going with the HS6 or DH8 carbs, but I might keep my HD6's. Would any of those things make a performace , driveablility or reliability difference? Would the correct trans and OD be better that the 100-6 set up. I am thinking if I am going to rebuild them both, maybe I should rebuild the correct ones.

And does anybody have the the correct trans, or overdrive they want to sell. ( I think that would be AEC3524, and 22/3009). I am fixing to put an add in the forum classified. With people converting to 5 speeds doesn't that make some of these available?? ( I don't think I want to go to the 5 speed, I like the OD set up.)
 
IMO you'd be better off to stick with the 28% OD whether you go to a center shift or not - better cruising speed. A friend has one on his BN6 with bored/cammed 3000 motor. With the 3.54 axle it does 80+mph at 3000rpm. The Healey has plenty of torque for this setup. Several of us have installed DWR 8 278* cams and in my opinion it is superior to the BJ8 cam. Pulls from 1000 rpms and is gun-drilled for oiling.

HD6 carbs are great. You might want to get them re-bushed. See Tom Bryant - https://thosbryant.wordpress.com/category/su-carburetors/

I like the simplicity of the HD6 and the richness is easier to adjust from the side with a screwdriver, rather than having to reach underneath with the special wrench.
 
Thanks for the feed back. Thats good support for keeping and rebuilding what I have. And keeping the carbs I have. My rear end is the 3.909. So from you feed back that would add more fuel to the case for keeping the 28 overdrive. So you don't figure I would get much more power out of the bigger carbs? And what's the down side of the cam you mentioned, would it be rougher idle than what I have?
 
F Schreiber said:
Thanks for the feed back. Thats good support for keeping and rebuilding what I have. And keeping the carbs I have. My rear end is the 3.909. So from you feed back that would add more fuel to the case for keeping the 28 overdrive. So you don't figure I would get much more power out of the bigger carbs? And what's the down side of the cam you mentioned, would it be rougher idle than what I have?
Click to expand...

Once I got my HD8 carbs bushed by Bryant, my car idles nearly perfectly smoothly at 750rpm. I got a really good deal on my HD8s but am not sure they really made any difference in the overall power. I added my headers and DMD manifold at the same time, keeping the HD6s, and those made a seat-of-the-pants difference. Don't recall much difference when I swapped the HD8s.
 
F Schreiber said:
Whats DMD manifold??
Click to expand...

screenshot.1748.jpg


Sold by the Healey Factory in Australia.
 
I will look into that. I had thought about putting headers on, so If I am going to to that, might as well do the inlet too. That's not that far from staying original, right??
 
One thing I am wondering is since I have a non syncro first gear, will that high an idle give me trouble getting into first gear. I have not drove my car alot, but its hard to get into first at a stop, by carbs need re-bushing, and I have to blip the throttle to get it to idle down, and that helps.
 
With the clutch pedal depressed pull the shifter partially into second, then push it into first--there will no longer be a crunch.
 
Second gear , then to first , it will never crunch .
 
I Have HD8 carbs on my BJ7. i think with the BJ8 cam & the HD8 carbs are worth it. I know other cams could even be better as Steve as stated. I would keep the trans and OD that you have. No real advantage to changing them unless you do a 5 spd which has its issues too. But one healey trans or Od to another isn't going to be that noticeable. I think all the Healey parts from all the years are equally reliable, it is primarily contingent on how well you build them. As far as the effect of having the feel of an original Healey, as long as you don't put a non-healey engine and trans in it will feel like an original Healey. Good Luck and Happy Healeying.
 
Thanks for the feedback. That makes me feel even better about keeping the existing trans & OD. When you did the carb s and cam, did you do them one at a time or separate.
Another thing. I will always keep the old carbs and inlet manifold. So I can always go back.
 
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