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Carburetors for a 1275cc Engine

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jkclassics

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I'm having a machine shop clean up and reassemble a 12CD engine to replace my '60 BE's tired 948. I plan on using HS2 carburetors; I currently have two sets, AUD73 and AUD136, which both need some work. Before I spend time on them, I'm wondering if either is the best fit for this engine or if I should be looking for something of a later vintage.
 
I have HS2s on my 1275. Work perfectly. I cannot help with th specific AUD number though. It sort of applies to original vacuum units and needles depending on where the car was going to be sold (emissions)
Any Modifications or just a simple refresh??
 
SU.PNG
I'm running AUD136's on my 1275 which work fine for me. Had not heard of the AUD73's but found chart below that they were on early 1098cc sprites.
 
Joe Schlosser said:
I have HS2s on my 1275. Work perfectly. I cannot help with th specific AUD number though. It sort of applies to original vacuum units and needles depending on where the car was going to be sold (emissions)
Any Modifications or just a simple refresh??
Click to expand...

No modifications, just a going over to ensure everything was OK and fixing anything that wasn't.
 
Thanks for the chart. I knew the AUD73s were originally fitted to the 1098cc engines. They're in much better shape, though, than the AUD136s I have, which are in need of a major rebuild/restoraion. Based on my engine number, it seems like the later model carburetors might be better suited; just can't determine exactly where the 12CD engine fits into the scheme.
 
For 1275 engines, I like the one with the vacuum ports for emissions. They work well in place of a PCV system.
 
12CD with the thick flange is the one to have, or the 12V.


12CC - Austin Healey Sprite Mk IV/MG Midget Mk III, 1967, 1275CC - MOWOG/"Engine" Green/possibly also the Light Green hammer finish (all "Thin Flange" blocks)


12CD/12CE (home market)/12CJ - Austin Healey Sprite Mk IV/MG Midget Mk III, 1968-1971, 1275CC - Light Green hammer finish - All emission controlled/evaporative loss engines (except 12CE)


12V - MG Midget Mk III, 1971-1974, 1275CC - Black


Here are the details of the carbs as well for all Austin Healey's. Looks like the main difference is the needle selection. Cheers.

SU Carb details.jpg






jkclassics said:
Thanks for the chart. I knew the AUD73s were originally fitted to the 1098cc engines. They're in much better shape, though, than the AUD136s I have, which are in need of a major rebuild/restoraion. Based on my engine number, it seems like the later model carburetors might be better suited; just can't determine exactly where the 12CD engine fits into the scheme.
Click to expand...
 
I have an old mini with a 1380, basically a 1275 bored out. I put 1.5 inch dual carbs on the engine and it has a flood spot at about 1/4 throttle. I have a 280 cam in the engine. Once you get into the 3000rpm, it just screams! So I would not recommend larger carbs. I put a air/fuel gauge into the car. Sensor into the exhaust manifold. This is very useful to tune the car and see what is going on as you use the throttle.
PS: I am on my 12th set of needles to get around the flood issue, but although I have seen improvement, it has not gone away. Once you learn to drive it, the carbs are not an issue. Slow pedal, not mashing it to the floor.
Jerry
 
JK
All HD2 Carburetors are the same except for two items, the needle and the spring. I assume that you will be taking off all the emission stuff that came with the cars built after 1968. Air pump, tubing, plug the heads and such. All the part numbers (AUD) for the carbs were for the emission control engines so you need to start at the beginning
For your plain stock 1275, you mentioned that you were not modifying it, the Vizard book gives a Red spring and E8 needles. After a good clean and installing the right needles either sets of your carbs should work great.
Talk to Dave or one of his people at APT on California to zero in on needles after your first go around but you are probably ok with the Vizard selection
 
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