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MG Midget and Sprite General - Carb Differences

I am looking to buy an old set of carbs to refurb for my MKII

The original ones are AUD136.

What is the difference with the later ones AUD327 and AUD502?

Cheers

Tony
Tony Brough

Tony. Generally speaking, each vehicle had its own specification number. Your original specification was used on the 1098 and 1275 engines of certain years. But, the jets and the bodies of all the various carbs, within the general specification--i.e. HS-4, H-2, et al. were the same and the major differences were the piston springs and the needles. Thus, as long as the carbs are of the same type (HS-2 for your year) at most you would have to replace the piston springs and needles to use the carbs on your engine.

My book, "Tuning S.U Carburetters, 3rd Edition" only lists carbs by vehicle, and does not present a second table listed by specification number. If you know what vehicle the carbs came off of, it would be possible to look up what piston spring was used. (I suspect most of them used the same spring.) The only way to know for sure what needles are in a set of carbs is by physical inspection of the needles. Many have been changed, over the years, in search of greater performance, better fuel economy, or due to emissions testing requirements.

Les
Les Bengtson

x2, What Les said.

In answer to your question,
AUD136 = AN needle, Blue spring
AUD327 = AN needle, Blue spring
AUD502 = AAT needle (slightly richer), Red spring (stiffer)

the AN needle is a fixed type, and the AAT is a spring loaded type, both are interchangeable as long as the fixing screw and the brass guide are also changed with it.

I could not find what the difference is between 136 and 502, as all of the reference books I've got list the same parts in them (float, throttle disc, jet, etc.). I wonder if the difference is the 136 is without the vapor recovery tubes through the carb body, in front of the throttle disc, and the 327 is with?


Norm
Norm Kerr

Also, from mid '68, the crankcase breather was connected to stubs on the sides of the carb bodies, rather than to a PCV valve on the manifold.
Dave O'Neill 2

Tony
I have a set jetted for a 1275 in good condition that just need a good clean if your interested ?
rob at cornishconnectionpasty dot co dot uk
Rob Newt

Thanks for the replies and information.

Its good to know that apart from the ones with the stubs on the bodies that I can use others that are not the exact same spec.

I intend to change the needles and springs anyway.


Rob you have mail
Tony Brough

Tony. If by "stubs on the bodies" you mean the ports for the emissions control system, they are fully useable. You simply run a piece of hose between the two and it seems to have no effect on the running of the engine. I have been using such a set up on my 68 BGT for some years now because they were the only carbs available when I needed a set immediately. You could, also, plug the holes and not have to use a hose between the two. Should not be a significant factor except when bargaining over price. "Well, these will require extra work because my car does not need ones with these holes, so they are not work as much as a set of proper carbs."

Les
Les Bengtson

Nice tip Les :-)

Is that book still in print? if so do you have the ISBN

Tony

Tony Brough

This thread was discussed between 05/07/2011 and 07/07/2011

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