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TR2/3/3A Need Help With Carb ID On My TR3B

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M

mxp01

Jedi Warrior
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All:

I have a TR3B. It does have SU carbs. I thought, and still kind of believe, that they are HS6s. However, the needles I purchased from Moss, but they didn't match the size in my carb. Upon further examination the number on my carb is AUD 505. Can anyone tell me the version of carb that I have?

Thanks,

Mike
 
All:

A Google search indicates that the number (AUD 505) is an HS6 for a special tuning MGB for a 1798 engine used from 1969 onward. However, when I go to the Moss catalog under MGBs they only list an HS-4 carb. Does anyone know anything about these carbs and where to obtain parts?? I'll also post on the MGB forum to see what I might learn.

Thanks,

Mike
 
mxp01 said:
All:

A Google search indicates that the number (AUD 505) is an HS6 for a special tuning MGB for a 1798 engine used from 1969 onward. However, when I go to the Moss catalog under MGBs they only list an HS-4 carb. Does anyone know anything about these carbs and where to obtain parts?? I'll also post on the MGB forum to see what I might learn.
Click to expand...
MG had a factory competition department, similar to the one Kas Kastner ran for Triumph. Larger carbs were one of the upgrade items for getting more power (in combination with other changes like higher compression and more aggressive cam profiles). According to the version I found, 1-3/4" SUs were used for Stage 3 & Stage 4. Stage 5 used a pair of Weber 45 DCOEs, while curiously enough, Stage 6 went to 2" SUs.

However, I wouldn't assume that your carbs still have the same needles (plus jets & springs) used in the MGB application. Changing needles and springs is a normal part of fitting SU carbs to modified (or different) engines, so whoever used those may well have found a different combination that they thought worked better. You need to identify what you have before you can replace it; and there are roughly 200 different needle profiles listed in my book just for .100" jets (.090 and .125 jets were also used and might be found in your carbs).

Edit: Sometimes you can find three letters or numbers stamped into the needle where it fits into the piston, to identify the needle. If not, you may have to measure at each of the up-to-sixteen stations and match what you find to one of the SU needle charts.
Eg, https://www.teglerizer.com/suneedledb/
 
TR3driver said:
Perhaps I am missing something. When I click on your link, I see AUD 209 and AUD 284. No AUD 505 ??
Click to expand...

I'm thinking the same. A key issue is that the needles in my car have a spring that attaches to the top. To support the spring the top has something like a collar on it. The needles I received lacked this collar and would not fit properly/securely in the bottom of the piston.

Mike
 
Yeah, the spring loaded needles were a later development, done primarily for emissions reasons I believe. Having the spring means the jets don't have to be perfectly centered as they do with the hard mounted needles.

However, the Burlen site shows a fixed needle for AUD 505, so I'm thinking someone has also changed the pistons to use spring loaded needles.
 
Ooops you are correct S.U. 505 were used on MGBs

M.
 
When I was trying to match up some spring topped needles with a set of HS6 carbs, I contacted Joe Curto and he was able to advise and supply some choices.
Charley
 
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