Hi team.
I've found a reasonable Amal 276C/1B. It has no jet block in it.
I also have a couple of other 276'
One jet block has 30T stamped on the bottom' and 39 on the top... Is this compatible with the spec for the 276C/1B?

Thanks in advance!

https://ibb.co/kX11mw0

The Amal list quotes a number 45 for an M20. I know that one of those numbers denotes the "flow rate". Ron

click to expand.

email (option): ronpier@talk21.com

AHH OK thanks Ron.Is that list available online?

I've found it impossible to relate the stamped markings on het blocks to any numbers in the Amal documentation. I took this photo some time ago and it shows, from left to right, a Type 76 jet block (stamped "30"), A BSA Type 276R block (from an A7, I think) and a Norton Type 276 with variant pilot air facility (both stamped "30T").



The list that Ron has posted shows a system of numbering that clearly relates to the inlet bore size. "45" is the code for a 1" bore instrument. Why they didn't stamp that on the block rather than making it necessary to get the calipers out is a puzzle !

It would seem that there are a limited number of variables which have to be correct when considering if a jet block can be used.

1) Overall size - It has to be a 276 size.
2)Bore size - For the M20 it needs to be 1"
3)Pilot air facility - For BSA it should have the single large hole on the inlet side to line up with the slot in the mixing chamber.
4)Throttle slide adjusting screw must be on the correct side. I believe handed bodies were produced for some twins.

Ok a BSA M20 has a jet block marked 45 on the top and 30 on the bottom. 45 denotes one inch, 51 denotes one and one sixteen. 15/16 is stamped 39. On a 276 you have left and right handed jet blocks and then the Norton jetblock with the two holes at the front. I have seen guys file the top of the jet block to suit a different handed body to allow the slide adjuster screw to work but the holes in the jet block will not line up with the body holes.

I was hoping you'd chip in John. Typical strange numbering from Amal. I assume then that the number on the bottom is the flow rate, but I've no idea how the metering is decided?

That is the 1939 list Mike I also have the 1940-54 list which doesn't give quite as much information. If you send me your email, I can send you a PDF file

Ron

email (option): ronpier@talk21.com

Thanks John.
So of the 3 carb bodies I have all are stamped 30T on the bottom.
The top stampings are 39, 28, and one possibly 28.
Oh well .... I'll keep my eyes open around the jumbles for a 45 then.

The knowledge in this group is amazing thanks so much👌

Hi Rob.

Email is mike-dodd@hotmail.com

This kind of stuff is brilliant,
I have a plan for a big trip in mind for my M20 and part of the plan is to know my machine inside and out. I'm not a mechanic so I'm learning as I go.
Many thanks👍

28 is for 13/16 275 smaller type carburetter. 58 is for bigger carburetter 1 amd 1/8.

Thanks John. I'll keep looking.... I see Amal are selling new 276C/1B's.........