Alloy Barrels

Does anyone have any experience with these from British Cycle Supply?

I don't know how good or bad they are, but they look like the ones Norvil in Staffordshire were making. I saw a set in their shop once upon a time, & they are they are the same shape as standard 850 iron barrels.

There look to be no airflow holes between the cylinders.
Is that of any consequence. ?

Have you asked if they're in stock? I inquired a couple of years ago when I saw that picture on their website and they had none.

Never had a set and would not use them. However I hear they give a few problems such as....
Lack of airflow between the cylinders causing the bores to distort causing rings to not seal correctly. If not required in the first place why did Norton incorporate a gap between the cylinders when it must of increased the cost of patterns and castings.
Special through bolts are required because the alloy barrel expands at a greater rate than the cast iron lumps which increases the torque being put on the 4 through bolts which in turn pulls the alloy threads in the crank cases and when everything cools down the 4 through bolts have lost some of their torque which results in the base and head gaskets leaking / blowing. A couple of years ago a friend who was I believe manufacturing alloy barrels at the time phoned telling me of the problem and suggesting that as i was olde and retired with nothing better to do I could contact my metalurgical info sources and sort it out for him.....A few hours later I did telling him which grade of steel he should use and of a Company close to him who manufactured special bolts etc and who had the correct grade of steel in stock. He had a batch manufactured and it solved the problem.... AND did so econimically.
Some people even went and hung Norton motors in frames.....If i remember correctly so doing resulted in up to 5 horse power or so being wasted due to barrel destortion which is why such frames eventually ended up with front engine supports.....wonder what happens with alloy barrels??
Nothing wrong with alloy barrels IF done correctly but they have ramifications when fitted to simply replace a big lump of cast iron.......
RAMIFICATIONS....I do so like the word!!

I called them and they are not available from British cycle supply. I have a set of Maney cylinders and they work great - 6 years so far. I use gapless rings and my leakdown test is less than 1%. Its a 73mm bore so there is very little or no distortion. I didn't even use bore plates but I would recommend them for larger bores.

Leakdown test at:

https://youtu.be/3S50Lvo9c-0

Even the original cast iron barrel has no airflow holes between the cylinders.

Or have I missed something ??

Yeah they do. I'm looking at 6 small ones between the fins and one larger oval between the lower deck and first from bottom fin.