My new project...

[Paul Slootheer]

I'm actually now of the opinion that the alloy a7 head is better.
Steve

Why is that Steven?

[Steven.Carter]

I'm actually now of the opinion that the alloy a7 head is better.
Steve

Why is that Steven?

We'll I realise it can only be a "feeling" but she certaily feels quicker and smoother then it was with its orginal iron head.
Here's a little story from someone who had the same feeling http://www.realclassic.co.uk/bsa-a10-su ... tuned.html

[Paul Slootheer]

Paul:
The alloy 650 heads are now quite rare/expensive, might be worth checking that no-one's put an alloy A7 head in the 'basket' - although Mr Carter seems to be running one of those on his Huntmaster very successfully!

I guess this a A10 head?

[Steven.Carter]

Certainly looks like one but you can tell by the larger valves and the dia of the cumbustion chamber.

Steve

[Paul Slootheer]

These are the dimensions...

[Simon.Gardiner]

650 bore size is....70mm?
The edge of the combustion chamber should match the cylinder bore I think, so a 66mm chamber would indicate an A7 head?
(Dunno what the sizes of the valves should be for the alloy-head twins)

SG

[Paul Slootheer]

Although it is a bit crowded in the shed, it's pleasing in it's own way...
I just love it!!

[Steven.Carter]

I've got another A7 head that I plan to prepare for future use. Certainly looks the same size

Ps. We've hearing about all the storms in your part of the world. Hope alls well

[Paul Slootheer]

Steven what is the difference between A7 an A10? Or in other words is there a difference? Do you have a A7 head as well on your Huntmaster on this moment. I'am a bit confused, should I swap it for a iron A10 head, or leave it. Also strange the stamping on my alu head which says: 56A10HC... The stamping looks genuine...

The storm did not bother us overhere, although whe are living near the coast!!

[Steven.Carter]

The A10 had larger dia. valves and the dia of the combustion chamber would be 70mm the A7 500cc head is 66mm.
Without hesitation I would use your alloy A7 head. Externally there is no difference and like I've said I think its better then the "correct" A10 alloy head. There's a huge difference in weight between an iron head compared with an alloy one also.

I'm guessing your numbers saying A10 is just coincidental. Yes I've an alloy A7 500cc head on my Huntmaster and have just looked for the casting number. Unfortunately It's unreadable.