What is it?

[worntorn]

Engine number seems to indicate 1956 swing arm Gold Flash, but why the HC below?
Would the frame be from 1961?

[Topdad]

Doesn't CA indicate small journal and HC ,high compression with sport cam , I'll await being told what they really stand for.

[BritTwit]

My understanding of the designation is as follows:

HC      High Compression
HHC    High Lift Cam + High Compression 

[bikerbob]

That frame number would indicate that it is a 1954 either A7 or A10 swinging arm frame. 1954 began CA7 -101 whilst 1955 began CA7 7001

[chaterlea25]

Hi
Have a look here
https://www.britbike.com/bsapitstop/dating/1951-60.html

John

[worntorn]

I'm thinking now that it would be a 1955 frame since 54 and 55 were the only years for a CA7 prefix and this is 13,356, very near changeover to the next frame prefix, FA7. BSA started the CA7 frames at 101in 1954 and were at 7001 by the  a beginning of 55, so 7000 frames per year puts 13,356 as a very late 55.
It appears  new models start at engine and frame 101 as a rule .
The engine appears to be a 1956 Gold Flash, but why would a Gold Flash be designated HC  or high compression? Wasn't high compression limited to the sports models, the RR and SR etc ?
Did the 56 swing arm Gold Flash have an alloy head?
This engine has an alloy head, but it might not be original

Glen

[trevinoz]

Glen. '56 & '57 frames were EA7.
Regarding the "HC", remember that the standard compression ratio was 6.5:1 and if higher compression pistons were fitted, I think usually 7.25:1, the case was stamped "HC".
It is not uncommon on Flash cases, I have a set of BA7 cases so stamped and have seen others.

[chaterlea25]

Hi Glen,
Does the engine fitted have a thick flange cylinder?
It is not unusual after all the years for engines to be rebuilt using cases cylinders and heads etc from different years
and models
It would be interesting to know whats inside the engine now? big or small journal crank, cam type etc
A boroscope inspection would show what pistons are fitted

John

[Clive54bsa]

They made Road Rockets in '54

[JulianS]

The engine was probably made for the export market and fitted with higher comp pistons to suit that market.

The first Road Rockets came out in April 1954 and was export only until 1956 season. The bulk went to either Hap Alzina on West Coast USA or Rich Childs later BSA Incorporated on East Coast.

The thick flange barrels arrived in 1957 on the Road Rocket.

[RichardL]

Jeez, Julian, were you at the Small Heath auction where they sold the file cabinets?

Richar L.

[worntorn]

The engine has thin flange cylinders.
Thanks for the replies, now I know it is a 56 
Gold Flash engine, high compression ( but not very high) and a 55 twin frame.
My friend is hoping to buy this bike and asked if I would post the question.

Glen

Btw,  wouldn't the engine above , CA10  755
be a 54 Gold Flash ? I believe the Road Rocket would be CA10R.

[JulianS]

Agree CA10 755 is a Golden Flash motor, probably exported given the HC.

Road Rockets are found with prefix CA10R and CA10RR.

[BritTwit]

Agree CA10 755 is a Golden Flash motor, probably exported given the HC.

Road Rockets are found with prefix CA10R and CA10RR.

I've had both.  Never figured out what the extra "R" meant.