A7SS Head Gasket - Part Number

[Terryb]

I need some guidance please, for my 1955 A7SS:-

Head gasket - Looking at the parts book 1954-57 edition for 500cc and 650cc bikes, the part number for 'A' Group (Plunger and Swinging Arm Frames) is 67-255. I can not find any other numbers for a 1955 A7SS, so am I to assume that this gasket fits both A7's and A10's?

Terryb

[Slippery Sam]

Hi Terry, merry Christmas.
I'm not an expert but couldn't stop myself doing a quick number check and rather then use the parts book I had a look on Daganfly.  They list the 67-255 as A10 1950 through 62 and for the A7SS 50 to 62 they list a differnt one  67-382.
I'm wondering if there is a difference in the bore size?  I have an A7SS alloy head and know it needs the combustion chamber opened up a little to fit the A10 70+mm bore.
I think on this occasion you are right to query it and seek clarification from one of the many experts on here.
Raymond.

[Terryb]

Raymond, merry Christmas to you,

You are right there is a bore difference A7 = 66mm and A10 = 70mm, but the 67-382 is for Shooting Star 1956/57 and the 67-255 is also listed for a Road Rocket of the same year according to the same BSA Parts Book. Looking at the two Heads the most obvious difference is that the 56/57 has a cast integrated inlet manifold and mine is separate.

Terryb

[muskrat]

G'day Terry.
67-382 is correct for A7, A7ST and SS.
If your asking for your 1106 head it's 67-255.
So to clarify you have a 54-55 A7SS with a 54-55 A10RR head ?
Cheers

[Terryb]

All,

I've manage to do a swap with a colleague my 1106 for an A7 Head part number 1102 and I've found a link for an A7 head gasket on eBay.

So many thanks guy's and happy New Year to you all

Terryb