Author Topic: Tired old 1955 A10 Golden Flash needs a boost!!  (Read 2487 times)

Offline magicflem

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Would anyone have information on the following:
I wish to upgrade my bog std 1955 BSA A10 G/Flash engine.
I have a Super Rocket Big Valve alloy head and want to know if this will fit existing cylinder and also what is the best HC piston and cam to use. Basicaly want I want is to beef up the old girl with a bit more bottom and top end performance.
Any info would be greatly appreciated.
1930 BSA B30-3 Side Valve Girder (being restored)
1955 BSA A10 Road Rocket
1955 BSA A10 Golden Flash
1956 BSA A10 Road Rocket
1951 BSA A10 Golden Flash
1956 BSA DB32 Gold Star Clubman
1958 BSA A10 Super Rocket
1961 BSA C15 (being restored)
1961 BSA C15 Star "America" (being restored)
1961 BSA A10 "Big Valve" Super Rocket (being restored)
1963 BSA A10 Rocket Gold Star

Offline Beezageezauk

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Re: Tired old 1955 A10 Golden Flash needs a boost!!
« Reply #1 on: 09.11. 2010 09:44 »
Be careful with this one.

Are you using thin flange barrels on your motor? 

BSA changed to thick flange barrels in about 1960 after they found the sports models with high compression pistons and high lift cams caused the thin flanges to crack and eventually break away from the barrel.  I'm sure that you wouldn't want this to happen to your engine!!

The thick flange barrels were even used as standard on GF's in 1960 when they were fitted with the semi high lift camshaft (356) and low compression pistons.

Beezageezauk.


Offline magicflem

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Re: Tired old 1955 A10 Golden Flash needs a boost!!
« Reply #2 on: 09.11. 2010 09:48 »
The flange is approx 13mm. Is this thick or thin?
1930 BSA B30-3 Side Valve Girder (being restored)
1955 BSA A10 Road Rocket
1955 BSA A10 Golden Flash
1956 BSA A10 Road Rocket
1951 BSA A10 Golden Flash
1956 BSA DB32 Gold Star Clubman
1958 BSA A10 Super Rocket
1961 BSA C15 (being restored)
1961 BSA C15 Star "America" (being restored)
1961 BSA A10 "Big Valve" Super Rocket (being restored)
1963 BSA A10 Rocket Gold Star

Offline MG

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Re: Tired old 1955 A10 Golden Flash needs a boost!!
« Reply #3 on: 09.11. 2010 10:00 »
The thin flange was 3/8inch and the thick flange 1/2inch, so yours should be thick flange barrels.

The Rocket alloy head will fit on the barrels without any problems, but you might have to grind a bit of material away in the rockerbox to clear the top valve spring collars. And you'll need new alloy head bolts of course!

I can highly recommend the forged Wiseco pistons (9:1) from Cake Street Classics. They cost quite a bit more than the usual stuff, but they are well worth the money.
I've posted a pic of mine here:
http://www.a7a10.net/forum/index.php/topic,3195.0.html

Ref the cam: If you are after top end power at high revs, the 67-357 Spitfire profile is the way to go. For bottom end torque, I'd recommend a 67-356.

Cheers, Markus


1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

www.histo-tech.at - Restoration, Repairs, Racing

Austria

Offline Beezageezauk

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Re: Tired old 1955 A10 Golden Flash needs a boost!!
« Reply #4 on: 09.11. 2010 10:18 »
I guess they're thick flanges so you're on a winner.

FYI, the '60 GF's were fitted with 356 cams and 7.25:1 pistons.

For road use I would go for this, or maybe raise the compression slightly higher.  If you wanted higher cruising speed rather than brisk acceleration you could also fit a slightly higher than standard engine sprocket engine.

Personally I think the 357 cam would be too potent, as would be really high compression pistons as you also need to think about metal fatigue!!  These motors aint as young as they used to be and can fail big style if too much is asked of them.

Beezageezauk.


Offline magicflem

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Re: Tired old 1955 A10 Golden Flash needs a boost!!
« Reply #5 on: 09.11. 2010 10:28 »
Thanks guys, the advice is ver helpful.....any other advice would be greatly appreciated.
1930 BSA B30-3 Side Valve Girder (being restored)
1955 BSA A10 Road Rocket
1955 BSA A10 Golden Flash
1956 BSA A10 Road Rocket
1951 BSA A10 Golden Flash
1956 BSA DB32 Gold Star Clubman
1958 BSA A10 Super Rocket
1961 BSA C15 (being restored)
1961 BSA C15 Star "America" (being restored)
1961 BSA A10 "Big Valve" Super Rocket (being restored)
1963 BSA A10 Rocket Gold Star

Online bsa-bill

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Re: Tired old 1955 A10 Golden Flash needs a boost!!
« Reply #6 on: 09.11. 2010 10:48 »
You will loose tractability as you increase the compression ratio but gain overall power

High compression - jump canyons
Low compression - climb walls

I am in the (long) process of doing what you want to do, I have a 357 cam and 9.1 pistons but will keep these until the engine is a good bit free'r than it is now after rebore.
So presently on 356 cam and 8.5 compression pistons, have opt'd for a slight gear reduction (very slight) to compensate for loss of tractability

Head should be no problem as MG says remember to get the proper washers for under the head bolts, and you will need longer studs into the rocker box as well as two sleeve nuts for the rear of the rocker box plus the sleeve nuts also have special washers.

Check what size carb you have at present, you might get away with the bore size if it's not to different but slide and main jet will possible need changed

Good luck with it
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco