357 Cam - 1961 Swinging Arm

[PatM20]

Bit of decision time, should I ditch the 357 cam?

I have an ally head, with standard pistons and standard carb. The 356 cam I replaced it with had lost its profile and a mate gave me a 357 cam, which I fitted some 35 years ago. The bike was then left in my barn. From memory, the 357 didn't seem to make much difference, just when you revved it on its centre stand it liked to walk along the workshop floor (which could have been caused by all sorts of things).

As I want the bike for touring will it make any difference keeping this cam or should I change it to a 356?

Regards

Pat

[orabanda]

The 357 cam delivers more power at the top end.

Compare the dyno results of three bikes with standard carbys;

Rigid A10 with 334 cam
Swinging arm A10 (cast iron head) with 356 cam
1960 SR with 357 cam.

Richard

[Servodyne]

Hello everybody. I'm a newbie so be gentle.

I've just rebuilt a Spitfire with a 357 cam in it and it's the smoothest British twin I ever had and that's with a standard crank with no dynamic balancing.
Even revving it on the mainstand doesn't produce any of the familiar walking movement. I guess I was just lucky with the state of the factory balancing?

https://www.youtube.com/watch?v=IMpF7ZD4GN8&index=1&list=LLn6l8XGJ6EyXLrc50lQzNWA

Regards

Jim

[orabanda]

Wow; very impressive!
ps; Lovely bike.

Richard

[Topdad]

yes ,very nice bike , been meaning to ask how the bloody hell you tie that fish on the back thou ??

[Black Sheep]

For normal, everyday use you are probably better with a 356. How many of us regularly take our frankly elderly A10s above 5,000 rpm? Better to stay with the better bottom end torque you get with a 356. Says me whose A10 has a 357 cam and still has torque enough to climb houses. Well, if not houses at least Hagg's Mine section at the Beamish Trophy Trial.

[PatM20]

Up Sutton Bank fully freighted is probably the steepest I will do.

[bsa-bill]

big welcome PatM20, yes I have a 367 cam. high compression stuff and alloy head, to be honest I think I was in a state of " gonna have all the stuff I couldn't afford in me yoof - mode".
And yes I also will never use the extra piff, but it was fun and rewarding to do, even allowing for the extra expense of Electronic ignition so it was possible to start the thing, and it does go well now ( never mind the starting the ET seems to have much better mapping of the timing, pinking - it just doesn't).
Have two As at present, the Flash (standard) is for sale soon as I get the front guard repainted (shame but financial needs must), then the other will get put back to a more softer tune (might keep the ET) over next winter, then I at last can get back to riding, much as I like the tinkering bit.

Now I do like your avatar, with that fish and beard just one thing missing, 

[mikeb]

i'm happy with a 356 in a 61 SR. easier on the engine and the rider. if i want to ride fast i'll take the modern with brakes to match

OTOH, maybe the 357 would sound better at idle than the 356, given part of the joy is the noise these bikes make? any views on this?

[PatM20]

Thanks for your replies.

I will probably leave the cam as is if its not doing any harm.

The fish, by the way Topdad, is an electric eel. Very handy if your dynamo packs in. You have to catch a positive earth one if your regulator is polarity sensitive.

Regards

Pat

[orabanda]

Hey Pat,
Would love to see you holding a mermaid!

[Clive54bsa]

PatM20, I have 2 A10s, 1 with the 356, my GF, and 1 with a 357, my SR. My SR motor is built to RGS specs, bigger inlet valve,  standard2 gearbox, SRM bearing mod, as 9:1 pistons and 110 octane leaded petrol etc. and goes like hell and sound great but I notice that when I get into hilly/ mountain areas, if the RPM drops below 3k, it's performance is not so good. I'm constantly shifting to 3rd and pushing it up to almost 4k so I can then get into top gear and over 3k. once it's over 3k then it pulls really hard, but let it go below 3k and try to open it up on a hill and it just bogs and with 2 up it's obviously worse. I don't have that issue with the GF, although the motor build is a lot softer, 7:1 pistons. I have decided that next time I have to split the cases on my super rocket, I'll change the cam out to a 356 as at my age I rarely take the motor over 4500 RPM. So my advice is if you want the bike to "fly" and keep the revs up, it's the 357, but for tractability go with the 356.

[muskrat]

^^^^^^^ Ditto.
Cheers

[mikeb]

Pat how do you set the timing with an electric eel? the k2f is hard enough

[PatM20]

It wriggles a bit more when the spark jumps.