Morris Minor Owners Club

I have a 1275 Marina engine fully reconditioned, and wish to up the horsepower.
I am told a different camshaft would achieve this but that it would also tick over
lumpy. Is there anything I can do to gain more horsepower without my car ticking
over like a building site dump-truck? I would sooner leave it like it is than have my
lovely car tick over lumpy.

Try the Kent Megadyne 266 - a bit more zip and smooth idle!

Or a swiftune SW5

I had a kent 276 in a marina engine and it idled okay

Maybe change the head and exhaust etc

The old SW5 has long been 'found out' - see Adrian Dodd for what are now considered by the Mini lads to be the best cams for the A series. You do realise it's a big job to change the cam on a 1275 engine ?? There's no need for rough idling - also note that there is no point in fitting a cam that peaks at anything much over 6000 rpm unless you are rebuilding the engine with balanced / strengthened components -and do you intend to rev it like that anyway??