I need to buy some cable to connect battery to starter motor on my focus st170 engined build. Problem is I don't know what amp cable is required. They seem to range from 110 amp to 485 amp. The length of the cables will less than 1.5m.

I bought some ready made one's from Halfords, don't think they were too expensive.

Not sure how much help it is, but I used 300 Amp for my Rover V8.
Works fine.

CBS do 345 amp 50mm2 cable, that should do the trick then.

I would say that 25mm would be more than adequate. Try VWP http://www.vehicle-wiring-products.eu/product.php/579/battery-starter-cable

Yep, I went with 300 amp (40mm2) to be on the safe side for a V8.

You can probably go down in rating from there for a 4 cylinder.

Paul

If I go with 40mm2 then I should be safe. I'd rather stay on the safe side.

I think you could probably go with 25mm2, but 40mm2 will definately be ok.

Speaker wire should be ok. The stuff from wilkinsons....

Quick update. I measured the standard focus starter cables today and the core was approx 6mm diameter which would mean about 28mm2.

I guess I'll go with 35mm2 cable then instead of 40mm2 and I'll be well safe still.