mk1-forum.net

What’s the general consensus these days for all-in ignition advance on modern E10 fuel for a standard-ish 1275+ S engine?

Assume a 9.75:1 CR with a fast road cam such as MS Evo1, I’m thinking maybe 32° at 4k RPM ?

I do it by ear.

Start off at the book figure.

Advance until you hearing pinking on heavy acceleration, and then retard by a degree.

Or get it done on a rolling road.

With so many variables, its difficult nominate an absolute figure.

(What is all-in ignition ?)

All-in = total advance (base + mechanical)

If I'm not mistaken the factory distributor for the 1275S comes with 30 degrees mechanical advance built in (15 stamped inside). The book spec for them is 4 degrees at idle and 27-31 degrees at 7000 (1966 BMC workshop manual). I don't know how you get 31 at 7000 with 30 built in if you start at 4.

I run 10 degrees at 1000 on 95 octane with 10.1 CR in a 1310S. SW8 cam. No sign of pinking. Then again, I have yet to test whether my old dizzy is actually advancing as it should.

Hi iain

30 to 32 degrees is pretty reasonable. It may pay to see what rpm the timing tops out at. ( Some dizzys keep going after 4 000 - not that i think this ideal on our current fuel)

Thanks all.

Just re-discovered the printout with the curve for my particular S distributor. It shows max 14 degrees camshaft advance at 3500 rpm [i.e. 28° crank], so I’ll start at 4 degree static and see how it goes...