All-in ignition timing

[iain1967s]

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 ?

[woodypup59]

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 ?)

[timmy201]

All-in = total advance (base + mechanical)

[abri]

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.

[Earwax]

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)

[iain1967s]

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...