4 replies to this topic

[Magna-Flash]

I´ve googled all day - but haven´t found this...

 

I´m trying to find a suitable dizzy (to start with) for my MG1100 engine that I will put in my Mini.

What I´ve been looking for is:

 

*When does maximum advance start, at what RPM - and what is it? 30 degrees? 32?

*What is the dynamic timing figure? (RPM+degrees)

*A complete curve would be jackpot

 

I just want to know where to start - cause I read somewhere that the 1100´s was special, dizzy-wise:

 

Unlike the 998, the 1100 is a little fussier on the ignition advance curve side of things / Keith Calver

 

Large-bore engines are less fussy about exacting ignition requirements than small-bores. The 1100-type being the most difficult to get right, with very particular requirements mid-range when tuned and worlds apart from large-bore curves. This should be remembered when swapping distributors from one engine to another. An 1100 dizzy in a 1275 will at run OK, but a 1275 in an 1100 can be courting disaster /Keith Calver

 

 

[carbon]

According to the BMC factory manual for 1100/1300 the static advance was 5 degrees.

 

Mechanical advance starts at 700rpm, about +21 deg by 2,800 rpm and max +30deg by 5,000rpm

 

Serial numbers 40853 or 41028 were standard fit. Vac advance was 14 deg at 7 inHg.

[Magna-Flash]

Thanx

[Magna-Flash]

Found a pdf on the fabulous web with a bunch of different dizzys. However I´m a bit confused how to read it - the advance values for specific rpm´s doesn´t seem logical.

Can someone please explain how the values Carbon submitted so greatly differ from these:

[jaydee]

Remember todays fuels need different advance so use the factory specs as a rough guideline, then have it rolling roaded by someone that can recurve your dizzy (ie ML motorsport, slark etc..)

The 1100 engine being long stroke needs more advance than its 998 brother.

Probably the table above comes from measurement of the mech advance of the dizzy, meaning that if you static time the dizzy at 5 degs you have 6.5° at 450 rpm, 18° at 1850 rpm and 22° at 3200 rpm. àsounds like a typical ingition curve for an MG engine.

I'd look for 30 degs at 3500 rpm for max power, so try setting static timing around 6-8 degs and carefully listen for any pinking under load and holding back/juddering under deceleration at any sing advance back (retard) a couple degrees.

I'd have it recurve by an expert anyway.