8 replies to this topic

[AGRO_RB]

Car - Morris Mini Clubman
Year - 1973
Engine - 998cc

So, now that I've got my fuelling pretty much spot-on (going off plug colour and lifting the dashpot piston, colourtunes are worth drug money over here ), I need to set my ignition timing properly. Car drives nicely, it's just a little flat at full throttle and up in the revs. I've tried searching for guides on how to do this however none give any clear answers. I upgraded to a Powerspark electronic ignition which came in a new 25D distributor, as well as a genuine Lucas gold sport coil and new 8mm Lucas leads. Obviously initial timing was fine but I've not been able to get rid of the flat spot which is a shame as the cars drivability has improved so much. I own a working timing light which helps, by the way. I've noticed people say to advance the dizzy as far as possible and load the engine up until it pings, then back it off until.the pinging stops, however as I have a fairly decent exhaust leak I can't hear the engine itself over the leak Also, where are the timing marks on the flywheel, all I can see is the clutch!

[Earwax]

Hi , there is an inspection cover on the clutch cover (wok) undo one screw and swivel it open. you then use a mirror to spot the timing marks   but before doing this just check that the crank pulley doesn't have timing marks ( don't need mirror)

[lrostoke]

Probably worth sorting the exhaust first, will have an effect on how she runs.

 

Does the dash pot on the carb have oil in

 

Another possibility is that the dizzy is curved wrong for your engine.

 

If you do find the timing marks and you have a timing gun with advance function, up the revs to 4000 rpm, set the timing to 30 - 32 degrees , drop the revs back down.

See how that does you

Edited by lrostoke, 20 December 2013 - 07:24 AM.

[AGRO_RB]

Yeah, the pipe has split just at the base of the manifold so the motor is essentially breathing its own crap...

When you say it's curved wrong, do you mean that the advance curve doesn't match the rpm range of the engine? Is there a way to test and remedy this? I REALLY don't want to go back to points

Yes I topped the dashpot up myself as it was empty 20W50 as it's all I had, too heavy? Remember it's summer here!

Will inspect the crank pulley when I get back in January, I pulled the inspection cover off the clutch cover, so as recommended I'll have a look with an inspection mirror in the new year :)

Cheers for the help, as always

[lrostoke]

If you still have the points dizzy.

 

Then you could write down what the curve is on that.

 

start at 1000 rpm, check what timing reading you get, up it in 500 rpm increments and take readings.

 

then fit the new dizzy and do the same

[jaydee]

Plot your ignition curve as lroke said. Will help us to understand if theres something wrong on the ignition side.

20w50 can be a bit thick resulting in a slow what acceleration. 

Did you check the spark plug colour at idle of under load, theres a huge difference between them..you can have plugs of a nice grey at idle then have a weak mixture at full power..you can have clean plugs but you're actually running rich..

[daenesh]

aren't grey plugs a bit too lean?

[jaydee]

Modern fuel give different colour, if plugs are of a tan colour you're on the rich side, in most cases too rich

[dklawson]

When you say it's curved wrong, do you mean that the advance curve doesn't match the rpm range of the engine? Is there a way to test and remedy this? I REALLY don't want to go back to points

 

There have been hundreds of different advance curves for A- and B-series engines.  Even when the engine and distributors were new and fresh from the factory those curves were a compromise selected to provide adequate performance with the fuels available at the time.  Decades later a vendor is supplying you a "one size fits all" product for A- AND B-series engines so it too must be a compromise.  In short, yes... the curve of your new distributor may not be right for the build of your engine. 

 

You said you have a timing light.  Is it a fixed timing light or a "dial back" light with an advance knob?  Dial back lights are much easier to use when setting the  max advance as Steve suggested above.  If you have a fixed light it is still possible, just let us know what you have and we can advise you.

 

Once you have fixed the exhaust leak you really should be able to hear if there are any bad engine sounds from setting the max advance.  Usually the problem is obvious as you will hear "marbles in a tin can" when you accelerate under high load.  Once you have the max advance set, continuing flat spot problems MAY be addressed by carb needle changes.  However, you MUST sort out the ignition first.  Always save fuel adjustments for last.