I recently bought a vehical fitted with a standard MG Metro engine. It ran well enough but when I checked the timing it was 25+ degrees advanced.I took it back to the book recommended 16 degrees and now it does not pull as well as it did.The distributer is a new electronic from Minisport and if,at tick-over, I slowly turn it to advance the timing the revs pick up considerably. I suppose I need a rolling road. I am running on 99 octane with a leadtetraethyl additve.
Mg Metro Timing
Posted 22 March 2020 - 06:10 PM
When checking the timing, are you doing it with the Vacuum Advance disconnected and at the correct engine RPMs?
Posted 22 March 2020 - 09:08 PM
Posted 22 March 2020 - 09:56 PM
I guess I'm 'old school', but back before we had rolling roads and electronic timing lights we used to set the timing by starting with a 'nominal' figure at which the engine would run. Then we set the tickover to around 1000 rpm and advanced the dizzy until after the revs increased by moving the dizzy, the revs peaked and started to drop. Then the idea was to retard it to just before the position of max revs. Nip up the bolt so that the dizzy would move by hand, but not too tight. The car was then driven gently to get it fully warmed and it was then driven, ideally up a slight incline, in 3rd or top gear at around 3500 to 4000 rpm. Full throttle was applied and if the engine could be heard to 'pink' under this load the dizzy was retarded a couple of degrees until the test showed no 'pinking'. Then repeat at different revs from around 2500 rpm up to 5000 rpm and make sure that there is no 'pinking'.
That is as near to the optimum ignition setting as you can get.
The only problem is that with modified engines it can be hard to get enough mechanical advance and at optimum advance it can be difficult to start the engine when it is hot. This shows the need for a different dizzy curve.
Posted 23 March 2020 - 08:24 AM
Posted 24 March 2020 - 10:11 PM
Do Minisport say that's the dizzy for an MG Metro engine ?
This is why I and many others use programmable ignition. If the engine likes lots of idle advance then that's what you give it. It's perfectly normal for an engine with a performance cam to want alot of advance for a good idle.
And the other advantage of programmable is, next time you alter the engine spec, you just set the optimum again, for free ! So the initial cost of the programmable ignition is re cooped in the long run
Edited by Pigeonto, 24 March 2020 - 10:17 PM.
Posted 25 March 2020 - 12:29 AM
I am not allowed programmable of electronic ignition on my historic rally Cooper 'S'.
When \I built my engine I set the CR to 11.1:1 with an Aldon 'Red' dizzy. It was set up by Peter Baldwin on his RR and was very good, pulling max power at 6400 rpm with the 286 cam, However, it was difficult to start when really hot and on 0ne rally I had to retard it a few degrees.
After speaking with Aldon, they built me a new dizzy with a different advance curve and with more mechanical advance. They told me what to set it to and it has since been fantastic. I think they gave me about 4 degrees more mechanical advance and slowed the advance a bit, but I'm not sure of this.
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