Post by Simon1275mpi on Apr 10, 2010 10:27:25 GMT
1. why did you not put a duplex sprocket and chain on. they dont stretch as quick
By my advice
Unless you invest in a vernier adjustment or get someone to setup a duplex with the correct 'woodruff'? keys, the investment is misplaced as you may not of resolved far greater issues of ignition timing scattering.
So why not first resolve the greatest variable for the ignition inaccuracies? The distributor! A rebuilt dizzy set with the correct advance curve setup with a strobe light will bring the timing issues from +/-20degrees to then +/-5 degrees inaccuracy. Ok, then it would be worth spending the money on a duplex, and then getting it setup correctly with a vernier. But how deep are your pockets.
Why a rebuilt dizzy? All dizzys have an advance curve, so as the engine sucks more air in, via the Vac pipe it sucks the dizzy and the spark is delivered earlier to burn the fuel intime before the piston reaches the top of the compession cycle. The VAc advance is just a simple sprung arrangement, by the spring looses its bounce or vac thing leaks, throwing the whole timing out. Plus the bearings on the dizzy spindle wear so it wobbles, even more inaccuracies.
The best standard value dizzy out there is a late mini/metro 45D distributor, second hand off ebay £30. Oh and thats electronic ignition now! Just two wires go to the coil + and -, simples. And a lot of these dizzy's are in peoples sheds/spares pile... So lose those clockwork points which need regular setting up. By compassion a standard duplex chain setup is £30 or £70 for a adjustable one...
Value for money spent of the correct items I say!
PS, see AC Dodd and ML motorsport for the item.
PSS dont just buy a dizzy off the shelf, explain your car, engine and use to ensure the correct setup!