I am running a freshly rebuilt series 2 DHC - rebuilt engine and carbs etc etc.
The car has open trumpets as the air box has been removed.
It runs perfectly at low speeds but is too lean on acceleration and at speed.
I am running UM needles and was thinking these are part of the problem. My thoughts are moving to UE or UB (UO probably too rich) - but wondered if anyone had a view.
Also running a 123 distributor- compression and valve timing as well as ignition timing all perfect.
General running also perfect.
Any help appreciated.
Paul - re the lean running at speed - gentle acceleration was causing a hesitant “flutter” and the car felt very underpowered. Hard acceleration resulted in backfire through the carbs. I have kept the UM needle set up but richened the mixture - now reading 13 in CO2 previously 6. I also had cooler plugs (NGK 6ES) which I have changed to standard 5ES hotter plugs to avoid fouling with the richer mixture. The result seems very positive. Good running - good acceleration now - although conscious that it is not very rich co oared to before.
I promised to revert with the ignition curve setting in my 123.
It was set up on curve 2.
However only a couple of weeks in and the 123 seems to be failing! Misfires under load despite the set up being as per set up instructions.
Swapped it back for a standard dizzi and all is well! Will check again thoroughly when I have more time - and check the coil (although I have a new one) but at the moment the car runs fine on a standard Powerspark £70 dizzi and performs poorly with a 123.
The new 123 dizzi WAS at fault, in fact when examined by engineer we noticed various burn and arc marks on the inside of the 123 dizzi cap.
Car now running like a dream on a new Powerspark dizzi, Coil and leads - OE needles and NGK 5ES plugs. These have been in for around 300 miles now - lovely colour no fouling - completely opposite to the situation under the 123 Dizzi.
May be that I was unlucky but I certainly won’t be using 123 dizzi again. Very expensive - failed within a couple of weeks and when it WAS working it didn’t change anything over my standard dizzi - certainly no better.
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