Hi, I’m hoping you can help me. I am an ex member of the club and I am now restoring a mk1 Sprite. The car runs on unleaded and has not been modified to accept this fuel. It has an inline additive system.
It runs very rich and I have been told that in order to cure this problem I have to alter the timing to allow for the lower octane fuel. I have been told that I should advance the timing to compensate, but also that I should retard the timing to sort this problem.
Can you confirm which I should do and how many degrees (advance or retard) in relation to top dead centre.
Regards.
1. I think I know what you mean by inline additive system – they don’t work, you’ve been conned.
2. if the mixture is too rich then you need to adjust the carbs; ignition timing does not affect the fuel/air ratio.
3. not knowing what the ignition timing is currently set to, it’s impossible to know whether it needs advancing or retarding (or leaving well alone)
JOIN THE CLUB ! fuel richness is controlled by the needles in the carbs , check that they are the same and as per the book. there is an adjusting nut under the carb to set the height . CHECK FIRST THAT THE CAM or CABLE for the CHOKE ISN’T IN FULL TIME OPERATION !
also the oil in the carb dashpot can have an influence however this usually presents itself as a weakening of the mixture during acceleration phenomenon.
as for timing worn distributers can affect the timing , Best method is to get the fuel mixture correct first ( BL or Haynes or any decent manual) Aim for about 1000 rpm on tick over by stting the carbs . Start the engine , let it warm up . choke in , with the clamp on the distributer loosened rotate the distributer body a bit in both directions to get the optimum tickover without it being lumpy . or smoky. adjust the carb (accelerator cable cable ) to get the tickover correct . the choke should just be on the start of the cam – any further higher on the cam means you will be running with the choke on all the time i.e. rich . Aside – l sometimes use the choke to cool the cyl head if I have been thrashing the motor and it is on the verge of overheating , not for too long tho , don’t want to wash the oil from the bores.