[Healeys] air/fuel mixture

Oudesluys coudesluijs at chello.nl
Sun Jun 21 03:33:33 MDT 2009


Jess,

Before you can tune the carbs you have to adjust the valve clearances 
and the timing to be spot on. A check on the compression cannot do any 
harm either. Failing this makes the adjusting of the carbs senseless. 
Take off the air filters.

Balance the carbs using a length of tubing to adjust untill the hiss 
from every carb is the same (old fashioned way) or use carb balancers.
Then adjust the mixture using the Colortunes (one per carb is very 
convenient). You may have to do this several times as the balance tube 
causes interference between the carbs.
If you use the Colortunes, start setting the carbs rich and lean out 
untill the orange just disappears, then stop. It should be at around 4% 
CO at that moment.

If the color from the Colortunes at present is orange it means 
incomplete combustion caused by:
over rich mixture
out of tune ignition
incorrect valve timing or clearances
a combination of these.

Heavy oil consumption causes a purple/reddish color which can sometimes 
be mistaken for rich running.

Running hot can be caused by:
lean mixture
incorrect ignition timing
blown head gasket
eroded waterpump
scale in engine/radiator, not uncommon in US cars as often water instead 
of coolant has been used.

Having the radiator cleaned is a dicy bussiness. Often only the visible 
channels are rodded. You have to take top and bottom tank of to be able 
to do a proper job. Best is to have the core renewed, which will not be 
very much more expensive than a proper cleaning/rodding job.
Treating with caustic soda or one of the available radiator cleaners is 
not realy very effective.

Kees Oudesluijs
NL


Jess Power schreef:
>  I need some help-----again.I bought a colortune and synched the carbs 
> in my BN1.It is running really rough and the colortune shows yellow or 
> a too rich mixture even with the air/fuel mixture nuts almost 
> completely closed.It is still running hot even with a new water 
> pump,new thermostat an a radiater rodding.I think the timing might be 
> off.It is backfiring from the tailpipe and the carbs.Any suggestions?
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