Slant Six Tuning/Running Issues
What is the best way to go about finding this threshold?
My slanty likes lots of Idle-timing. But if you give it too much you will have problems at idle because the throttle will end up being too far closed. and the mixture too lean. So then, you will crank open the mixture screws and then it will idle just fine.
But, as soon as you open the throttle, you will get a hesitation or a bog, until the transfers come back on line. The transfers are your low-speed circuit, and the mixture screws are just the idle-trimmers. Now, still set this way, your entire low-speed circuit will be rich, because the trimmers are open too far.
And to think this all started because the timing was too far advanced.
But if the timing is too far retarded, the exact opposite will occur. Your throttle will need to be set too far open to obtain a decent idle speed. And the mixture will be rich. So then you will close the trimmers and it will idle fine. But as before when you step on the gas, the entire slow-speed system will be lean because the trimmers have been shut off.
Ok so, by this, you can know where to set the trimmers and the idle speed, and then use the timing to set the idle speed. When you do it this way, you will not have any low-speed and or driveability issues.
However, this all assumes your slow-speed circuit is actually functioning as designed. and that means you start with the correct fuel level, and that the fuel level stays correct. Next up are the Idle air bleeds at the top of the idle wells, and finally are the emulsion tubes.
Now add a bit of a vacuum leak or too tight intake valves, and things can go sour in a hurry.
In comparison, the timing is no big thing, a slanty will run on just about any timing until it is too much.
Mine likes about 8* at idle, and 28* by 2800, slowing to 32 at 3400. And easy on the V-can. And for lash, mine likes no less than .013 on the intakes and no more than .023 on the exhaust.
