Ideal Timing?

[natertot]

Hello,
Failing emissions on carbon monoxide, investigating ignition timing. I set my base timing, but the curve seems strange. Is this typical? What should I be aiming for? P.O. had put a very new looking distributor in, bright blue. Advance is controlled by computer (TFI).

BASE (SPOUT disconnected): 10* total @ 800RPM
AT IDLE (SPOUT connected): 23.5* total @ 900RPM
ALL-IN (SPOUT connected): 41* total @ 1700RPM

Seems like it goes all-in fairly early, and the large jump in advance from base timing to idle is surprising as well.

 

[franklin2]

You have no control over it except the base setting. What you are seeing is normal. The more advanced the timing is, the more efficient the engine is. It will keep it as advanced as it can for all conditions. No load conditions will have it advanced a lot.

If you have a knock sensor and the engine is fully warmed up and in cruise mode, the computer will advance the timing even farther till it gets a signal from the knock sensor, and then it will retard the timing and then start advancing it again, till it gets a knock signal again. It does this continually. This is how it controls the timing and compensates for different fuel quality and octane rating.

 

[Uncle Gump]

Carbon monoxide is related to a rich fuel mixture.

A timing issue would have high hydro carbons.

I think you need to figure out why your too rich.

 

[gaz]

@natertot
Since you know that your getting at least enough fuel, perhaps consider the stregnth of your ignition system; if you haven't conducted a recent tune-up, new plugs/wires can change the world. If you have then perhaps your coil is providing a weak/intermittent weak spark; I have seen this more than once.

If your fuel and ignition are "not improvible", then perhaps consider advancing your base timing; +12° is suggested even in our TECH pages. There is also the method I was taught on Bowtie 350's, where, while at normal operational temperature, shut it down, disconnect the spout. Start it up and advance the distributor using a vacuum gauge as your guide. As it is advanced, vacuum will climb, climb, climb to a point where (if a needle gauge) then flutter, after the flutter, any more advance will lower the vacuum. Retard it to below the fluttering point, then advance again to just as it starts to flutter...back it off a hair, shut it down, tighten the distributor and plug in the spout.

As mentioned by others, the timing with the spout in is not adjustable with the spout plugged in. This should result in optimum timing and is how I passed Cali4nia emissions, while stationed there.