eightTfourTA

iTrader: (3)

I'm trying to adjust this bastage air bleed screw to the dwell meter. For some reason, I can't get it down to 25-35 degrees on the 6 cyl scale. It will go to about 35-40 and then won't respond to any more changes. I've got the rich stop at 3 turns down from top, and the lean 5 turns up from bottom. Idle mix screws are about 4 turns out. I'm also getting a slight off-idle bog, but only sometimes, if it makes any difference.
Is there something wrong, or is the adjustment close enough that I shouldn't have to worry about it? And, would this off-idle bog be related if something is indeed wrong?

Damon

The idle mixture screw adjustment will affect your IAB setting drastically. Try turning the mixture screws in 1/2 turn and then go at the IAB again with the dwell meter hooked up. See if you're getting closer to the desired dwell. If it gets worse, open up the mixture screws and try again. Once you have the hang of it it's easy.

eightTfourTA

iTrader: (3)

You da man Damon, thanks!! The bog went away too

five7kid

iTrader: (14)

Just curious, which way did you have to turn the idle mixture screw?

eightTfourTA

iTrader: (3)

I had to turn it clockwise. Bringing them out only seemed to make things worse. After I got it set I turned them both in and counted the turns then set them back, they're about 3-3/4 of the way out.

five7kid

iTrader: (14)

That makes sense. Since the "dwell" relates to how long the solenoid is energized, and energizing seats the mixture valve; being energized more than spec indicates the idle mixture is already too rich. Not sure how that relates to a bog, though.

I fiddled with the IAB adjustment a long time ago, didn't touch the mixture screws. Same condition, also always seemed to idle a little rich, but I don't have an off-idle bog problem.

Now I'll need to go and play with mine again...

Damon

Glad to help.

A mere 1/4 turn difference seems like not enough to make much difference, but obviously it helped. I try to get mine so that the IAB is in about the middle of it's range (about the middle of the screw thread range on the top of the carb) when the dwell is dead-on where I want it. In short, I put the IAB in the middle of it's threads and then adjust the idle mixture screws until the dwell comes in where I want it.

This is all totally unnecessary if it's good enough to make you happy, but I thought I'd share an alternate way of doing it. This is the way I prefer to do it if you have already taken off the idle mixture screw caps and have easy access to their adjustment.

eightTfourTA

iTrader: (3)

Actually Damon, that's kinda how I got it back into adjustment. Being told to adjust the idle mixture was all I needed to get me started, and once I started futzing with it, it all became clear somehow-weird how that happens.
But anyway, since I was unsure of how many turns those screws were already at, I ran the engine and turned them both in until it almost stalled. Then I started watching the dwellmeter along with my vacuum gauge as I turned them out 1/2 turn at a time, and tweaking the IAB every now and then to keep it within the range. Got it idling at 19Hg of vac, with the dwell right in the 30-35 range. My a/f gauge also helped me a little bit, since before it was nearly pegged out rich on the idle, and now it stays right in between lean and 14.7. Gets a little leaner under load, which seems right, too. The cool thing is, it hasn't hesitated or bogged off the idle like it used to. Just lights the tires now Thanks again!