I'm trying to tune the idle air mixture on my eddy 750 and am going off of the vacuum method. I turn the screws CW or CCW until highest vacuum is achieved. It doesn't appear that the engine changes much, maybe 2 lbs in either direction. My highest vacuum reading is 16.

Is this a good reading for a stock built 440 with a 268/454 cam?

Should I be seeing more than just a 2 lb drop with adjusting the screws either full in or full out? I don't hear too much of a chane in the RPM. For tuning purposes I've cranked the RPM to 850.

Thanks

Yes. 16lbs is decent. I don't even get 11lbs on my 360...Now here is the catch, timing at idle has a lot more to do with how strong your idle is, than any vacuum reading. Not enough, and its way too low, too much and its a pain to fire it, but the idle is strong. Too many Mopar distributers have too big of a spread between idle and total.

Most people set total timing, and your usually stuck with whatever you get for initial timing at an idle, but sometimes that isn't good enough. If not, I can give you some pointers, but since you have a good vacuum reading, it seems you have enough timing at idle and it isn't very sensative to the mixture screw adjustment, this is good, but now you really need an A/F gauge to see where the carb is at as long as you have an rpm your happy with.

If not, you may need to close down the throttle blades a little if your idle is too high, and re-adjust timing a little.

1st slow your in gear idle speed down to where you are back on the idle circuit so the screws will have an effect. find the "lean drop" adjusting procedure

I start by adjusting the timeing with the vac gauge to see where the engine likes it at going by the highest vac reading. put a light on it to see where it is and make a note of it for referance later..then adjust from there up or down.

then i do the airscrews to fine tune the highest vac reading from there.

then test drive to see if it pings at WOT,back off as needed to stop any ping on the WOT blast,some times it will have a very slight ping when its on the jagged edge of the timeing curve.

recurving the stock dist is always a good thing to dial it in.

I shoot for the rpm drop going into drive to only change about 100 or so rpm. when you do the airescrews it will show a change that you cant hear most times.

i run a low idle on mine at about 650-700 rpm

thats the way I do it on my junk and works fer me

Thanks Guys! Looks like I've got some great advise to try out !