Poor idle after timing adjustment on 440 BB

REMMY123

MEMBER
1974 DODGE DART
74,000 MILES

I decided to adjust the timing on my 440 because it was bogging down at initial acceleration, I had recently rebuilt the 850 CFM Street demon Carburetor And no matter how I have the carb adjusted I cannot get rid of the hesitation when I initially hit the throttle, if I advance the throttle from the idle speed of 850 RPM there is a dead spot from 850 all away to 1100 where the carb just sucks air and wants to stall out, I believe that the accelerator Pumps are working fine as at 1500 RPM the squirters are working properly. So I decided to check the timing which I have not done since I bought the vehicle a month ago, the timing was way off, I advanced it to 13° initial and after running some checks reassembled everything jumped in the car drove it and it ran great having Eliminated almost all The hesitation it had before. It's from that point that things got weird, I did that work in the morning and when I came back in the evening to start and drive it it ran completely different than it did in the morning barely idling out of the driveway. I checked all my spark plugs and wires and their connections and everything seems to be fine there. I even manually found top dead center on the number one cylinder And the line on the harmonic balancer perfectly lined up with the zero mark on the block indicator, I then checked to make sure that the rotor inside of the distributor cap was pointed at the number one plug wire and it was. Since it's been running bad I have readjusted the timing with no success on making it idle better and adjusted the carb in every way I know how and I still cannot get it to idle smooth at all. When I mess With the carburetors fuel input and with the timing, advancing it to various different points no combination of that has gotten it to idle anywhere close to smooth (The idle RPMs very by as much as 150 rpm's). Is it possible that the distributor assembly has just suddenly gone wrong? If anybody has any other ideas of what I might try I'm open to anything at this point. Sorry for the incredibly long description but there seems to be many variables involved with this problem and frankly it's about made me lose my mind! Thank you in advance for anything that might help!

1 Reply

HMAC300

MECHANIC
48,601 POSTS

I know I answered this last week I think. Does this have a fuel regulator on it? Check your fuel pressure and then your volume, you should get about a half pint in 30 seconds. Put a vacuum gauge to the intake and see what your vacuum reading is it should be around 20" at idle. You should really find out what the heck is in this engine and do a compression check on this. If there is a 20% variance between cylinders then find out why. Your distributor could have slipped time however. With the advance you are saying you put in this i'd bet this has a much larger cam than what was stock because they never ran with that much timing advanced. Is idle the only time that you have the problem or is it other times while running. If you have a larger cam you may have to turn your idle up to around 1100 or 1200 rpm's cause it sounds more like now that you are having a valve overlap due to the larger cam and you need more rpm's to idle.