Okay, first I have an Autozone "Actron" brand Dwell/Tach/Volt/RPM meter. It has no selector switch for 6 or 8 cylinder, but has all scales listed on the face of the meter. From all I read, to check dwell I should be using the 6 cylinder scale, however should I also be using the 6 cylinder scale for my RPMs? I need to make most of my adjustments @ 500 RPM in drive and I want to check the accuracy of my factory tach. The owners manual doesn't help.
Second question. My car @ idle was emitting strong gas smelling exhaust that was whitish/greyish and burned the hell out of my eyes. I checked all the carb adjustments including the mixture screws and everything was okay, so I checked my timing and it was way off spec. It reads like 14*BTC base so I turned it back to factory spec 6*BTC base and the exhaust gas problem greatly cleared up but not 100%. Could it have been that the spark was firing too early, there was that much unused gas and that was all coming out the tailpipe? The only problem now is I have a very slight rough idle, but timing, carb, plugs, o2 sensor (heated), cap and rotor are all adjusted to factory specs or brand new. Can a major exhaust leak cause a rough idle?
Thanks
For specs see sig.

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1983 T/A LG4 w/T-tops
Rebuilt/Modified E Q-jet
Custom Dual Ram-Air
Self painted cherry red w/ restored black/grey interior
Dynamat from firewall to tail wall
Welded Comp Eng SFC
Tokico Struts/Shocks
Hotchkis LCAs and Panhard Bar
Energy Suspension bushings all around

[This message has been edited by Nightcruzer (edited June 27, 2001).]

 

You have an 8 cylinder engine so you need to use the 8 cylinder scales on your meter. The one exception is if you are measuring the mixture control solenoid's dwell; read on the 6-cyl scale for that regardless of how many cylinders the engine has.

Your car will run vastly better with the timing advanced as far as it will go without causing pinging. What you did by retarding it was to reduce the idle vacuum, which made the carb feed less fuel overall at idle. You also reduced your performance and gas mileage. The spark being "too early" will not cause incomplete combustion; on the contrary, it improves combustion.

More than likely the plugs in the bottom of your carb are leaking. They have vacuum on one side and the bottom of the fuel bowl on the other; so if they leak, raw liquid gasoline gets sucked into the manifold, bypassing all metering in the carb. This is extremely common in these carbs: I'd estimate that somwhere between 80 and 90% of all Q-jets older than about 10 years that I've ever worked on have had this problem.

Turn the carb upside down and take the throttle plate off. The plugs in question are not the big round ones the size of a dime under the secondary jets; they are the 4 smaller ones that are on 2 tower-looking blobs of casting near the front of the carb, which are probably all crusted over with dried fuel crud from leaking and invisible. Take a wire brush and/or sandpaper to them and the area all around them, clean the exposed fresh metal with lacquer thinner or carb cleaner, and epoxy over them. Let the epoxy cure completely before re-installing the carb. Then the carb will actually be able to control the idle mixture.

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