I am sure there are probably a million answers to this but I am trying to just get a feel for the range of possibilities. What should I expect for gas mileage with a stock slant six with a single barrel Holley 1985. Valve train is hydraulic, automatic transmission, electronic ignition. Right now I am getting around 10 1/2 mpg in town. Thanks.

Mike

How heavy is the vehicle?
10.5 is low, most SL6 passenger cars get 16 to 22 mpg without much trouble.
DD

1973 Duster = loaded with 200 lb guy, and tools/ spare tire/jack...full load of gas....3455 lbs...

Holley 1945
Hydro motor
A904 Automatic
stock 2.76 rear gearing?

time to check your timing, check your vacuum, and make sure the chake plate pulls off...

-D.Idiot

I have previously checked for vacuum leaks and found none but one more check won't hurt. The choke plate opens fully. The timing is at about 12 BTDC. Should I retard it some? Thanks.

Mike

The old crusty wiring in these old cars is one of their major weaknesses now. Check the voltage on both sides of your ballast resister. The high side should be at least 12.5 volts. If it drops much below that, your ignition will not work correctly. The low side should be around 8 volts. Old connectors sap voltage through the harness. If you are low, check your battery, and see if it is carrying the required 13.5 volts while running. If the battery is up, and the resister is not, then replace all or part of your primaty ignition wiring. Use your VOM to track down where the bad connectors are. Start at the alternator, and work your way through the system till you get to the ballast resister, and then, finally the coil. My '69 Dart went from 13 to 18 just with replacement of the primary ignition wiring. It took several hours, and was well worth it. One of the major culprits in the system is the old amp meter, since all current flows through it first. I finally eliminated the AMP meter, went to a volt meter, and bypassed the amp meter.

Good point on the electrical, I know I usually overlook that when looking at mileage. This time though I had done a complete redo under the hood. Every component of the underhood electrical is brand new...harness and all the charging and starting and ignition systems. It all checks out. I am suspecting the timing is too advanced and/or fuel mixture too rich. Anybody have preferred timing settings and carb settings? Thanks.

Mike

I thought I saw you on the road the other day! Glad to see it's coming together.
You might want to take a look at highway mileage, too, to reduce the human and acceleration factors in the equation. Luckily, those of us in Lubbock don't have to look hard for a nice, straight, flat road, do we? Maybe a run down 84 to the Caprock above Post and back?

Yes, it has been running steady now for a couple weeks. I still have a few minor things to mess with besides the body. Basically though, it is doing great. I just need to keep tweaking it to see if I can improve the mileage. Maybe one of these nights, I can go out on cruise night if I am in town. Heven't done that in awhile.

Mike

Good for you for doing the wiring, but I would still put a VOM on the coil and see for yourself what the voltage is there. You know what they say about "ASSuME. Your timing is about right. You could reduce it a couple of points, but that probably would not amount to much. Check your vacuum advance pot, on the distributor, and see if it is functioning. It should change the timing by the amount stamped on the arm of the pot, and should start to advance the timing at about 8 inches of vacuum on a stock slant. You also should be getting 15 MPGs around town at a minimum. My 360 Dart gives me 22 MPG on the highway with an OD 4 spd, and my Slant Dart has given me between 26 and 29 MPG's on the highway with a T-5 five speed. With the auto, it yeilded 22 on the highway, and 18 around town. Good luck.