Watch this:

Jebby

 

Quack...some data points for comparison;
1969 M-21CR 3.70 L-46 (350/350) 15mpg going downhill, going uphill, with a tailwind, with passenger, with martian pushing...remarkably the car just gets 15 mpg allatime.

1982 CE fuelie 700R4 .70 th overdrive with lock-up 2.87 rear = 20 city 26 hyway about 24 mixed use.

The last time I got 9pmg was with my much heavier and big and larger engine 1969 GTO Ram-Air 3 car with a TH400 and (I think 3.50 rear gears)

So there is something definitely wrong.

Vacuum leaks
Throttle shafts
wrong jetting
dragging brake?
wrong timing?
thick oil 20w 50??? thick synthetic oil not letting the engine break in?)
Not broken in yet?
Speedometer wrong gear/ odometer
Tires of a weird size
Running too cool

Unkahal

 

I couldn't stand it and had to purchase the Inova timing light and picked up a vacuum gauge as well. After adjusting the idle mixture screws and got the vacuum as good as it was going to get(20 "hg). I did a timing check???? Tomorrow I will reset the distributor and do the adjustments that Lars was so kind in forwarding to me. I did however pull #1 and #2 plugs and inspected them. Did not have much carbon build up. I was expecting it to be really dark. I will post about fuel consumption from the adjustments that I made. Thanks for the comments and suggestions.

 

Tell us your timing readings. Should be around 12 idle. 34-36 at 3000-4000 no vac advance and 40-something at 3000 light load with vac hooked up

 

Not enough light-load cruise advance is biggest waste of fuel

 

Before I removed the distributor the readings I had gotten with the new timing light was = at idle with vac. connected was 16* at 685 rpm and ran it up to 3200 and the timing advanced to 58* back at idle I pulled the vac. tube off and did not see a difference. Lars instructions was to attach the vac. to an intake port and not the timed port on this Elderbrock carb. I pulled and reinstalled the distributor after setting the timing mark at 12* as Lars had instructed and set the timing with vac. disconnected at 36* and 2900 rpm. all went well. ran it up to the 2800 rpm range a few times and timing followed as Lars indicated it would. I did have to adjust the idle a little but that was in the instructions as well.
Still had a few things to do, but I couldn't help myself. I was like a kid in a candy store and I just had to give her a short test drive. Instructions tells you to do some quick acceleration trials and listen for knocks or pings, and if so, adjust accordingly. I had none and the engine ran really well without any bogging or misses. Now I did relocated the acc. pump linkage to the normal range on the carb as Bubba had it on the lets go fast spot, but right now I am into cruising and maybe a little better mileage that way.
Just to let everyone know, if you purchase a Inova 3568, which runs about $100 go ahead and prefab an extension power lead, the leads that come with the light is to short from the battery to the front of the engine. Another note, your RPM gauge in your dash may not be reading correctly, My rpm showed 500 to 550 but was running 775 on the timing light.
I'll post the MPG when I do the fuel test.
Ya'll have a great day!

 

I recently bought the Inova 5568 (has lead for dwell) and I picked up a 12v source at the back of the alternator (under the rubber boot).

 

Sounds like you are well on your way to getting it sorted out with great information from the experts here.
I caught 3 changes you made already and each of them should have a very positive effect on gas mileage

• Leaned idle /cruise mixture screws down by 1 whole turn
• Hooked up vac advance to engine vacuum
• Got mechanical advance set correctly

 

After I finished with the steering column I finally took it on a little cruise to check the mpg after the adjustments and changes I made. Removed and set distributor in correctly, adjusted the idle mixture screws, connected vacuum advance to manifold and got off the timed vacuum, and set up the timing as Mr. Lars instructions. I calculated and went from the 8.3 to 11.6 mpg. That is a great plus. I will check vacuum and adjust idle mixture screws a little more?? I also wasn't aware of the lock up on the TC. I am in the middle of determining if it is actually working. Thanks for the info you guys provided to help me along!