My daily driver needs some work so I want to make my 70 cuda my daily for a few weeks. It has a 69 383 engine from a truck. It was rebuilt about 8 years ago and thats all I know. I do not know the cam or anything but I would imagine that it is all close to stock. Im running headers hooked to dual exhaust, an automatic transmission, 2.76 gears because I drive on the interstate occassionally, mopar electronic ignition. Where should I aim to set my timing at on this? And as far as a carb I have factory square bore and spread bore intakes. I have a 600 edelbrock and a few thermoquads around but they are early 80s carbs. Also have a 750 holley vacuum carb. What carb would be best for decent gas mileage? Id really like to get to around 14 or so city mileage if possible. Right now I get considerably less than 10 mpg. Thanks for the help.

less than 10 mpg w/ a stockish 383 and 2.76 gears? You have some other problems. I got 13-14 in a supercharged 440 w/ 3.91's. A 625 carter would work fine. If you want mpg the 600 will work but you have to get that thing tuned. I'd try your timing in full at 2400 and at 38*. By a vacuum gauge and a good timing light.

Where do you live?

The 600 Eddy should get you the best MPG.

You have problems if you get under 10 with that setup. Light car and high gears.

I agree with the above. I have a good light and I can meet you in Louisville, Lex area or even Morehead. Might have an tuning kit for that 600 Eddy.

For the carb: I'd suggest the thermoquad on the spreadbore and for the dist: 1st-more initial maybe ~12 to start (checked w vac adv disconnected) and experiment for the best initial (might use the vac guage method) and toss the thick spring w the long loop and replace w one of the light ones in the MP cellophane kit then shorten the slots to get ~36 total (again w vac adv disconnected) and you want the right combo of stiff/light springs to keep your eng just under the pinging point in your everyday driving style THEN hookup the vac adv & tune it to also stay just under the pinging point at a steady speed light throttle at a rpm where the springs are already maxed out. Only caveat is iirc TQ"s are manifold only. Set up the timing before the carb and do the dist sections in order and get each one near perfect before moving on to the next one. I'd have Demonsizzler here on Moparts rebuild/set up a TQ for you.

Your ign timing curve is very important for MPG. You will want a minimum of 15 degrees initial, probably more like 18*. You need to throw out the FSM thinking about timing. First off you need to find where your engine wants it's initial timing, disconect the vacume advance, set you idle mix screws to get the highest vaccume possible then advance the distributer from the stock setting till you get the highest vaccume reading then back off 1 or 2 degrees till it starts to drop then record what degrees it is at. Then you need to take that away from about 38 or 40 (max advance will be around 38-40 degrees)to find out how much advance your distributer needs to be set up inside. Then if you have the stock type distributer pop open the distributer and look at the number on the advance mechanisim, the number should be doubled to see how much timing advance it will give you. If it says 10 you will get 20 degrees advance and you should be real close, if it is a higher number you need to shorten te slots, if it is a lower number you need to lengthen the slots. Make sure the advance thingy can turn easily both directions on the distributer shaft, if not fix it, if it turns easy put the springs back in and make sure they pull it all the way back to the stops, then put it back together and install it back at the same initial timing setting you found earlier (around 18* or so) then you mechanical timing is set for best MPG, also while you are in the distributer make sure your vacume advance can is working and hopefully it has a low number on it like 5-9 that is the degrees advance it gets and it is also doubled at the crank, I have found through lots of testing that mopars like vaccume advance but not much when the mechanical advance is set right.

After you get that done I bet you will pick up a couple MPGs over the stock settings.

Then it is onto your carb, I like the factory AVS AFB and thermoquads, they can all deliver good MPGs and are all easy to tune, I prefer the t-quad but admitedly are harder to tune than te aluminum carbs. Basically set the idle mix screws for the highest vaccume setting and then lean out the midrange till it bogs and then richen it back up one step either a one size bigger jet or one size smaller main metering rods.

I am in Somerset which is about 75 miles south of Lexington.

With your low gears, your RPMs will be so low that the the distrubitor probably never sees full advance? I would work on recurving the distrubitor for more initial advance, and make sure the vacuum advance is working.

The Edelbrock 600 should be fine. Depending on how the car runs, you could use weaker step-up springs (keeps the thicker part of the metering rod in the jet longer.)

Get the timing curve sorted out right, both the mechanical and the vacuum advance. Then start tuning the carb, pick up a jet/rod tuning kit if you don't already have one. Stick with that 600 edelbrock. Yes the t-quad is a great carb for mileage, but if you have a good running eddy 600 on there now, just leave it instead of fighting with the tqquad.

At idle it smells really rich... but the plugs are white so maybe it is leaning out after idle? And is this the tuning kit I need? edelbrock 1487

Tune the mixture screws.

Might need stiffer springs under the rods, but I think they are pretty stiff from the factory.

Does sound like it is lean. Easy to put smaller rods in there with the kit.

If you want to bring it to Morehead, I will be there for much of the next month.

I may even have the kit, but that is a long shot. Been years since I had that model carb.

IF you have a nice clean TQ ..try that. You can adjust the primary side with a simple screw-driver !!

I have not found lower gear to help city miledge, they only make the car more fun to drive.

A lot of work is lost in an engine pulling pistons down with a lot of vaccume over them, running a higher gear means you have to push the throttle harder and that means less vaccume in the intake and over the pistons pulling them up while the crank if trying to pull them down. The only problem becaomes if you are running the engine so slow that fuel seperates from the mixture before it hits the cylinder, of course with the little bitty dinky ports in a stock big block head you can run a 383 pretty slow and still have some decent port velocity.

A little more obvious problem with the higher gear if if you just hammer it all the time and make it stay in a lower gear, then you lose the benifit of the higher gearing.

I have a set of 3.23s but I really like the 2.76s because I drive on the interstate a bit. Ill order that kit and try to get the carb tuned right.

Another thing.. this engine has always been pretty weak. I swapped some 3.23s today and its still horribly slow. Id be afraid to race my grandparents 97 voyager lol. This engine usually idles really nice and smooth at 600 rpm or so. Just is a dog at all rpms