what kind of mileage is good? im gettimg 18.6 on my last tank.

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71 valiant 225, 904, 7 1/4
69 W200 power wagon 318, np435, np205, d44 front, d60 rear

If that's 50% highway, and 50% stop and go/light to light combined mileage, that's pretty fair....if that's highway only and it's a stocker, it's time for a tune up, and some carb and timing tuning. If it's 100% city,
and you are in a big city, that's really good...

-D.Idiot

that was about 50-50 city highway. im running a super six with a long tube header. i just changed exhaust, from an 1-3/4" system to an 2-1/2" cherry bomb turbo. i expected to see an increase in milage but i did'nt. i have tried several things to increase mileage. it was about 17.5 with the holley 1920 on it, went super six and still 17.5, K&N with cold air 17.5, HEI 17.5, NGK plugs 18.5, bigger exhaust 18.6,....anything else to try?

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71 valiant 225, 904, 7 1/4
69 W200 power wagon 318, np435, np205, d44 front, d60 rear

yea keep your foot out of carb....LOL...try setting valve lash...timing,maybe recurve advance

keep on roddin'

What is your rear end gear ratio?
and tire size?

I am running a stock motor at the moment and it gets 22.5 to 23.5 mpg driving 50/50 with P225/60 -14's and a 2.76 8 3/4 Sure-Grip. That is with a Holley 1920 and a #57 jet. Exhaust is 2.25". and 2" tail pipe.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

i'm getting anywhere from 15-18 right now. about 60-40 city/hwy. my lebaron is a heavy car, though, so i figure that's about right. it also doesn't help that it's winter time here in michigan. the cold always seems to take a mile or two away.

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1981 Lebaron with 225; all original, save for a door.

yes the cold and also winter gas mix...will take a mile or so

valve lash is set. tune up is great, it runs like a v8 and passes tail pipe smog. i am going to start playing with timing curve soon.
tires are a 205/70/14 and rear is a 2.76
i am really interested in what others are getting with what setup they have.

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71 valiant 225, 904, 7 1/4
69 W200 power wagon 318, np435, np205, d44 front, d60 rear

I may get clobbered here but here goes: I do not feel that the 2bbl carter used on the supersix combo is the greatest as far as fuel mileage goes.
If you could find a carb with the "dual booster" design (ala rochestor dual-jet OR (dare to say!) Ford 2 bbl, the both have this feature. Another good one would be a holley (small one) fitted with an anular discharge booster.
If there were a way to adapt the dual jet to a slant, I think this would be a very efficient carb for the engine for these reasons; dual dooster design, adjustable needle in the jets (called APT on a rochester) and very efficient idle system. the power piston is also tunable.
A couple more tricks for fuel MPG. manual trans mission, drum brakes set a bit loose, narrower and taller tires with more air pressure, optomized timing (lots of trial and error tuning) wider plug gap to fire a lean mixture at cruise and the hei conversion to the dizzy, front air dam under bumper, lower car all around and trim as much weight as possible, 100 percent accurate alignment paying attention to toe in and camber. Believe it or not, adding EGR to an engine can sometimes give a slight boost in mpg, ignition must be optimized also for the egr. I guess the next step would be fuel injection, multi-port of course. Also, if you went with the cast crank motor, this had a lighter rotating mass so that might help, but maybe not that much because the reciprocating parts did not get much lighter. (These are just my theories as I have been giving this alot of thought also).

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1979 W150 Shortbox
225, NP435, 9 1/4, Dana 44

The Good Life.

You're getting close to running out of options here. You've done good by doing the HEI conversion and using NGK plugs. Do you have a remanufactured or NOS carburetor on your car? You could be losing a few mpg's by running a remanned job. After that and a distributor recurve, things could start getting expensive. To the point where its just not worth it.

Here is a mileage timeline I did a while back.

http://slantsix.org/forum/viewtopic.php ... e+timeline

All my driving is 50/50 city/highway. I've had a best of 23mpg and my worst is 19mpg. My car on average sits right at 20.8mpg but I drive it normally and don't really ease on and off the throttle like I could be doing. I still need to recurve my distributor but I'm still trying to figure out how that all works.

It is very simple.......See the recurve thread under Engine FAQ. Lots of good info plus a 4 page guide on how to do it. My results are also posted in a spread sheet which you can down load and use your self.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG