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Paul491
1971 Dodge Dart 225/6
1973 Dodge Coronet Wgn 400/8
1958 Shasta "Canned Ham" Travel Trailer
1984 Porsche 911 Carrera M491 Cpe 3.2L/6

Which midrange comp cam? A 252 duration would have provided the best torque and gotten passable beginner performance and solid 21-24 mpg highway if everything jived (I got 24 because I used a manual transmission). If it's the 264...you may lose a little mileage although I have seen people get about 21 mpg highway with certain combinations.

What I don't see here is Electronic ignition and or Distributor Recurve which will help both power and mileage (the stock points distributor leave much to improve on). Think of it as the icing on the cake for all the other stuff (come to think of it, no street porting of the head either? That's some efficiency left on the table too...)

In either case and with every engine it's give or take...if you want performance you give back some mileage...if you want mileage cut some of that fun acceleration out....

-D.Idiot

Hmmm, for best gas mileage.

Use the Dart for the car shows and cruises, buy a new, modern, 4cly car for the extended road trips. You and the grandkids will be happier.

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Paul491
1971 Dodge Dart 225/6
1973 Dodge Coronet Wgn 400/8
1958 Shasta "Canned Ham" Travel Trailer
1984 Porsche 911 Carrera M491 Cpe 3.2L/6

Believe me as much as we'd like a new car, it's way above my pay grade... At this point, I'm very thankful to have the Dart.

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Paul491
1971 Dodge Dart 225/6
1973 Dodge Coronet Wgn 400/8
1958 Shasta "Canned Ham" Travel Trailer
1984 Porsche 911 Carrera M491 Cpe 3.2L/6

What I don't see here is Electronic ignition and or Distributor Recurve which will help both power and mileage (the stock points distributor leave much to improve on).
Good question, D! Where can I go to find out about Electronic ignition and Distributor Recurve?
[/quote][/quote]
Look thru here http://www.slantsix.org/forum/viewtopic.php?t=38446
and here http://www.slantsix.org/forum/viewtopic.php?t=38465

Dave

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86 Miser 170,000+
2 1/4" exhaust
Holley 1920 #55
HEI MSD BLaster 2
17.8 mpg

1. Most folks will tell you 2.25" on the exhaust system from the exhaust manifold to the bumper. I ran that set up for a number of years with many different muffler combinations. After a lot of experimentation I found that I can run higher vacuum numbers with the 2.5" system with the two Flow Master mufflers in series, HP2 in front and a FM70 in the back. This is a tuned system that Flow Master suggested for the SL6 in my 74 Dart Swinger. There is little to no exhaust sound at cruise. All you hear is wind noise. Best exhaust sound is a perception. Some prefer no sound. Other like some. You can tune the sound with the rear muffler when running a 18" HP2 FM up front. The HP2 FM knocks out all the nasty resonance that a SL6 produces with the internal dual cones. The HP2 FM was actually designed for airplane emgines. The higher average vacuum numbers I see at cruise equates to better mileage. More power for going over the mountain passes with out having the pedal buried so that the power valve is on. Longer lash .012 and .022 provides more torque as well for better mileage. The distributor recurve is key to getting as much advance as you can at the right place in the torque curve which equates to better mileage.

2. I live in the foothills along the Cascade Mountain Range with lots of elevation changes. With a good distributor recurve you can make great mileage with 2.76 gears and 26" tall tires. You can get even more mileage by lightening the car. Best over all mileage for me has been keeping the engine at 2500 to 2600 rpm. So I have tuned the distributor recurve to provide 55 to 60 degrees advance at that rpm. Running high advance provides the most torque.

You should document vacuum and rpm readings at cruise and log your mileage before making any changes to establish a good baseline. Then make changes one at a time to track mileage changes. I keep a log book and used to drive 120 miles a day for documenting all my changes. Currently I only drive 64 miles a day. Hope this helps!

My worst mileage driving locally is 22.4 mpg. That is little to no freeway driving. When I get on the freeway, mileage goes right back up.

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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

Answer: The engine has a Comp Cam 252 with .453 lift and I think the head was milled .010

What can I expect for performance and mileage?

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Paul491
1971 Dodge Dart 225/6
1973 Dodge Coronet Wgn 400/8
1958 Shasta "Canned Ham" Travel Trailer
1984 Porsche 911 Carrera M491 Cpe 3.2L/6

21-23 mpg, slightly better than stock performance if the engine was milled to get a 9:1 SCR...a stock engine with a .010 mill is a stock 8:1 engine and takes no advantage of the cam or increased carburation...


-D.Idiot