I bought my 1974 Dodge Dart as a fun car to tinker with, AND as a relief from the 11.5 MPG my Ram 2500 pickup gets. Since it's a 74, it's smog exempt here in CA so I can do whatever I want with it. I don't have the time or inclination to convert it to Fuel injection or turbo charge it, and I MIGHT consider a Super-6 setup IF gas ever drops below $3.50 in Los Angeles again, but for now, I am looking for bolt-on kind of suggestions that can be performed on a weekend afternoon and still get me to the bus stop on Monday morning. It's a 74 Dart 4 door, 225/904/(not sure about the rear yet) 4-drum power brakes, Power steeering, AC ("Needs charging" according to the previous owner). Also, it apparently wasn't an original CA car, because it doesn't have a smog pump (yay!)

So suggest away, but remember, I'm not looking for mor power, I'm looking for mileage.

Hi there, my thoughts would be HEI conversion, a good overall tune up, rebuild carb if needed, service trans, don't discount the super six conversion, I found it to be very economical as well as much better power. If the engine is good perhaps remove the head and skim it for better comp. cheers!

Bolt on is kinda tough.

To get started, accomplish the most overlooked tune up step. Adjust your valves.

A larger head pipe. Increase from the OEM 1-7/8" Noodle pipe to a 2-1/4". If you can find a factory Feather Duster or Dart Lite pipe, that will bolt on.
Replace the OEM Holley 1945 with a Holley Economaster 1920. This was an aftermarket replacement carb.

Make sure the EGR system is working right.
Make sure your mechanical and vacuum advance is functioning properly
Recurve the distributor to optimize igntion timing.

How long is your commute to catch the bus? What are the speeds? Any other specifics about your drive?

What is your fuel economy now?

CJ

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Part of Tyrde-Browne Racing

Ditto the above. Actually, I have found that the BBD can often get better mileage than the 1bbl, so that is a good upgrade for both power and mileage. Adjusting the carb is easier too, to improve mileage.

Lou

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Home of Slant6-powered fun machines since 1988

(1) Synthetic 0W-30 oil (or 5W-30 if you are nervous about 0 weight)
(2) an electric fan, a carb heat shield, a cold air intake system
(3) run the tires at the maximum pressure listed on the sidewalls
(4) run skinny tires on the lightest rims you can find
(5) remove any extra weight (seats, tools, spare tires, etc...)
(6) ditto on the trans service. Adjust the bands and make sure the kickdown is functioning properly
(7) install a vacum gauge and drive to maximize vacuum
(8) drive no faster than 55-60 MPH
(9) perhaps run the valve lash .002 looser than the stock specification
(10) front air dam/spoiler
(11) spoiler on the back of the roof and trunk edge to break up the air flow at highway speeds. Don't worry too much about this since aerodynamics is really a non-issue below 40-45 MPH.
(12) make sure no brakes are dragging and all wheel bearings are lubricated and adjusted properly

I can't think of much else that is a bolt on modification. There are more ways to improve efficiency, but they all require some part removal and modification or replacement.

Reed: I wouldn’t recommend this bit of advice. One needs to keep all of the tire tread possible in contact with driving surface. In other words, inflate enough to support the weight of car without distorting tire contact patch. Under inflation will cause two contact patches at outer edges of tread with little to no center contact, and over inflation will cause just center of tread to contact the driving surface; both result in decreased traction and dangerous driving dynamics, and short tire life.

Maximum tire inflation listed on sidewall has nothing to do with proper inflation for a particular vehicle. For a given tire, depending on a vehicle’s weight or load will dictate what inflation is needed. A light vehicle requires less air pressure, and a heavy vehicle using the same tire requires higher pressure as long as it doesn’t exceed max inflation listed. This why it is important to follow manufacture’s tire inflation specifications located on door frame sticker newer cars, and in owner’s manual.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

1. The simplest weekend type upgrade is uncorking the exhaust. Many of us have done this and it really helps low end torque and produces higher average vacuum readings which means better mileage. I start with a 2.25" head pipe and jump up to 2.5" at the HP 2 Flow Master and to the FM70 on back....
2. The second would be recurving the 74 distributor. Mine was a mess, sloppy springs, sticky advance plates and it pinged a lot. Now I run 10 degrees initial and 52-55 degrees total. It gives the engine a huge difference in driving feel and overall pep! Not a hint of pinging...
3. The third would be changing the air cleaner to a late 70's version so you can run cold ram air.
4. The fourth might be running a hotter HEI type coil and 8mm wires with a MO-3000 rotor (has a longer tip) and .045 spark plug gap.
5. The fifth would be opening up the valve lash .002 over stock for more torque.

I think Reed's list covers most of the upgrades on my 74 Swinger.

I am kind of breaking the rule on the tires.....running 7" wide aluminum rims and 28 pounds in the rear, 33 in the front. I like the ride of the P215 Toyo Eclipse P215 70R-14's.

Click on the red link below my name to view pictures.

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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

Ted,
On the tires, why 28 in the rear and 33 in the front? Wouldn't lower inflated tires on the rear cause more rolling resistance? I'm curious because I'm trying to get those same high mpg's as you.

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70 Plymouth Valiant 4dr

The rear is providing motivation for the car so the more contact patch the more usable torque the drivetrain is placing to the pavement...if you over inflate the fronts a little you get less rolling resistance since they are literally being 'plowed' into the tarmac by the rear end...

Kind of similar to what street guys do at the track to get a little more out of their car on the 1/4 mile...

-D.Idiot

ValiantBoyWonder,
In theory I suppose that might be true but, the Dart is super light in the rear. All the weight is on the front.
Yes, to what DI said......it works well and runs fine with out any hit on mileage.
Those are cold temps.....after a little driving they come up 3 pounds.
So it is 36 in the front and 31 in the rear.

In the winter I run P215 70's on the front and big 60 series BFG's T/A radials on the back that are sipped as snow tires. Works awesome on all the black ice. They really make the car stop straight. I travel on the back roads all along the foothills to and from work. With 28 in the rear they wear better too.....The 60 series BFG T/A radials hold their shape very well and don't need a lot of air. I have gone as low as 25 lbs. on super icy conditions.

In the summer, I run P215 70's on all four corners. Same pressures.

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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

Fuel economy is all about reducing frictional losses and optimizing the engine for fuel efficiency. An important loss that can be easily reduced is pumping loss.

Ted suggested ram-air for improving fuel efficiency. It is important to have a cool-air supply that includes a working heated air inlet system. Besides helping to vaporize the fuel, warm air REDUCES the engine's volumetric efficiency at part throttle which in turn allows the throttle to be opened wider, thereby reducing pumping loss.

It is also important to keep the EGR system in good working order. Besides reducing combustion temperatures to allow more ignition advance with lower octane gasoline, EGR also reduces pumping loss by lowering the engine's volumetric efficiency at part throttle.

Keeping the manifold heat control valve in good working order also helps fuel economy and reduces engine wear. Keeping the intake manifold cool is better for maximizing power and this works great at the drag strip. However, for street-driven cars, having a hot-spot in the manifold floor under the carburetor vaporizes any fuel that falls out of the airstream. Vaporizing gasoline produces a refrigeration effect and this will cause the intake manifold to become cold without supplemental heat. A heated intake manifold will improve engine operation even in Furnace Creek in July. If you've switched to headers, use water for heating the intake manifold. Keeping the carburetor cool is always a good idea.
http://www.youtube.com/watch?v=5w6f7i2151k

The cooling fan absorbs a measurable amount of power and is not required at highway speeds. A few members have even removed their cooling fans but I think it would be better to replace it with a thermostatically-controlled electric fan. Since slant-six alternators have marginal outputs, it would be wise to upgrade to a Denso alternator at the same time.

As for tires, Barry's Tire Tech recommends using a tire that has good wear characteristics (overall lower cost of operation) and running at 3-5 psi above the placard recommendation and not higher than the maximum pressure rating on the sidewall. Also, it appears that using a tire with a higher load rating reduces rolling resistance more than the aerodynamic resistance from the extra width. I would be very careful about changing the relative pressures of the front & rear tires as this can affect handling.
http://www.barrystiretech.com/rrandfe.html
http://www.barrystiretech.com/rrandfe2.html

Regarding engine oil, there are pumping losses from excessive viscosity. Unless your oil runs extremely hot, a 30-grade oil (0W-30, 5W-30, 10W-30, 30) will be suitable in most cases. 0W-30 oils are generally synthetics, which means that they don't thin-out as quickly with increasing temperature and don't thicken as quickly with decreasing temperature. Unless you are burning very little oil, it would be overall cheaper to stick with a 10W-30 HDEO.

Upgrading to the HEI ignition system is also a good idea. The HEI system allows the coil to be fully saturated up to around 4000 RPM on a 6-cylinder, which ensures a hotter and longer spark than the Chrysler Electronic Ignition while eliminating any chance of primary resistor failure.

How much better is HEI over a Pertronix ICM vs Chrysler EI vs stock? I get 8,000kV with a Pertronix which seems low.

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Leela: 1970 Dart 225 CID
Coulmn Shift TorqueFlite
7 1/4" Axle 2.76 Gears

Go ahead and save that weird car, the sedan, the 6 cylinder, the C-Body. If you want a big block musclecar and that's all you care about, your missing the point.

Nicely said Frank!

That really covers the bases for what I have done over the past few years.

The thermostatically controlled electric fans with an air dam under the car really provide a nice balance. They rarely turn on in the winter. Only after I shut off the engine. They really aid in speeding up the warm up time for the engine and produce good cabin heat. I am sure that helps mileage since the choke kicks off much quicker.

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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

Had the pertronix in my 68 valiant with a well adjusted Holley 1945 and a Carter bbs. With both carbs I had fouled plugs. Did the hei setup with good junkyard parts for $25. Best upgrade ever! I've installed and used a few mopar electronic ignitions. There okay but look at what your eliminating with the hei. An ecu that can get hot and melt the potting material leaving a mess on the inner fender. A ballast resistor that when it goes out leaves you sitting on the side of the road (how many parts stores still carry good quality replacements). You can buy hei "upgrade parts" off the shelf (not that you need to factor is good enough).