MPG The Best Of Both Worlds

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skep419 said:
What would be the best mods to up the MPG?
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I have a 73 Duster, 3400 lbs w/o me, 408 Edel heads, M1, 9.8:1 static (about 8.7 static) comp, 236/242 hyd roller, 4000 Dynamic 9.5" conv, 727 manual reverse into a 3.73 Dana.

With the old Holley 750 DP, my best ET was 12.26 and 8 mpg.

With a 850 ThermoQuad, my best ET is 12.09 and I have gotten a best of 14 mpg on the highway at 65-70 mpg at 3500 rpm (minimal converter slippage).

So... Get a spreadbore carb, esp a Thermoquad. When set up right, it has excellent low end torque, gets good mpg, and flows enough for my motor. I love mine, but then I get to tinker with it a lot. These carbs are very sophisticated as compared to the Holley, and require a lot more skill to set up propoerly. Thus, most people hate them. Oh, and they can have slight leakage (into the manifold) issues. An A/F wideband gage is a must.

Oh, and I got the same MPG from a Edel 1406 (600 cfm) as the TQ, but it dropped my ET over a second - not enough flow.
 
mopardude318 said:
I just bought a 500 dollar 93 toyota celica today!!! I'll start my own thread.
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30+ years of fart knockin around with cars and one thing I have learned is that the best mod for any old Hot Rod is having nice, easy going driver as a second car.

Your "driver" can be whatever you want it to be……. /6 Dart, 93 Toyota, 2010 BMW…… Doesn't matter. As long as it is in your budget and reliable.

This frees up time and money for your project. My Barracuda gets 10mpg on the highway but I don't care because I have other options.

And again….. If I want to take 3 weeks changing the spark plugs, I can because my toy only has to look cool, it doesn't have to be relied upon as daily transportation.
 
1968FormulaS340 said:
30+ years of fart knockin around with cars and one thing I have learned is that the best mod for any old Hot Rod is having nice, easy going driver as a second car.

Your "driver" can be whatever you want it to be……. /6 Dart, 93 Toyota, 2010 BMW…… Doesn't matter. As long as it is in your budget and reliable.

This frees up time and money for your project. My Barracuda gets 10mpg on the highway but I don't care because I have other options.

And again….. If I want to take 3 weeks changing the spark plugs, I can because my toy only has to look cool, it doesn't have to be relied upon as daily transportation.
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in the past I have used my toys as transportation, what a freaking nightmare......using my old V-8 Ranger I had as a driver is what ended up slowly killing it.....
 
1968FormulaS340 said:
$500 Honda Civic as a daily driver.
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couldn't have said it better...



That being said, either a VS carb (I like Holleys) or check out the EZ EFI kits. Big bucks, but do a google search, lots of bow-tie guys having great success with power and MPG.

JOE
 
I have a 98 avenger for a work comuter and a 95k1500 for tow rug/winter 4x4. Like driving the dart but can only afford to drive it once or twice a week.
 
joeboy said:
couldn't have said it better...



That being said, either a VS carb (I like Holleys) or check out the EZ EFI kits. Big bucks, but do a google search, lots of bow-tie guys having great success with power and MPG.

JOE
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send fastmanefi a pm....
 
1968FormulaS340 said:
Hold on… Did you say you are only getting 96 miles out of a tank? That's not much more than 5mpg.
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Actually it would be 6 mpg assuming he ran it dry, which is 20% more than 5 mpg :-D

Likely he's only running out 14 gallons (2 gallons left), which would be 96/14 = 6.85 mpg. That stinks (or sucks, as opposed to sips), but not as bad as 5, but only barely not as bad.
 
jimmyray said:
Actually it would be 6 mpg assuming he ran it dry, which is 20% more than 5 mpg :-D

Likely he's only running out 14 gallons (2 gallons left), which would be 96/14 = 6.85 mpg. That stinks (or sucks, as opposed to sips), but not as bad as 5, but only barely not as bad.
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Holy crap!!! Sounds like it's got a leak somewhere. Pretty high fuel consumption for a fairly mild small block a body.
 
"What would be the best mods to up the MPG without sacrificing E/T to much.
Here is what I have.
Sell 360...400 big block that needs a rebuild in the garage ( more power at less rpm)

Edelbrock 750 vac sec carb. 3.23 gears (came stock with suregrip)

I have an appointment to get the Dart dyno tuned June 4. Want to get the best tune possible.

Swap carb and gears, buy a new cam?
Keep carb, cam, swap gears
Keep everything the same, tune "

Since you already have a 750 Vac Sec carb, try that, both milage and 1/4 mile time. Then the 3:23 gears, swap them in and see what milage and 1/4 mile time. Do things one at a time so you know what works and what does'nt. I also have to agree with the Thermoquad and vacuum gage. Also Wide Open Throttle never gives MPG, but I guess you know that.
 
Let me change the gas mileage part to,

What changes should be made to make my drive-train work as a team?
(make existing combo run better, faster, more efficient with same converter and gears)

Camshaft not right for combo? what would you recommend if that was the only thing changed?
 
Stock 340 cam or the replacement 340 cam
 
I wouldn't go any bigger than a Comp XE268 or Lunati 60403 (pretty close to the same cam's). Main reason is the compression is too low to really support anything bigger than that. A smaller cam like either of those will make a lot more bottom end torque than what you have. That will work better with your combination as a whole IMO. With a smaller cam like one of those you could also go to a 3.55 or 3.23 gear which combined with the cam and swapping to a vac sec. carb should increase the fuel mileage markedly.
 
Set your timing as advanced as you can without spark knock, and as someone mentioned earlier use the vacuum advance on your distributor. A good spreadbore type carburetor would likely help a lot too (vacuum operated secondaries). Simple things like a front end alignment, good radial tires inflated to the correct pressure, and a good tune-up will make a difference when it comes to saving gas. If you presently have a hood scoop on the car, make it fully functional or remove it as it becomes a huge source of drag.
 
Someone else said this also, but I'll say it again. Get rid of that piece of junk that passes for a carb you have sitting on top of that thing and replace it with a TQ, your mileage will double and it'll probably go faster as well. I know this from personal experience, same as the other guy, with a 750 DP holley it got around 10 - 11 to the gallon, with the TQ it got around 17 -18 and a couple of tenths faster.
The combo I have now is 360 making high 400's horsepower,ported Eddies 11:1 comp custom ground hydraulic roller mid 220's @.050" modded LD340 and an 850 TQ 3.55 gear 26" tyres 3600 TA convertor and it still gets 17-18 cruising around the city. It obviously drinks it when I get on it but driven lightly it is great on fuel. There is NO free lunch but you can have a bit of both!
 
"What changes should be made to make my drive-train work as a team?
(make existing combo run better, faster, more efficient with same converter and gears)

Camshaft not right for combo? what would you recommend if that was the only thing changed?"

For starters I would open it up and advance the cam you have 6°. It's too large IMO, but not unworkable. But you need more cylinder pressure. Next, the DP carb IMO hurts you economy wise and is no help with the high stall and gear you have. I'd get a smaller VS carb, even the oldschool 3310 would give an instant boost and be just as fast once tuned. Then rework the ignition and you're as good as it will get until you address the real issue which is no static compression. I'm figuring it just making 9:1 and it should be 10.5 with the heads you have and that cam. The pistons are wrong.
 
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