Gas monster

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plymouth1937

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Hi my truck is roening me on gas cost its a d200 -68 whid a 400 bb 727 11" turbine shift kit dana 60 stock ratio ported stock heads headers Eddy singel plane intake holley 600 vac carb 68 main 4.5 power valve new proform ign set at 18 in 42 total no vac no pinging stock pistons low comp i think the cam is the Akilles heal have no specs but sounds nasty in idle suspect its a 268 or 272 comp cam but far from shore runs realy good lots of power iv made a 100km run onley hiway 55mph average 2.2l/10 km no load just me and the dog thats a lot in my book what to do

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Cam specs would help. Lots of knowledgeable members waiting to help you, if you provide more details. Cool old school truck!
 
Probably has a 4.10 gear in the back. Swap to 3.54 might help. That and a little tuning might get you 10MPG. Good luck and cool truck!
 
Factory HP Thermo quad and manifold would probably increase both gas mileage and HP

imo.
 
plymouth1937 said:
2.2l/10 km no load just me and the dog thats a lot in my book what to do ]
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2.2 what? liters/ quarts/ pints/ cc/ gallons/ tons/ pounds?

LOTS of low deck Mopars (then 383s) delivered decent mileage "back in the day." The only reason the 400's were poor in their day is that they were built in the midst of the '70's smog junk, were low compression and aweful cam timing.

Pull that big cam put in a "stock" cam and take a look at the timing curve. Depending on how the carb is jetted AND THE REAR RATIO AND TIRE SIZE there's no reason in "Murican" thinking those girls should get at least 14 MILES per GALLON whatever that transfers to in your end

"Real life" old world example: Back in the day a bone stock 69 Roadrunner 383 4 speed would have come with 3.23 rear gear. You could expect 15MPG or better out of those and they were considered a performance engine. Those WERE high compression
 
mopar head said:
Hot rod or gas sipper, your choice. If you want economy put in a 2bbl 318.
I know you guys probably pay out the *** in gas over there.
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67Dart273 said:
2.2 what? liters/ quarts/ pints/ cc/ gallons/ tons/ pounds?

LOTS of low deck Mopars (then 383s) delivered decent mileage "back in the day." The only reason the 400's were poor in their day is that they were built in the midst of the '70's smog junk, were low compression and aweful cam timing.

Pull that big cam put in a "stock" cam and take a look at the timing curve. Depending on how the carb is jetted AND THE REAR RATIO AND TIRE SIZE there's no reason in "Murican" thinking those girls should get at least 14 MILES per GALLON whatever that transfers to in your end

"Real life" old world example: Back in the day a bone stock 69 Roadrunner 383 4 speed would have come with 3.23 rear gear. You could expect 15MPG or better out of those and they were considered a performance engine. Those WERE high compression
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I wrote 2.2l the small l is for liter yes i think its 4:10 but i have 32" high 15" tires in the back so the rpm is about 3100 at 65mph the price för 1 liter 95 is 2 dollar i have curved the dist and i agree cam swap is the solution to the problem
 
3.54 gears, stock HP cam, TQ carb and intake. About as good as you can get without major work. Decent balance of power and mpg.
 
a low compression 400 with a 268/272 cam and 4;10 gears certainly doesnt need 95 fuel. whats your regular's octane #? changing to 3.23 or 3.55 rear will make you a lot happier.
 
plymouth1937 said:
I wrote 2.2l the small l is for liter yes i think its 4:10 but i have 32" high 15" tires in the back so the rpm is about 3100 at 65mph the price för 1 liter 95 is 2 dollar i have curved the dist and i agree cam swap is the solution to the problem
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3100 at 65 is somewhat high (for mileage) My old 70RR with 3.54 used to run about 3K at 70 and I would not wanted any higher

If I did the conversion right you mileage is about 10.6 miles per gallon. Yea. Fairly dismal, although there were LOTS of stock pickups getting only maybe 12 mpg "in the day." But many of those were 3/4T and 4x4 and so on

Can you go to larger rear tires? I say change the cam, check the distributor curve and timing, read plugs to see what the jetting looks like and BE READY to put a taller hear in the rear axle
 
2.2L is .58 gallons. 10KM is 6.21 miles. So I'm seein over 12MPG right there. I'd say it's about right.
 
Ditch the rumpity rump cam, ditch the single plane intake, and put vacuum advance on it and bring in 10 more degrees of timing at cruise. You’ll get much better mpg.
 
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TT5.9mag said:
Ditch the rumpity rump cam, ditch the single plane intake, and put vacuum advance on it and being in 10 more degrees of timing at cruise. You’ll get much better mpg.
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Pretty much.................
 
6.21 divided by .58

You can even estimate this, "about" 6 miles / "about" .6 is 10
 
Thanks for all tips what aftermarket cam is comperebole to a stock cam,cant bump up the ignition any more then 42 at 2200rpm pinning at 45 same whid initial tryed 20 but was kicking back plugs looks perfect this is my daily driver so avery gallon counts will try to bye a stock intake but the truck runs realy good lights the tires like on butter
 
plymouth1937 said:
Thanks for all tips what aftermarket cam is comperebole to a stock cam,cant bump up the ignition any more then 42 at 2200rpm pinning at 45 same whid initial tryed 20 but was kicking back plugs looks perfect this is my daily driver so avery gallon counts will try to bye a stock intake but the truck runs realy good lights the tires like on butter
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It won’t take any more ignition under hard acceleration, but light throttle cruising it will likely tolerate much much more. Like in the 50s. And gas mileage will go up. Start learning about vacuum advance and how it works. It will not effect high load, on throttle ignition timing.
 
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