Fuel economy issues

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273 said:
IMO 1-3 mpg increase is all you can ask from your EFI upgrade, I think your gas mileage problem lies else where cam, gearing and or tranny etc...
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I completely agree with you, except that dropping in a magnum with the EFI from the vehicle, highway is something like 20mpg would be around a 10mpg upgrade for me right now.
Well the trans has decided to crap out on me today, won't shift at times and is slipping like mad. I'm going to be taking the car to a shop to get it worked on and see if they can do anything with it. If they can't without too much money or trouble I'm going to drop a magnum in. Once I get an update from them I'll post it.
 
If a carb is so great why did they become dinosaurs?? Even the bulk of 2 wheel vehicles are now injected.........Nothing wrong with moving on...
 
Main reason car manufactures went fuel injection was cause of emission.
 
Seriously doubt that you will ever get a carb to run these consistent air/fuel ratios....and then IF you do as soon as the conditions change it will change as well....
 

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7dswinger said:
I completely agree with you, except that dropping in a magnum with the EFI from the vehicle, highway is something like 20mpg would be around a 10mpg upgrade for me right now.
Well the trans has decided to crap out on me today, won't shift at times and is slipping like mad. I'm going to be taking the car to a shop to get it worked on and see if they can do anything with it. If they can't without too much money or trouble I'm going to drop a magnum in. Once I get an update from them I'll post it.
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So the transmission might have been one of the reasons for bad mpg . Makes sense , my 340 gets over 23 mpg on the highway , so you should be getting better than 15 mpg .My setup is 340 , 3:55 83/4 , 727 , with 235/60-14 tires out back . Makes 413 hp 398 torque .
Good luck hope the 360 gets better mpg , it should with a good transmission
 
Jerry6: Ya I think it may be part of the reasons. If I was getting 15 I would't thinking engine swap haha, I drive 40 miles and use 6 to 8 gallons of gas, on a highway too.............

InkJunkie: I agree, carbs are great for their purpose but for efficiency, MPG, tuning and actually I think performance as well, EFI is the way to go, IF you can go that route and want to.
I think that car companies went to EFI for that reason and because they could dramatically increase performance without generating poor emissions.
 
inkjunkie said:
Seriously doubt that you will ever get a carb to run these consistent air/fuel ratios....and then IF you do as soon as the conditions change it will change as well....
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There are advantages , but try fixing a broken down efi on the side of the road . A few times my carb broke I was able to get it home for repairs , EFI on my new cars , it goes it's the tow truck and new parts =big $$$ .
Would like a new bolt on 6 speed auto though , I get over 23 mpg on the highway now , with a 6 speed it would be more like 30 , and city mpg would increase as well , efi , not sure it would be worth it performance/cost/economy wise .
 
I'm not saying FI isn't better than a carb but a well setup carb is hard to beat for power,mpg and cost. The OP went from 7 mpg to 8-10 mpg that's a 12-30% increase what more do you want from it. The 70's & 80's had some the worst HP & mpg car. Now with fuel injection along with OD, now variable cams etc... Where getting some high powered, higher gas mileage, emission friendly cars and trucks but with all that tech the Hemi truck only gets 20 mpg in town and my dad old 76 D150 got 15 sure it makes over double the HP but there a limit to mpg your gonna get and throwing $$ at ain't gonna change it plus sometimes it's more cost effective to pay the extra $$ at the pump.
 
jerry6 said:
So the transmission might have been one of the reasons for bad mpg . Makes sense , my 340 gets over 23 mpg on the highway , so you should be getting better than 15 mpg .My setup is 340 , 3:55 83/4 , 727 , with 235/60-14 tires out back . Makes 413 hp 398 torque .
Good luck hope the 360 gets better mpg , it should with a good transmission
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I find that very hard to believe, what kind of speeds do you hold on the highway? Also isn't a gallon in Canada larger than a gallon in the U.S. system?

I managed 18 MPG (American) tops on a long highway trip with my Duster, it has the engine in my sig which is very mild-mannered (maybe 325 HP tops) and also 2.76 gears in the back with a 904 trans which is more efficient than the 727 even...
 
well let me put it this way, I would cruise at 70 to 80 mph at 2500 rpm, and that's it, the car wouldn't go any faster than that and the engine won't rev any high than 2500 when in drive. So something with the engine and tranny is wrong.
Dropped it off at the shop today, Clark's Auto. The guy said that the timing chain could be worn out completely but we'll see, he's looking at it tomorrow.
 
MOPEkidD-3 said:
I find that very hard to believe, what kind of speeds do you hold on the highway? Also isn't a gallon in Canada larger than a gallon in the U.S. system?

I managed 18 MPG (American) tops on a long highway trip with my Duster, it has the engine in my sig which is very mild-mannered (maybe 325 HP tops) and also 2.76 gears in the back with a 904 trans which is more efficient than the 727 even...
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last time i checked a canadian "gallon" is one liter no??

anyways... i got 20mpg with my low 14 second slant six and almost in the 13's with it...
 
When we used gallons it was bigger something like 4.5 liters per gallon vs American gallon 3.8 liters but anytime I figure my mileage I use the American gallon.
 
MOPEkidD-3 said:
I find that very hard to believe, what kind of speeds do you hold on the highway? Also isn't a gallon in Canada larger than a gallon in the U.S. system?

I managed 18 MPG (American) tops on a long highway trip with my Duster, it has the engine in my sig which is very mild-mannered (maybe 325 HP tops) and also 2.76 gears in the back with a 904 trans which is more efficient than the 727 even...
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I keep it at a steady 3200 rpm or about 67-68 mph , all I really do is highway . live in the country so very little city driving .
 
jerry6 said:
I keep it at a steady 3200 rpm or about 67-68 mph , all I really do is highway . live in the country so very little city driving .
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I guess that makes sense, is the land flat where you live? I live near the mountains so there are big hills everywhere you go especially when traveling west.
 
MOPEkidD-3 said:
I guess that makes sense, is the land flat where you live? I live near the mountains so there are big hills everywhere you go especially when traveling west.
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There are hills , but compared to Denver they are mole hills , most are 800-1300 feet so nothing much .Most the highway I drive on is flat , not much elevation change , so that could be the difference . 45 miles into town , 5-10 miles city driving , then back on the highway . If I were to do lots of city driving I would look seriously into getting a G V overdrive , or a modern 6 speed auto . 6 speed with 4:11 in the 83/4 would help city mpg a lot .

Think the most $ I ever put in the tank was $58.00 , so 58 /1.38 =42 litres 42/3.76 =11.2 gallons . last trip was 178 miles and i put 46.00 46/1.38 = 33.3 litres or 8.9 gallons US or 7.33 IMP gallons which equals 20 mpg US or 24 Canadian .
Any how this car gets better mpg than all my other cars on the highway

Conversion for gallon to litre US 3.76 litres / gallon IMP 4.55 litres /gallon
 
7dswinger said:
well let me put it this way, I would cruise at 70 to 80 mph at 2500 rpm, and that's it, the car wouldn't go any faster than that and the engine won't rev any high than 2500 when in drive. So something with the engine and tranny is wrong.
Dropped it off at the shop today, Clark's Auto. The guy said that the timing chain could be worn out completely but we'll see, he's looking at it tomorrow.
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If it is the stock chain/ gear with the plastic teeth , yeah it could be worn . Back in the day I changed those things every 70,000 miles , they sure didn't last if you drove the car hard . Went through 3 on my dart in the 70's before i got smart and put on the set up from a 340 , never had a timing chain problem after that
 
well hopefully the shop will figure that out, their going to look at that. They showed me a chevy truck with a 454 with a timing chain on it you could basically take off with your hands it was stretched out so much haha
 
Ok so I got word back from the shop. He's going to have to fabricate a bracket for the throttle body for the kick down linkage which isn't a big problem, what is, is that the timing chain was loose, there's was apparently about 12 degrees of slip on ATDC and BTDC , so 24 total.....so it's getting a new timing chain. Said I should have it back Saturday, we'll see how it runs!
 
If you can make sure it's at least a timing set with steel gears (not plastic), preferably double-roller.
 
72 Valiant,245/60/15s,3.55 Trac Loc out back.727,tight 9.5 ger converter.mild 360.750 d.p,RPM performer.915 castings milled.080,stock re-ringed short block.GOOD valve job,bowl&throat work.Cam,Crower 269/282 advertised,112 l/c 223/[email protected] 13.20s,with wheelspin,before I got it.Went South on 101,to 405.Used a vac guage,kept speed at 62 to 64 mph.Was rewarded with 22 to 23 mpg.Matter of tuning,and knowing your combo.
 
MOPEkidD-3 said:
If you can make sure it's at least a timing set with steel gears (not plastic), preferably double-roller.
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+1 , I don't know why , but my 318 back in the day ate those plastic toothed gears . Still have 3 of them mounted on the wall . You'll have to change the crank gear as well , but it is worth it , at least in my opinion , unless they make better plastic gears these days . All i know is after switching to the double roller never had to play with timing chains again
 
Sounds good I'll let the guy know to install a double roller, shouldn't be too much more expensive than what it will be currently.
 
Went to the shop to see how it's going and it turns out he was going to install a double roller in the first place, so no problems. Only that summit sent him a set for a big block chevy, not a small block mopar so instead of getting my car back saturday I'll be getting it back Tuesday possibly next week.....oh well patients is a must now
 
x3 on the double roller, i got mine from comp cams, pre stretched chain and new crank and cam sprockets which can be indexed to advance/retard cam degree in 4 degree increments def worth the few extra bucks IMO
 
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