Best magnum MPG?

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My wife's 2001 Durango (5.9-4x4) averaged 13.5 mpg whether it was driven up hill, downhill, pulling our trailer, or not. It was consistent, but not good for gas mileage. My 99 Dakota exented cab (5.2-4x4) has a best of 15 mpg in town. Both vehicles have 3.55 gears in the rear.
 
75slant6 said:
So in my 72 Duster with a 3.23 rearend, 1406 edlebrock and an overdrive 5 speed I should easily hit 20+? I'm hoping for 25+ on the highway but 20+ would be great too!
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Tune that carb right and you will see that easily especially with a 5 speed.
Edelbrocks can be tuned for decent mileage. I used an AFR gauge with mine.
I'm using a more advanced version of your 1406 (#1806 650 AVS)
I get 17 mpg on the freeway with my Duster but it has a non-LU A999 auto. (I get about 13-14 around town)
BE EASY on the secondaries.

Get froggy on the throttle and you'll see the mileage drop like a bad date.

I'm currently rebuilding a thermoquad, would be very interesting to see the difference once I'm done and tuned with it.

*Edit* PS: Make sure you use a clutch radiator fan not a solid mount flex fan. (Or maybe a good electric one if your inclined to do so).
 
By all means report back what the difference is once you get the TQ put on! I was thinking about getting a TQ for mine but I've been told there's a learning curve with those and since I'm new to carbs I figure I better get the edlebrock figured out first! Might end up swapping the factory injection on sometime or run a FiTech throttle body.
 
Chevy guys hate thermoquads what the hell would we want one of those for? Just curious....
 
Punisher66j said:
Chevy guys hate thermoquads what the hell would we want one of those for? Just curious....
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Well:
1. Its a spreadbore.
2. Its one of the most misunderstood carburetor. Each person I come across who knows how to work these things have stated that they are the ultimate street carb.
3. They reported to have better mileage than Edelbrocks and Holleys.
4. A lot of Chevy fanatics are clueless about the TQ's, there are a few that know what they're doing especially with their Rochesters and such.
5. Just imagine a 800 CFM carb that can be tuned to run on a mild small block.
And 6. The growl it makes as you hit the secondaries is priceless!.
 
Yep- tiny primaries and huge secondaries.

Ba-Waaaaaaaaaaaaooop.

Biggest pain I have is that almost all of the adjustment instructions start with-

Remove carb from engine and turn upside down...
 
A quadrajet is 10x the carb of a thermoturd and not made of plastic. They will get better than a 1406 but still a carb. Put the FI back on and you will get much better mpg. As far as all the Dakota/Durango talk, bet most of you are still running crap plugs gaped at .035". Upgrading ignition like our upgrade kit will typically result in 2-3 mpg and run much better.

What a Dak or Dur will pull on road has no comparison with an A body, they weigh 1500# more , are 4wd which sucks power and the hood is taller than the roof of A body. While an A body is no Triumph TR-7 wedge, it is much closer than the Dodge truck profiles which are pretty much a sheet of plywood at speed. That will make a huge diff in wind drag which is what kills mpg.

Like I stated earlier, I actually have checked mpg in a 71 Swinger with 5.2 Mag FI and OD AT, it got 25 on hwy cruising at 75+. close to 20 in town. It got 18 in Dak with AT on hwy, I know this because it was a buddys truck and when it got clipped by red light runner, I bought it from insurance co. 18 to 25 is a 30% improvement just from swapping bodys....
 
magnummopar said:
A quadrajet is 10x the carb of a thermoturd and not made of plastic. They will get better than a 1406 but still a carb. Put the FI back on and you will get much better mpg. As far as all the Dakota/Durango talk, bet most of you are still running crap plugs gaped at .035". Upgrading ignition like our upgrade kit will typically result in 2-3 mpg and run much better.

What a Dak or Dur will pull on road has no comparison with an A body, they weigh 1500# more , are 4wd which sucks power and the hood is taller than the roof of A body. While an A body is no Triumph TR-7 wedge, it is much closer than the Dodge truck profiles which are pretty much a sheet of plywood at speed. That will make a huge diff in wind drag which is what kills mpg.

Like I stated earlier, I actually have checked mpg in a 71 Swinger with 5.2 Mag FI and OD AT, it got 25 on hwy cruising at 75+. close to 20 in town. It got 18 in Dak with AT on hwy, I know this because it was a buddys truck and when it got clipped by red light runner, I bought it from insurance co. 18 to 25 is a 30% improvement just from swapping bodys....
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*Yawn* Here we go again...
I have talked to numerous people and have actually seen the results of a properly tuned Thermoquad. Sorry I'm basing off of what I've SEEN vs. ones OPINION. The only reason people have problems with the plastic body of the TQ's is because of heat from the lean burn emissions era. But that doesn't apply to cars that are modified and tuned to not run lean. I've used Rochester Quadrajets before OK carb if built and tuned right they are very comparable to TQ's.
 
Actually, the biggest problems with a thermoturd is that the base plates warp and suck un metered air past throttle plates. This is my"opinion" after building carbs since 1984, but what would I know about building or tuning carbs, I have probably only built as many carbs as you have owned pairs of socks. You can put a thermoturd on your birthday cake if you want, its doesnt make it any less of a POS than it is. I would not put a square wheel on my wheelbarrow just because guy down the street did, they are round for a reason. like comparing a musket to an ar-15....yawn. BTW FITech is well under $1000 so no excuses for carb made by Mattel.

Back to OT, if you want great MPG out of your magnum, dump the monkey with a bucket of gas dispenser and join the rest of us in the 21st century with multi port FI, otherwise suffer the fate of mi teens MPG.
 
Been building carbs since the 70's. Thermoquad is a Great carb if you understand how carbs work. Q-Jet is as well. Problem is too many that don't know,fool with em and turn em into junk. TQ needs an insulating gasket and no more base warpage.. Which wasn't that common until later years as temps climbed or a hot climate. Q-jet is a little better and stingier with its metering.It uses n insulating gasket,But the wrong one for your application can cause idling problems. Also small fuel bowl makes it hard to feed a good running bigblock. it can be done,but needs a BIG needle and seat. TQ,Passes more gas,,Dual bowl and .110 seats work well. The new Street Demon is a good attempt at a TQ copy,But only 650 cfm. Better and more durable bowl design.
 
Cars weight and aerodynamics will be the ultimate limit to gas mileage and engines efficiency plays a big part but the engines we deal with have similar efficiency.

Which leave hp and engine size. I like to think of engine size dynamically instead of its static size 318/340/360 etc... dynamically an engine size is (rpm/2 ) × cid but the actually size don't matter so much so I just compare by multiplying rpm or gear size to cid and divide by the cid I want to compare to. Eg if you want a 360 to have similar mileage as a 3.23 geared 273 you'd just times 273 and 3.23 and divide by 360 which would equal 2.45. So a 360 would need 2.45 gears to get similar mileage to the 273 but would also have similar performance from the lost in torque from the higher gear ratio.
 
magnummopar said:
Actually, the biggest problems with a thermoturd is that the base plates warp and suck un metered air past throttle plates. This is my"opinion" after building carbs since 1984, but what would I know about building or tuning carbs, I have probably only built as many carbs as you have owned pairs of socks. You can put a thermoturd on your birthday cake if you want, its doesnt make it any less of a POS than it is. I would not put a square wheel on my wheelbarrow just because guy down the street did, they are round for a reason. like comparing a musket to an ar-15....yawn. BTW FITech is well under $1000 so no excuses for carb made by Mattel.

Back to OT, if you want great MPG out of your magnum, dump the monkey with a bucket of gas dispenser and join the rest of us in the 21st century with multi port FI, otherwise suffer the fate of mi teens MPG.
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I dunno I can rebuild a core for Around $100 which is a heck of lot better than "under $1000" plus it's simple to use. FI doesn't magically get you 5-10 mpg over a well tuned carb. I've seen plenty of well tuned carbs get well over 20 mpg. Its called overdrive, gear ratio and proper AFR. I guarantee he can get over 20 With THAT overdrive transmission. Do you know my age? Do you know me? Do you know what I have or have not done? Did you know that I was a mechanic for a $120000 engine for a 45 million dollar piece of military hardware? No I guess not, you just "assumed" that I'm an inexperienced kid. But I guess some of these folks on this forum or the older guys (my father included) who have been teaching me don't know Jack because you know they were tuning carbs before you even owned a car. But hey what do I or they know?... I'm done with you. You can keyboard commando all you want. You'll be on my ignore list soon enough.
 
Punisher66j said:
So you guys would run a thermaquad over a 650 edelbrock?
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Yes and no. 650 AVS is a very good carb. Easy to tune and great aftermarket support. I've tuned mine to get around 17 mpg. Which is pretty damn good considering the fact that I have 3.55 rear ratio, 3 speed automatic (non-lockup) and an airgap manifold.

17 mpg at 70 mph at 3200 rpm's at 4500 ft altitude. I'm happy. If was to get an overdrive setup I'll easily hit the 20 mpg mark. (Despite what some people think)

The thermoquads I've seen on some of the local power wagons and A-B-E body's here in the local mopar club i'm in has me convinced.
The only problem is getting aftermarket parts. but usually solve that problem by buying cores that occasionally show up for 30-50 bucks a pop.
 
Tantibus-74 said:
I dunno I can rebuild a core for Around $100 which is a heck of lot better than "under $1000" plus it's simple to use. FI doesn't magically get you 5-10 mpg over a well tuned carb. I've seen plenty of well tuned carbs get well over 20 mpg. Its called overdrive, gear ratio and proper AFR. I guarantee he can get over 20 With THAT overdrive transmission. Do you know my age? Do you know me? Do you know what I have or have not done? Did you know that I was a mechanic for a $120000 engine for a 45 million dollar piece of military hardware? No I guess not, you just "assumed" that I'm an inexperienced kid. But I guess some of these folks on this forum or the older guys (my father included) who have been teaching me don't know Jack because you know they were tuning carbs before you even owned a car. But hey what do I or they know?... I'm done with you. You can keyboard commando all you want. You'll be on my ignore list soon enough.
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I can buy a black and white TV for $100 too, but I am not giving up my 60" LCD. You called me out then got pissy...and what does working on some army junk have to do with what MPG a magnum gets? Did your 45 million dollar hardware have a thermoquad on it, or even 30 year old bad technology on it or was it state of the art modern technology? If you work on 45 million equipment, why wouldnt have more than $100 for a fuel system? You dont even have a magnum in your car so why jump in just to wave your thermoquad flag?

Oh, and you guarantee that he can get 20 with THAT OD trans but suggest a thermoquad for it? FYI, the RE series of electronically controlled trans REQUIRES a pcm from a magnum with FI to run it. You will never get the same MPG with your carb, regardless of what trans you run. kids these days :banghead::banghead::banghead:
 
magnummopar said:
I can buy a black and white TV for $100 too, but I am not giving up my 60" LCD. You called me out then got pissy...and what does working on some army junk have to do with what MPG a magnum gets? Did your 45 million dollar hardware have a thermoquad on it, or even 30 year old bad technology on it or was it state of the art modern technology? If you work on 45 million equipment, why wouldnt have more than $100 for a fuel system? You dont even have a magnum in your car so why jump in just to wave your thermoquad flag?

Oh, and you guarantee that he can get 20 with THAT OD trans but suggest a thermoquad for it? FYI, the RE series of electronically controlled trans REQUIRES a pcm from a magnum with FI to run it. You will never get the same MPG with your carb, regardless of what trans you run. kids these days :banghead::banghead::banghead:
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And yes to answer your immature question the Aircraft was built from the late 60's. And the turbine jet motors were built from the 80's. The reason I brought that up is make sure you know that I'm no rookie to mechanical work since you're fluffing yourself up with "Hey I've been rebuilding carbs since 1984" Well good for you but yet you assume that I'm just a kid that doesn't know anything.

They already tested it, there is only a 1 maybe 2-3 mpg difference in a well tuned carb vs. Fuel injection. The biggest difference in mpg's is again LET MAKE MYSELF CLEAR is the gear ratio. But clearly you don't even know to how work on carbs because it ain't that freakin hard. I pulled apart and reverse engineered many carbs. I know exactly how they work but you obviously must have difficulty with em.

So on your previous rant on how you can never get more then mid teens mpg just proves my point. And here your saying you don't believe he can get 20 mpgs with an OD? When I can get 17, 17 mpgs with no OD, with an AVS!! Oh the horror, the humanity! Wow something must be wrong, I must have done something wrong, oh wait I know I'm just a kid that doesn't know anything. By the way do you know how old I am? I'm still waiting for your answer?

No... Your just spouting off ignorant statements and blatantly insulting my intelligence. You clearly "ASSUMED" I'm just a kid that knows nothing. Yeah real mature there.
Who's getting pissy? You're the one that started throwing insults. I did not throw any insults at you until you started making condescending comments by trying to talk like you are above me. Which you are not.

I'm done, you offer nothing constructive and you obviously have a history of riling people up. So yeah I'm done with you.

BTW. I'm probably more into the 21st century than you are. I was a jet engine mechanic. I'm now in Cyber Transport. Which means I'm basically an ethical hacker working for the military. Don't bother with a reply you're on the ignore list.
 
I am hopping, hopping that this thread can stay smooth :glasses7: I am not placing blame anywhere :coffee2:
But ! Lets keep it nice men, this is a good thread that I may have to clean up so others can enjoy the info here :color: ok.. Thank you :glasses7:

I do know that a bad worn out or badly set up rear end can suck the mpg out of any car/truck :D
 
273 said:
Cars weight and aerodynamics will be the ultimate limit to gas mileage and engines efficiency plays a big part but the engines we deal with have similar efficiency.
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I really don't think weight has much of a role. Lots of heavy cars get pretty decent fuel mileage while it's easy for older cars/small trucks to get worse mileage while being significantly lighter among other reasons to not consider weight much.

Tantibus-74 said:
Yes and no. 650 AVS is a very good carb. Easy to tune and great aftermarket support. I've tuned mine to get around 17 mpg. Which is pretty damn good considering the fact that I have 3.55 rear ratio, 3 speed automatic (non-lockup) and an airgap manifold.
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You know something funny? I figured that was your gear ratio- I was looking around for your post you mentioned your gears because that was my max on a car with 3.55s.

I really don't like to touch anything related to a Carter carb. My experience with them hasn't been better- maybe I can't be bothered to tune them properly. Even though I got around 25mpg with my car tuned well, I could never be bothered to tune my truck's Holley better. It started adequately year-round including in the freezing weather and did great- fuel mileage wasn't horrendous but almost definitely could have improved. (like 9.8 loaded, 12.9 empty) I'm a big fan of simple- just set the choke appropriately according to the factory instructions and start it, then warm it up under way.
 
My old 73 dodge would get 17 consistently at 70 pulling a trailer. 360 two barrel and 3.23 gears. Hoping to drop in the stock 5.2 magnum and pull down 21 at 70. But I am gonna hop up the cam after I've got the cash the 5.2 in my dodge dakota would never get more than 15 mpg. I tried to granny it on the highway and it still got 15 mpg. So I floored it everywhere. Always got 15. Nothing more or less.
 
Infecteddog said:
I really don't think weight has much of a role. Lots of heavy cars get pretty decent fuel mileage while it's easy for older cars/small trucks to get worse mileage while being significantly lighter among other reasons to not consider weight much.
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More weight is more effort and more effort is more fuel consumption. It easy to move an empty wheel barrel around all day compared to one full of dirt. But I'm sure your body will consume more fuel doing it same as your car. Every hundred pounds you drop off your car is something like a gain of 10 hp and an engines hp is directly related to the amount of fuel it burns.
 
273 said:
More weight is more effort and more effort is more fuel consumption. It easy to move an empty wheel barrel around all day compared to one full of dirt. But I'm sure your body will consume more fuel doing it same as your car. Every hundred pounds you drop off your car is something like a gain of 10 hp and an engines hp is directly related to the amount of fuel it burns.
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Do you lose .5-1mpg when you bring the family on a road trip compared to driving by yourself? Extra weight, more effort, more fuel consumption- but in practical application it doesn't act that way. I have never personally observed that kind of a change, I've always seen it relatively the same in similar weight brackets despite 100-600 lbs difference.
 
Factory manufacturers have spent millions of dollars trying to get any advantage when it comes to mpg. They spend millions of $ and tons of time in wind tunnels making bodies more aerodynamic so you get better mpg. If vehicle weight made a huge difference, they would spend more time on a scale and less time in the tunnel....its all about aerodynamics, much more than weight. The weight factor comes in when you are talking about puny engine like aprius that simply cant push more than 2500#s. In a V8 with lots of torque, its the profile of the body lines that matter most.
 
Infecteddog said:
Do you lose .5-1mpg when you bring the family on a road trip compared to driving by yourself? Extra weight, more effort, more fuel consumption- but in practical application it doesn't act that way. I have never personally observed that kind of a change, I've always seen it relatively the same in similar weight brackets despite 100-600 lbs difference.
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I agree real world gains are small that's why it's not worth spending too much money on improving fuel mileage it's hard to recoup the cost. But weight does make a difference especially intown driving. The resson gains aren't huge cause for huge gains percentage wise is actually small in actually mpg numbers.

My 5.9 jeep gets 12.5 mpg average. I would imagine it would at least get 15 mpg in my cuda that's a 20% increase but actually equals to a 2.5 mpg increase and that's a 1500 pound difference.

All I was trying to say is it takes a certain amount of hp (fuel) to move a certain weight and aerodynamics that's why I said ultimately. Over 20 mpg in town would be hard and expensive.
 
magnummopar said:
Factory manufacturers have spent millions of dollars trying to get any advantage when it comes to mpg. They spend millions of $ and tons of time in wind tunnels making bodies more aerodynamic so you get better mpg. If vehicle weight made a huge difference, they would spend more time on a scale and less time in the tunnel....its all about aerodynamics, much more than weight. The weight factor comes in when you are talking about puny engine like aprius that simply cant push more than 2500#s. In a V8 with lots of torque, its the profile of the body lines that matter most.
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Weight reduction is hard to come by and is expensive
It's hard to beat the cost and durability of steel, mid and full size cars are always gonna be heavy.
 
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