Dodgeboy
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Timing is set @ 18° intial with total 39°. Mechanical dizzy. Jacobs electronic ignition system
Let's Talk Miles per Gallon (Or Gallons per Mile)!
- Thread starter wedg2go
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Dodgeboy
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I'm hoping to get closer to 10mpg once the 850 holley is tuned.
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DetMatt1
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That seems like a lot of carb, no?
Comp solid Duane Porter design, 580ish lift and 244-248@.050 114 LSA
Dodgeboy
Well-Known Member
The Cam calls for a 800-850cfm carb. Orginally the shop got me a demon 850 (back in 2000) but the carb had defects so they used the "shop 750dp" to dyno the 383. Final carb jetting was 82 square with no pv (no vacuum @ idle). Then they got me a new 750dp, labelled the box 82 square, and sent me on my way. Years later i realized they had set the valve lash wrong and now i have 5" vacuum @ idle and a huge traction issue (lol). Peak hp (417hp) @ 5700rpm with wrong valve lash. The cam should be good up to 6800rpm and i wanna rev it up there. I've seen lots of similiar engine combos and i'm convinced my 383 has more hp in there somewhere. Hoping the bigger carb will help me find them. I still have the 750 incase the 850 proves to be too big. Also when i pulled the 750 apart to clean it I noticed it had the factory jets in it, but i'll try the 850 before i re-tune the 750
Cudafor36
Well-Known Member
My "old" motor the 340 with a 450 lift/duration cam, ported J heads, and a comp series 650 carb got 9-10mpg. Thats with a 727 tranny. Now I get 18.5mpg with my 392 and a silver sports four speed auto.
DetMatt1
Well-Known Member
I’m no expert but you may be giving up throttle response off the line in order to run 6800 rpm and why do you want to run 6800 rpm? Are you racing this car?
Dodgeboy
Well-Known Member
I've never been a fan of keeping the rpm's down. One of my reasons for getting a 383 was the fact that they can rev high (7000rpm) with just a valve spring change. Honestly I don't race the car but eventually I would like too.
Quick story.
My eailier mentioning six miles per gallon finds me at the pump quite often. Which is really not a big thing, but is interesting. Every now and then I will be met with a kind comment of "Nice Car" and of course it turns into a short friendly conversation while hogging the pumps (nobody has complained yet). I enjoy this time, even if it cost me 30 something a pop. I also enjoy leaving the station giving a little show and lightly "Running through the Gears" knowing they're watching. It my only time, it seems, that I ever have that opportunity to crack open the outboards since coming to a complete stop is a rare event around here.
My eailier mentioning six miles per gallon finds me at the pump quite often. Which is really not a big thing, but is interesting. Every now and then I will be met with a kind comment of "Nice Car" and of course it turns into a short friendly conversation while hogging the pumps (nobody has complained yet). I enjoy this time, even if it cost me 30 something a pop. I also enjoy leaving the station giving a little show and lightly "Running through the Gears" knowing they're watching. It my only time, it seems, that I ever have that opportunity to crack open the outboards since coming to a complete stop is a rare event around here.
Mopars & Missiles
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Hook up your vacuum advance so you have about 55* total at cruise, I think you'll gain a little mpg doing that. Not much, but some and every little bit helps! 
432 (383 block), Stealth heads, Lunati 703 (224/230), 3.55s, Sniper EFI, vac adv at about 44... last long trip I was holding it to 60-65mph, nice day, cool air, back roads, little traffic, not in a big hurry, and it shocked me silly with 19mpg on a 250 mile leg.
I think it's a fat pig
please post 8 spark plugs pics and specify the six pak set up...jetting, plates, timing, fuel levels, plug wires, coil, ignition box, thermostat temp, coolant mix, operating temp, radiator cap, lubricants in trans and rear end
Cuda Hunter
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Have not seen you around @wedg2go Not here or locally. Still around?
Still here, Cuda Hunter. Hope all is well with you. 2020 & 2021 found me hiding out from doing anything car related (shows). Even getting out and going somewhere had me closer to home. 22 & 23 did a few car related events in nearby towns. 24 had us all over the map traveling. Including Alaska. So little time for having anything to do with the Challenger until late last summer, while out for a drive and it stalled leaving me stranded near the hospital for 5 hours. Once again I contemplated the trouble I had with this ride. So I devised a three step plan to hopefully solve this stalling issue. I finished the first step about a month ago and it already has made a huge difference (running an aluminum radiator so it is running cooler). My next is to go back and rejet the carbs to run fatter and not as lean as I have them now. A richer mixture will mean a little cooler yet. Not much cooler but some. The last is a electric fuel pump, but finding a "continuous duty" pump leaves me a little leary over this fix so far. The summer of 25 will once again find me jet setting all over the world. But this time I am filling in the spaces with a few car shows when we're here (like the one at Perkins).
BTW - At the start of this tread, I was complaining about mpg. I discovered my inboard carb had a 6.5hg power valve. My vacuum is around 4hg - 5hg. Yeah! You can only imagine the fuel pouring thru that inboard carb and how messed up those plugs were. Now running a 2.5hg and mpg improved tremendously.
Mopars & Missiles
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Just on the off chance you haven't done it yet..........exhaust crossover is blocked off? Yes?
Unknown at this time. I'll need to check the build docs since I purchased the car only being told that the engine was "professionally built" But you're right. Definitely worth looking into. Thanks!
6PKRTSE
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Mine actually might be gallons per mile. Actually, it's not as bad as one would think.
Cuda Hunter
Well-Known Member
@wedg2go Glad to hear you are getting the issues sorted out and still around.
Next time you are stuck for 5 hours, give a call, or a text as you know how the phones are up here. I'd be glad to lend a hand if I can.
Had not seen your car around for a while.
Traveling the world is a great reason to not ride around the local area.
Question, as you are galivanting around, does any other place appeal to the eye as much as this county?
Next time you are stuck for 5 hours, give a call, or a text as you know how the phones are up here. I'd be glad to lend a hand if I can.
Had not seen your car around for a while.
Traveling the world is a great reason to not ride around the local area.
Question, as you are galivanting around, does any other place appeal to the eye as much as this county?
Xcudame
Well-Known Member
Just had to reply to this thread. 70 Challenger 383, factory 383/440 HP cam and 850 CFM Thermoquad. 15 mpg with my lead foot. 22+ mpg if I drive miserly!
Years ago, a friend of mine working for a dealership tweaked a 383 C-Body for a high mileage commercial and got close to 30 mpg. He went so far as removing the grease from the wheel bearings and splashing them with light weight oil. Leaned out the carb until it was slightly pinging at certain rpms. Removed everything from the trunk including jack and spare tire and trunk mat. All kinds of tricks to increase mileage that I can't remember. Needless to say, you couldn't drive it for long like that, but it made an interesting story especially during the fake gas crunch of the 70s.
Years ago, a friend of mine working for a dealership tweaked a 383 C-Body for a high mileage commercial and got close to 30 mpg. He went so far as removing the grease from the wheel bearings and splashing them with light weight oil. Leaned out the carb until it was slightly pinging at certain rpms. Removed everything from the trunk including jack and spare tire and trunk mat. All kinds of tricks to increase mileage that I can't remember. Needless to say, you couldn't drive it for long like that, but it made an interesting story especially during the fake gas crunch of the 70s.
It was amazing how many people stopped and asked if I needed help. I wasn't really blocking the flow of traffic, but there were quite a few kind hearted people that stopped their rides right in the middle of the road to see if I was ok. All I remember at the time, is in the back of my mind, I was chewing nails and the ignition modulator had given up. No reason, for that short of a drive, for it to crap out the way it did. Funny thing is a few minutes before the flatbed showed up, it started. Still had it towed home and I really believe the tow truck driver was a little thrilled. LOL! Not everyday one picks up a classic ride.
To answer your question my wife and I are here, in Salida, to stay. We always talked about our future about what we would do if one of us went first. Her, she might move back to Phoenix, buy a little condo, and set the ac down to 50 during the summer. Me? I always wanted to grow my hair long, buy a custom Dodge van, set out for Hudson Bay, and wrestle a polar bear. Seriously though, both her and I really enjoy Colorado. It's a great starting point to go see the rest of this nation!
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