Mpg on a mild 360?

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doogievlg

doogievlg

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So I'm kicking around the idea of driving my dart to the nats for the first time. It's about a 200 mile trip and I'm trying to figure out the gas budget. I honestly have no clue what mileage I am getting because I usually am just on back roads with the pedal to the floor. I'm trying to get a estimate on highway mpg though. My combo is:

360 .30 over
Eddie heads
Mp. .484 cam
Performer rpm intake
Hooker headers
727 with 3000 rpm stall
3:55 gears

I was thinking using my Eddie avs 650 would help but I also have a Holley 750 dp.

I'm sure I'm not the only one with this combo or a similiar one so what are others getting for mpg?
 
Just a guess....15 if you keep it around 60mph. Glad to hear you're driving your car there. Someday I will. Have a safe trip and I may see you there. tmm
 
I'm just kicking around the idea. I drive the car a ton just never on the highway so I am nervous to say the least.
 
Well, It won't be good. Your rear gear may be the biggest hindrance. I have a 72 Duster with a mild 360; it has a performer intake and eddie 750 CFM carb, factory ignition at 10 degrees BTDC and also has vacuum advance, iron 587 heads, hedman shorty headers, and a comp flat tappet 268 cam. My duster is a 727 auto with 3.90 gears in its 8-1/4 rear. I recently took it to Crown Point IN to join the Hot Rod Power Tour for 1 stop, and I had to get in behind a semi and go 65 mph because my gears had the engine at 3400 rpm. Yes it needs overdrive. I did 15.3 mpg on the way up, but significantly worse on the way home as I had much more passing and less semis to cruise behind. My personal experience is 1. Edelbrock carbs are reliable but not especially fuel thrifty, and 2. Double pumper carbs make more power, are less reliable, and significantly worse on fuel economy. If it was up to me to budget mpg, I would assume 12-13 as a worst case.
 
4 _6mpgs with 456s...highway...8-10 city driving lol
 
That .484 Purple's overlap ,doesn't help. The 750 double pumper works fine,don't tip into the secondaries. Run a vacuum gauge,keep it 62-65 m.p h.. The converter, is the" if" here. My advice: run the double pumper,don't whack it down. With today's pump gas,most vacuum secondaries need tuning time,on the primaries. (I.m.o....750 double pumper-15-17 m.p.g.).
 
Hell, my stock 318 in my '77 D100 only gets about 11mpg! I'd be happy with 15mpg out of a warmed over 360!
 
Hey guys, he has 3:55's. What size tire and what's your rpm @60 mph?
 
toolmanmike said:
Hey guys, he has 3:55's. What size tire and what's your rpm @60 mph?
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This was my question.
Run a test. Fuel up run it on the highway for a half of tank. Then refuel and do the math. Real numbers is the way to go.
 
Well, it is what it is. If you get 15 it will take 13+ gallons, if you get 12 you will spend a little more but only a couple gallons more.
 
I'll be doing 800 miles to the nats in my Jeep at 20 mpg. But I still think my bar tab will be more then gas.
 
My 71 got between 18-21 if I drove it gently. It was a very mild 360 with a TQ, 904 and 3.23s with 275 60s on the rear. It would run 13.90s like it sat, or I could swap in the 4.10s and slicks and it would go 13.60s. Had the Crane magic cam in it.
 
I did about a 1300 mile round trip in my 70 Duster a couple of years ago, and got about 14.5 mpg. That was with a #587 head 360, about 9.5:1 compression, stock 340 cam, cast intake, Edelbrock 600 carb, and 340 exhaust manifolds. Also an A904, and some 2.94 gears specifically for the trip. That's with two 250+ lb guys and a weeks worth of gear onboard. We did a LOT of 80 mph, and looking back, it's more like we were trying for tickets, rather than economy...
 
WRB426 said:
This was my question.
Run a test. Fuel up run it on the highway for a half of tank. Then refuel and do the math. Real numbers is the way to go.
Click to expand...

Like you said....fill it up, drive 50 miles or so and fill it again. Divide the miles traveled by the gallons used.... Bingo!. Your long trip mileage should increase by a slight bit if driven easily.
 
RustyRatRod said:
My 71 got between 18-21 if I drove it gently. It was a very mild 360 with a TQ, 904 and 3.23s with 275 60s on the rear. It would run 13.90s like it sat, or I could swap in the 4.10s and slicks and it would go 13.60s. Had the Crane magic cam in it.
Click to expand...

R.R.R.,wide lobe centers work,for street ability. Cut back on overlap ,work on actual headflow & compression. Watch life, get good.
 
................I don't think anybody mentioned...........

Are you running a vacuum advance, and how is the timing and curve set up?

What are your "gut feelings" on jetting? Is it fat? lean?
 
Honestly I'm not sure on jetting. The Eddie is out of the box and the Holley was sort of a gift.

Initial is at 15
Total is 35
 
doogievlg said:
So I'm kicking around the idea of driving my dart to the nats for the first time. It's about a 200 mile trip and I'm trying to figure out the gas budget. I honestly have no clue what mileage I am getting because I usually am just on back roads with the pedal to the floor. I'm trying to get a estimate on highway mpg though. My combo is:

360 .30 over
Eddie heads
Mp. .484 cam
Performer rpm intake
Hooker headers
727 with 3000 rpm stall
3:55 gears

I was thinking using my Eddie avs 650 would help but I also have a Holley 750 dp.

I'm sure I'm not the only one with this combo or a similiar one so what are others getting for mpg?
Click to expand...

My car isn't that far off from that, and i would average 10-12 on the highway. The convertor slip is murder. You'll be turning 3k at like 55mph.
 
It will depend on the tuning, the throttle, and the convertor. My impression is it won't be more than 10mpg if it's an older type "10 inch" 3K stall. Witha tighter unit (so cruise rpm is above the flash stall rating) then you will do much better assuming the carb and timing curves are spot on. I'd also be running the vacuum advance - without it you're giving up anywhere from 10-30% in mpg.
 
My 340 4 speed with an 850 TQ and 3.23 gears will get 15-18 going 70 mph on the freeway... Driving mine down from Grand Rapids MI so i have a 350 mi drive to get there... best part about the weekend is the drive there and back.
 
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