Driving the 426 Street Hemi - Thoughts

[INTMD8]

5 or 6 mpg?

About 9, so yes rather dismal. Still cheaper and more available than race fuel. (all iron and 12.4-1 compression).

4.10 gears and only a .82 overdrive doesn't really help.

 

[AR67GTX]

That’s actually a lot better than I would expect knowing the 85 fuels are known to lower mileage considerably.

 

[mrhemi]

I have owned and driven my '69 Charger R/T for 40 years. The Hemi has its need to be kept in tune for sure, but runs just like any other car from the era. Every 5000 miles I would complete the major tune up, including lashing the valves. Back when I drove mine to the NHOA meets and the Mopar Nationals, it would consistently return 18 MPG Canadian on the highway cruising at 80. That seemed to be the sweet spot as that was right at the point of the second carb coming in, but not quite. I run mine on 93 or 94 octane with a little 100LL or leaded race gas mixed in for the exhaust valves. Like others have pointed out, a bad running Hemi is just not tuned properly. Tuned "properly" is nothing special other than what is in the FSM.

 

[joe smith]

I have owned and driven my '69 Charger R/T for 40 years. The Hemi has its need to be kept in tune for sure, but runs just like any other car from the era. Every 5000 miles I would complete the major tune up, including lashing the valves. Back when I drove mine to the NHOA meets and the Mopar Nationals, it would consistently return 18 MPG Canadian on the highway cruising at 80. That seemed to be the sweet spot as that was right at the point of the second carb coming in, but not quite. I run mine on 93 or 94 octane with a little 100LL or leaded race gas mixed in for the exhaust valves. Like others have pointed out, a bad running Hemi is just not tuned properly. Tuned "properly" is nothing special other than what is in the FSM.

What rear end gears in your car?

 

[mrhemi]

3.54 Dana, 4spd. 18mpg Canadian is about 14.5mpg US.

 

[1969VAGTX]

All this talk about gas mileage, and I was just curious what fuel blend people are running. I am fine with running only premium unleaded if that will hold up okay. I have no need to run 87 or 89 octane. I can stomach the added fuel cost to run 93. I just wanted to get a sense of if that is doable. I gave up worrying about gas mileage when I bought my 8500 lb. Dodge Mega Cab that might as well have a fuel bladder in the bed of the truck to handle its mileage.

 

[Edward Zeliesko]

108/add good gas 50 -50 ?

 

[Hemirunner]

3.54 Dana, 4spd. 18mpg Canadian is about 14.5mpg US.

My 572 hemi averaged 13mpg on Dragweek in 2010 with a 3.73 rear gear. We were running anywhere from 45mph in the rain to 75mph on the back roads. Best NA hemi combo I’ve ever had, massive torque, drive anywhere, low 10 car on pump gas. Current combo will be tested in June on Midwest Drags.

 

[mrhemi]

All this talk about gas mileage, and I was just curious what fuel blend people are running. I am fine with running only premium unleaded if that will hold up okay. I have no need to run 87 or 89 octane. I can stomach the added fuel cost to run 93. I just wanted to get a sense of if that is doable. I gave up worrying about gas mileage when I bought my 8500 lb. Dodge Mega Cab that might as well have a fuel bladder in the bed of the truck to handle its mileage.

93 octane is fine for a street Hemi, especially if you can blend some leaded fuel in that will leave you with a lead content of .5 grams/gal. (protects the exhaust valve seats) For example: 1 part 100LL Av gas (2 grams/gal.) to 3 parts 93 pump gas will leave you with .5 grams/gal and give a slight octane boost above the 93. There are a couple of threads here discussing blending various leaded fuels still available.