Newbie with 454 sucks 6 mpg

[chumstone]

Great site! I've had this 73 Chevy now for the last 7 years and every chevy truck I've owned has made me a chevy man.
OK the truck is a Camper special, and had 60k when I got it from an old guy who ordered it new. He said that it got 12 mpg when it was new, I got 11mpg highway, 9 mpg city. Well the thing started to smoke and I decided to get another engine. I did not know what I was getting into at the time, but I found a rebuilt 1985, 454, bored .30 over, precision balanced engine, and has 10 to 1 flattop pistons, RV cam, 1991 motorhome heads, double roller timing set, high volume oil pump, Edlebrock intake manifold, pertronix HEI and Edlebrock 1411 750 cfm carb. Single 3" exhaust and chrome carb aircleaner, paper element. Also Turbo 400, 2x4, 3.73 gears with utility body and truck weighs 8700. I'll add signature later.
The engine has lots of power and pulls real hard! Driving less than 1000 miles a year because of the low mpg. Anybody got any ideas to improve fuel economy? Should I have installed a small block 350? Anything that a couple of hundred would do to get 2 more mpg?

[isenegger]

a real good ignition system... good plugs, high output coil and at least 8mm of bigger wires. u should do ok with the bbc. no need for the sbc. you would have to push the sbc harder to do what the bbc does. oh and what size tires do u have?

[68GMC454]

my 84 3/4 454 gets 6,, i know it needs work, but im geared lower to. but i drive it everday, when i drive. at the wieght you got, i wouldnt expect to much more out of it..i would be happy if i could get 10,,lol...make sure carb and timeing are right to,, my timeing is off i know that, but it needs new chain to be set for up here where i live..do good tune up on it, make sure air filter is clean...tire inflation is right..

[see ten]

Remove your engine driven fan and replace it with an electric setup. I did this to both my 72s and our Jeep (my Nissan came that way).

[Restrorob]

I've have a Ram 250 conversion van with a 318 that only gets 10 mpg at best with a fresh tune and carb. o-haul .....Good Luck with your gas hog !

Originally Posted by see ten

Remove your engine driven fan and replace it with an electric setup.

Did you record your MPG difference performing this fan swap ? I have a electric fan kit I bought for my truck project below but may just install it on my van for now. That's if the MPG difference is noticeable.



Looks like maybe your radiator may not be long to check out on you !
Check this place out; http://www.radiatorbarn.com/ I have bought two from them so far with no problems.

[jeffspower]

I'd read the spark plugs to determine if the carb is rich or lean. Either will cause poor MPG. Edelbrock carbs aren't a very good MPG carb, & are usually jetted a little rich so they will run fair out of the box on most stock to mild engines of any brand. Every engine needs jetted & calibrated differently. It could have too stiff of power valve springs, causing a rich mixture at low engine load. Specs on the springs & a vaccum gauge to determine your manifold vac. running down the road is where to start. Then play with jetting to get your plugs to show a very light brown around the edge of the porcelin. Or, better yet, put in a oxygen sensor & you can read what it's doing going down the road with a digital voltmeter.

If all checks out there, look at your timing curve. See what advance reading you get at cruising speed.

Better MPG might not take much money, just a bunch of time tuning. Do you still have the OE Q-jet? If it's in good shape- might be the best way to go. A decent tuned Q-jet will usually do better MPG than the best tuned Edelbrock.

[Donnylee]

My Buddys 85 Dually gets about 9MPG. Roughly 12 on the freeway. Its about the same as the 91 Dually I had with TBI. Bottom line is 454s are plain thirsty. What you can do is make sure your jet/rods are not overtly to fat, and your running optimum total timing. To much retard, and they become thirsty pigs.

I also agree Edelbrock carbs are always seeming to be over jetted in my experience. Jeff makes alot of good points, tune, tune, tune..... A good running tuned engine will be efficient. But on that same note efficient and 454 do not go together very well..... Good luck!

[boatpuller]

that's the world of big blocks.they weren't designed for gas milage as i'm sure your aware of.but....they will put a smile on your face. (except at the pump)