I was asked on another page on the site to post this essay in the performance section. I hope it is useful and informative.

Specifications for the build of my 451” B block engine which delivers 25 MPG and pushes the 3975 lb Charger into the 11’s.
First of all, keep in mind that my mileage claim is for Imperial gallons, which we use in Canada. For US gallons (smaller by 20%), the number would be 20 MPG.
Another note is that I have had many years experience building Mopar hot rod engines and although I don’t have any magic, I do use a great attention to detail in machining and assembly.
I first built this engine in 1999, using a 400 block, 440 modified steel crank with reduced main journals, stock forged 440 rods highly prepped, 452 motorhome heads ported and polished with oversize valves and a Mopar 284º hydraulic cam. The intake was an old 383 Torker and the carb was a stock 1968 440 AVS Carter. After a couple of upgrades to an MP 284º solid lifter cam and a Six Pack set-up, I swapped the 727 transmission to a full manual shift 518 with lockup converter. This package got me into the mid 12’s and around 22 MPG.
After a few years and 30,000 miles of listening to the tappet clatter from the MP solid cam, I decided to go to a hydraulic roller cam and aluminum heads. After 40,000 miles of 7200 RPM shifts, I replaced the bearings, but left the rings and cylinder walls alone. Another reason for this upgrade is that I am running a 518 overdrive trans and most of the time the engine is below 2000 RPM, so I wanted much more bottom end torque and, believe me, this engine has it. Over 600 lb/ft from 2000 up to 4000 RPM.
Pretty much matches my Cummins diesel.

Here is the current engine I have now:
Compression ratio: 10.55:1
440 Source Stealth heads with mild port work, 84 cc chambers
Comp hydraulic roller cam, grind # XR274HR-10, Part # 23-710-9
Hughes Hydraulic roller lifters
Speed-Pro aluminum roller rockers (from 1999 build)
Smith Bros pushrods
Arias flat top forged pistons (custom from 1999 build)
440 Source fluid damper
Melling HV oil pump with ½” pickup and 7 qt pan (homebuilt) from 1999 build
Factory 440 Holley Six Pack carbs ( center carb jetted down to 62’s)
Edelbrock 383 style Six Pack intake
440 Source aluminum water pump and housing (modified)
The engine is all done at a little over 5000 RPM, so I use that as a shift point. It idles at 750 RPM in gear and gives 12+ inches of vacuum with a slightly rumpy idle. I have Hedman headers ceramic coated (from 1999) and a full 3” exhaust system front to back that I built myself. I use Dynomax mufflers and 3” glass packs as resonators in the tailpipes. The rear end gears are 3.91:1 Sure-Grip in an 8 ¾ housing. The car weighs 3975 with me in it at the track.
My little carb secret for mileage is simple. I put an electrically operated vacuum solenoid (minivan purge valve) in the vacuum signal line from the center carb to the outboards. I shut it off (no outboard carb action) for 99% of my driving and only use the outboards for the odd chebbie or phord that needs a lesson. I just recently dynoed another almost identical engine and we made 405 HP on the center carb only. This is lots for street use.
I use a Jacobs Ignition system from 2001, they don’t make them this good any more. Plugs are gapped at .055”. Champions, of course. I can run on 91 octane on the street, but use 94 at the track just to make sure there is no detonation, as I couldn’t hear it if there was. I run through the mufflers, but the noisy chebbies are pretty loud. If anyone has more questions about this set-up, please contact me through the site and I would be pleased to answer.

cool, the six-pack is the key. I get about 14-15mpg to and from the track (44 miles round trip). This is on backroads at an avg of about 50 or so.. It can be done. I however have 70's in mine.

I don't spend a lot of time on these forums because everyone has a different opinion or a different experience. This cam only has 7º of overlap and is a torque monster (read: truck puller). I have been at this game for over 50 years and one ride in this car will change your mind. I built it for the torque, not bragging rights.

did you run an ultra bell on the 518?

I could have used a few more MPG at drag week

The mileage numbers of 20 MPG isnt bad being that
your running a 2 bbl carb and a 518 with lock up and
overdrive... and I am sure this is highway mileage
to base the average on

I just finished up a 451" with a lunati hyd roller Mopar stage 6 heads mated to a 4L60 and am getting 17 MPG ( US gallons)
Using a quickfuel 850 carb, Dana 3:55 rear end
cam card.... http://www.lunatipower.com/CamSpec.aspx?p=60312

Power output? Don't know never dyno'ed it? 540 or so I'd guess? Engine builder figures closer to 600? Don't know , don't care. It's more motor than the tires can handle anyhow!
Just a street car, not a drag racer.
More info on the engine build... http://www.cuda-challenger.com/cc/index.php?topic=78386.0

I like my cake... and eating it too!

Yes I did. I have a full article written on the swap, do you want it?

I wouldn't use it on an engine that big. I just finished a 500 with the same specs exactly as my 451 and it made a little less HP & TQ. I think the next cam up in that series would work a little better. I think the 383 Six pack intake is too small, as well. When I put it on, I lost 1200 RPM on the top end from my old 383 Torker and an AVS.
However, if you're running a bigger intake, so it's not the choke point, I think the Stealth heads might be the next problem.
If you can get accurate flow data for your heads, Desktop Dyno will help with the cam and manifold choices. The actual dyno numbers were a little larger than the desktop numbers, by about 2 or 3 %. You have to ensure you're not trying to fool yourself with the computer program, it is accurate if you don't BS the input info.

Definitely highway cruising mileage. When I'm playing hard it's just the same as every other hot rod.

I was getting ready to scream BS just glancing through the specs 3.92 gears 451 inches 25 mpg, then I saw the 518 so it has more like a 2.70 final drive and then noticed the Canadian conversion thing and the 20 mpg American and thought it sounded like a really nice ride


Got to admit, after building similar engine for a while now, I am still a little suspicious of the 600 lbs at 2000 RPM though

Those are the @0.050" figures, overlap at advertised duration is 58*.

Impressive numbers. One thing I do not understand: The streetHemi with all the good parts inside made 490 in torque, the 440 magnum had 480, some GM 455 engines had around 500, this was SAE in the 70's (Which were known to be optimistic). Then this example is 20% more in dynoed torque, at almost the same swept volume and a tad more CR. Can it be correct? What have I missed? Are the Stealths like supercharging an engine? Do the 451 light weight pistons matter at 2000 rpms? Please explain, I am really interested in how this can be done, as a 523 stroker I built some years ago with 11,7:1, 590 cam, M1 intake + 1050, and ported St6 heads barely made 600 lbsft. I am building a 400 stroker for my driver with 6 speed manual transmission, and will try to aim for some mileage as our gas is on the world's cost peak.....
Thanks,
Oyvind Mopar