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Discussion Starter · #1 ·
Anybody doing it? I've set it as my goal, without spending stupid amounts of money on either fuel injection or an overdrive trans.

Vehicle: 64 Camino, 3300lbs with me in it
engine: 454, 9.5:1 compression, rect port 990 heads, solid roller cam
trans: Muncie M-21
Rear: 1967 12 bolt posi, 4.56 gears (will change)

Best E.T. to date: 12.17, backed out of it at 3/4 track
launching at 4000 and not spinning the tires

Devin
 

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There is no way you'll ever get a rectangle port 454 with a solid cam, M21, with the amount of gear needed with a M21, to get anywhere near 20 MPG. That engine just will not have the low speed efficenicy needed to get that kind of mileage without FI and overdrive trans. To run 12's and get 20 MPH I with a BB, I would lose the rectangle ports, the solid cam, and the M21. I would replace the heads with ovals, a good hyd roller, and an Overdrive (TKO600), then change the rear gears to 3.31's......add nitrous and stir vigouriously. It would run low 12's (maybe high 11's on a good day) and pull down in the low 20's MPG.
 

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well i toyed with the idea of good gas mileage without overdrive and run as fast as i could in the process with a bbc.

so i built one. i came up with 17-18 mpg on the highway and was running 13.50 @ 107.19 mph with a 2.73 posi track.

the car could have gone quicker for sure but i put a 12" stall in it to allow no tire spinning during launch. plus this made it really consistant for racing.

i could stage at 1400 rpms and mash the gas peddle and would not spin out of the hole even on 245/60-15 uniroyal tires. my 60 ft times was 2.10 this was a 4000 lbs plus car by the way.

the engine was a 396 10.5 to 1 motor on 87 octane fuel with delta grind cam 233/239 @ .050", rpm intake, 3310-2 carb with 72/80 jets summit headers 2 1/2" pipes to the full boar mufflers and 2 1/4" tail pipes.

engine ran really strong from 3200 or so rpms to 6500.

i started off with 2.41 gears but that put my rpms way to low in the 1/4 mile at the finish line.

the 2.73 gears gave me about a 6300 rpm finish line rpm

i knew if i would have ran a 10" convertor with this combo with a stall closer to about 3500 rpms i would have hit 12's but i really cant say how much my gas mileage would have taken a hit.

there was more tuning to be done it took about 50 1/4 mile passes to get the combo sorted out from low 14's @ 102 mph to 13.50 flat at 107 .19 mph

this took 3 trips to the track to make my gains. and on my last outing my car ran 13.50 flat 4 or 5 passes in a row with no cool down, i was hot lapping it for the fun off it since i was happy with my results for the day.

so i think it could be done with a 454, maybe some peanut heads? just a thought. or at least the oval port heads and some 2.73 gears. thru some trial and error im sure it could be done with a carb that is on the edge of lean but have enough fuel in the secondarys to make the power as needed.

i think if i would have spent more time with jetting and timing curve on mine i could have increase both performance and mileage.

shoot if you just went on cubic inches alone over my 396 to a 454 and you should have enough power to pull it off (run 12's) not sure where your gas mileage would be at.

heck my combo in a car that weights 3000 lbs would hit your goals i would think.

i think its possible. not sure with rectangle ports.
 

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Discussion Starter · #6 ·
I would love a tko600, but it's just not in the budget at the moment. I will be swapping out the 4.56s for either 3.73s or 3.55s in the not too distant future. I need to get the carb dialed in, as it runs way rich at the moment. I also need to add a vacuum advance to my dist. I want to have about 50 degrees of total timing at cruise, backed down to the current 36 at WOT. The cam may get swapped out for something with shorter duration, but lifts on solid rollers all seem pretty close.

Devin
 

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Buy the Audi R8 12 cyl turbo diesel. 500 hp, 740 ftlbs 23 mpg...

Just kidding. I dont think it is even available yet and when it is, it most likely will not be availlable in the US. These darn turbo diesels just keep impressing me.

http://www.autoblog.com/2008/01/13/detroit-2008-audi-unleashes-its-diesel-monster-the-r8-v12-tdi/

In reality, I think it will be a little difficult to reach your goal. These big blocks really like to eat gas. For what it would cost to actually reach your goal with the big block, I think you could build a completely different motor. (lsx or something) What I mean is a really small cam, heads, carb... along with a turbo and an overdrive tranny for the big block to get the mileage and times you are after. As has been stated, nitrous is also a possibility, but I still think you would need overdrive in order to get any performance out of it.

If you buy a different set of gears, just know that 3.55's will put you right around 70 mph at 3000 RPM with a 28" tire. That is what I have. 3000 RPM is still not a great cruising RPM for gas mileage. (I only get 5-7 mpg) If you were really trying to get better gas mileage, I would shoot for ~2300-2500 at highway speed. As an example of what this would take without an overdrive tranny, you would need a 2.73-3.08 gear with a 28" tire at 70 mph.
 

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Discussion Starter · #9 ·
Worked on it some today....got to drive it for the first time in over a year. Man did that feel good. Started on getting the carb dialed in. Had done some reading previously on tweaking Demon carbs, and took it too far. I had the IFRs leaned out so far the best I could get at idle was 30:1 air/fuel ratio. Never woulda figured it could even run there. Made some progress, got it down to the low 20's range, but ran out of time. Hope to do some more tomorrow.

Devin
 
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