Streetable 12 second 20+ mpg slant six?

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1970boy

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Hey FABO ive got a 70 dart swinger with the /6 and and want to be able to do mid 12's or better in the quarter and get 20+ mpg without nos. Is this achievable or am I in dreamland?
 
Not without turbo or some kind of power adder.

Slant 6 head is the weakest part, untouched your lucky to make anyway near 200 hp ported could make up to 300 hp but to get mileage you want to be in the 0.8:1-1:1 hp:cid which is 200-225 hp over 250 hp you'd start to have more of a street strip engine.
 
I just gotta ask...... Do you really want to beat your head against the wall with your proposed agenda?

JW
 
Weight.. Its all about weight. If you can get the car down to the 2500 pound range, along with some serious porting, intake and exhaust systems, converter and gears, you can come close.
It won't be easy!
 
more or less dreamland I had a 12 sec leaning tower of power in early 90's I was running 12.teens @ 106ish mph. my personal best was 11.98! Fast for 1993! I took a LOT of money and hurt a lot of feelings with it, but was not really a driver. I stripped everything i mean everything! fiberglass fenders, bumpers, hood, no hinges lexan side windows 2 plastic racing seats & no dash I stripped everything. I got it down to 2272 with me in it i ran 9" drums manual steering manual brakes 3.91 gears 8.5 in slicks tf 904 something crazy like 4k stall trans brake all that with 225 slant although I was cheating with early aluminum block again save weight. try y headers duals 4bbl running" race fuel" Credit due to my shop teacher who helped me build motor in school. all that for 12's it can be done practical, probably not
 
Seeing as you posted in the forced induction forum I am going to assume that you mean with a turbo or a supercharger. In a word yes it can be done. Best bet is probably a turbo but it won't be cheap unless you are real creative. 12's with a turbo won't be to hard, just pricey. Talk to Prine, he will help a lot with a turbo setup.

Jack
 
Coyote Jack said:
Seeing as you posted in the forced induction forum I am going to assume that you mean with a turbo or a supercharger. In a word yes it can be done. Best bet is probably a turbo but it won't be cheap unless you are real creative. 12's with a turbo won't be to hard, just pricey. Talk to Prine, he will help a lot with a turbo setup.

Jack
Click to expand...
Talk to who???
 
There are a lot of set up here for /6 turbo set ups, just browse through them and if you can get all the pieces which most kits can be found, universal ones that is and cut to fit. Some members have come up with great ideas to use the stock exhaust manifold to custom ones. Turbo is your best option, and easy on internals.
 
Lots of /6 turbo info out there, you can meet your goals easily. Basically what you're gonna need is:

Rebuilt short block
Valve job and scrub the ports out of slag
Possibly bigger valves
RV cam
A heavy wall log manifold would be best
Match a turbo to your cid and rpm
Carb works well or you can go FI for more reliable power
Gearing in the 3:23 range
 
I think it can be done. Turbo + head porting + 4 barrel intake + blow through carb. Turbo allows you to make power for the 12's and easy throttle will keep the MPG up, provided it is geared properly.
 
Yes its do able with a turbo, but id go turbo 360. Cause the 90% of time you'll be just driving off the engines own power.
 
273 said:
Yes its do able with a turbo, but id go turbo 360. Cause the 90% of time you'll be just driving off the engines own power.
Click to expand...

Then he wouldn't get 20+ mpg

If he has a /6 when he's driving NA, which is 90% of the time, and has a 12 second car when he spools it up, that would be sweet.
 
20 mpg in town or the highway ??
I've had dozen of /6 cars I wouldn't brag about any of there mileage my 318 5 Ave gets about the same. If you don't think you could get 20 with a mild 360 then start with a 273 still miles ahead with power potential over a /6. 273 is only 50 cid bigger but it has 8 intake ports vs 6 and the 273 flow stock what a fully ported 6 would plus you can add a overdrive easy.

The problem I see with a turbo six is 90% of the time your driving a stock powered slant six around.
I'd rather have a car that got slightly less mileage and was a blast to drive 100% of the time.

My 5.9 jeep gets 13 mpg in town and about 20 on the highway. If you installed that in my cuda both of those numbers would go up.
 
I don't see much work involved to get a V8 20+ on highway, its 20mpg in the city that's the issue. Your jeep is also fuel injected and overdriven, unless it's a much older jeep. Not trying to fight ya, just saying the OP said he wanted a /6 for fuel mileage and the torque of a V8, while being streetable. Which is really the beauty of a turbo; you can have a smaller stock engine for light work and double the power when you need it.

To make a 12 second NA V8 car, you're going to need heads, compression, more CID, cam, exhaust, and the worst thing for the highway - low gears. For a turbo car it's basically a stock rotating assembly, small cam, lots of fuel available, exhaust and turbo plumbing, low compression, and high gearing.

Lots of V8 guys ask what LA head is better than the other to pick up a little port flow. Turbo does it all for you when you put a 16psi head on top of that valve, it doesn't really care that much. Not saying big ports, cam, and valves are a bad thing, but you're still waiting for the atmosphere to cram in the mixture.

In my opinion, the only time you're driving a turbo 6 at a stock NA power level is when you're sitting at a stoplight or maintaining speed, which is exactly what you want for mpg. You'll never really feel the stock power of a turbo 6 because as soon as you need more power from the engine, the turbo spools up and off you go.
 
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I'm not trying to argue either. But Everyone seems to think small engines is the only way to get mileage but it take a certain amount of fuel to get your car moving (weight) no matter the engine size. 20 mpg in town is a hard number to get even a lot of modern cars (similar weight) with all the tricks. I hated the lack of power my /6 had off the lights in town. If the OP wants to go the/6 route it's up to him just trying to say in the end he may only gain a couple mpg over a 360 but at a huge lost of performance and 273 would probably be the same mpg but have a decent bump in power.
 
Yeah it's all based on what the OPs final goals are. The one thing that makes up for the /6 power vs the V8 is the equalizer of the turbo. I be willing to say that a stock 6 could make similar hp before 3000 rpm compared to a big cammed 318. After that, it's on boost. Plus the 6 is built stronger than a 318 so it's turbo-ready, and equipped with super low compression pistons. V8s make power no matter what with a lot of cheap, proven combos from mild to extreme. It's all about what ya want.
 
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