I'm working with a 63 Dart here. As the car sits, it is a 170, 1bbl carter, 3 speed manual, 2.76 rear end, P215-60-15 rear tires. The only mods so far is the points distributor is curved for about 16 degrees of initial advance and about 16 degrees centrifugal advance thats all in by about 2000~2200 rpm, I was pinging with the vacuum hooked up so I disconnected that. As it is at 65 mph I turn 2200 rpm and pull 10~11" vacuum, and get 17.5~17.9 mpg (well slightly better as my speedo is about 7 mph slow since I added the rear tires and 2.73 gear).

Here are the other parts I have to work with:
a few 225's
an electronic distributor from a 77 Volare
a 3.23 ring and pinion
a 2bbl with carter carb
I also have a 833OD from an 83 pick up, I want to install once I can afford to have a driveshaft made.

My main goal here is to get better fuel economy.

I know I should upgrade to electronic ignition.
I know the 2bbl is supposed to give better mileage.

My main question is with the same setup of parts, will the 225 or the 170 get better mileage?
What would be the "best" gear, maybe lower then 3.23?
What would be the "best" gear with the 833OD?
Any other suggestions?

MY thoughts are if you have the 2.7 gears & those large rear tires youa re killing any off-line low rpm power of the 170-- defeating the hiway benefit.
I would 225 it--- as the mileage difference is minimal & the torque of the 225 really helps the low end-- I have done that swap in a 62 valiant/3.23/at car-- helps me get in /out of traffic---
read this forum --some guys give very detailed mileage ideas/real world testing----
Good Luck
Lawrence

My guess is that ultimate economy could be better with a 170, but given the range of buildups people put together, you can easily get better economy from a 225. There will not be a huge difference. What is your economy goal?

You NEED to run vac advance for good economy. The pinging could be that the vacuum can is not pulling the timing back at high enough vacuum (lighter loads). If not adjustable already, get one of the adj vacuum cans, which allows you to tune this vacuum pulloff point.

I suppose you know that my 64 Dart, 0.060"-over 225, makes about 250HP and gets 24 MPG hwy at 75 MPH? If 24 MPG is good enough, then a 225 will do just fine. Building an efficient motor is the trick (higher comp, optimized cam and ign timing and carburetion). Someday, I hope to build an economy-minded 170 or 170 with 198 crank and see how far we can go.

Lou

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Home of Slant6-powered fun machines since 1988

I agree with VDart; with those big tires and tall 2.76 final drive ratio, you're always going to have the carb's power valve wide open. (I also can't imagine this car being much fun or even particularly safe to drive around town...0 to 60 in what, 45 minutes? )

I would either build and carefully configure a 225, or keep the 170 but reconfigure the car. If you were to keep the 3-speed trans, then you'd want 3.23 rear gears at least. If you were to go to the 833OD with the 170, a 3.55 would be better and a 3.91 would probably be better still (easy "light-foot" acceleration in town, but a highway-flyer ~2.9 overall 4th gear ratio).

Carburetion with 170 or 225: either the 2bbl (yes, you can get better MPG with a 2bbl than with a 1bbl depending on configuration and tuning) or one of the high-economy 1bbl units (either a factory taxi carb or a Holley Economaster).

Ignition: You've got some recurving work to do. As has been said, vacuum advance is definitely necessary. You'll at least want to go to electronic ignition, and may want to do theHEI upgrade.

Exhaust: A low-restriction setup will gain you some MPGs. If you've got the cash, I'd point in the direction of Dutra Duals.

And as Lou says, there are lots of engine internal configuration and setup parameters (camshaft...!) that play a large role in operating economy.

Beyond that, you could get better MPGs by putting together and setting up a fuel injection system. It'd take a relatively large investment of cash and time, so do the math and figure out the payback period...

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

after reading this
http://www.slantsix.org/articles/Josh_Carb_Article.htm
i now want to find the 'Carter YF carburetor " since he states "It probably wouldn't make too much more power, but the throttle response and mileage should go up considerably."

i think the best thing to do first to help milage. is to find parts you can replace with lighter ones, aka weight reduction.

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1976 Plymouth Feather Duster
2002 Dodge Dakota 4.7l v8

That article needs to be revised again. The Carter YF is an ancient carb and the Cortez intake manifold is very hard to find. Your quote is misleading. The full quote is: "One side draft 1 bbl: If you have a Cortez motor home with the Slant 6 you already have this. The stock setup uses a Carter YF carburetor just like the ones on the old 6 cylinder Corvette. I'd like to try an SU or its Japanese-made Hitachi counterpart. It probably wouldn't make too much more power, but the throttle response and mileage should go up considerably."

The idea is one SU adapted to a Cortez intake manifold. Not a carter YF. If you really want to try this I would suggest getting an SU carburetor and modifying an aluminum 1bbl manifold to suit.

Joshua

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Joshua

how would you then go about modifing the alu intake for a SU carb?

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1976 Plymouth Feather Duster
2002 Dodge Dakota 4.7l v8

Cap the original carb mounting flange and add a new one to the side. To make it look nice you'd grind or mill off the 1 bbl flange and weld in a piece of aluminum. Fabricate a flange to match the new carb from a heavier piece of aluminum. Cut open the side of the manifold and weld on the new carb flange. You could do the same with iron, but welding cast iron isn't much fun. Since this is for economy the aluminum intake helps the overall goal too. The linkage is up to you. At least you've got a manual trans so no throttle pressure linkage worries!

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Joshua

Agreed.
Did they use the YF on the 235CID Corvette? Interesting. I knew they used them (in pairs) on the turbocharged Corvair. I'm not certain why throttle response and/or mileage would necessarily increase with the YF setup vs. a regular downdraft 1bbl. Remember, the Cortez 225 was rated at only 117hp or so at a time when the car/truck/van 225s were rated at 145. I have to think a fairly significant reason for the difference is the small-bore YF and the restrictive intake arrangement. This setup used a blockoff plate that bolted to the intake's normal downdraft carb mounting pad, but it wasn't just a plate. It provided for PCV inlet, and it also incorporated a chunky deflector "finger" that protrudes directly into the flow path right inside the (side) manifold inlet. The obvious purpose was to try and deflect the incoming mixture so the two central cylinders won't run rich while the outers run lean. It seems to me any such a sidedraft arrangement would need some similar provision, but I can't help thinking a less bulky, less restrictive design could probably be achieved.

I'm much of your opinion; an SU or Hitachi, properly built and configured, would likely be a much better carburetor for a single sidedraft setup on a slant-6. And now you've got me daydreaming about twin SUs...oh, wait a minute, there is an intake for that, and I think I might even still have one!

Yup. Look to Big Red (no relation) for info on how to do a good, clean manifold conversion like this.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

on another thought then what would you think of the Weber 32/36 DGAV using a 2 to 1bbl adapter? since they say this from that same link i posted.

"A Slant 6 Club of America member in Sweden used a Weber 32/36 DGAV carburetor on his Valiant wagon. He went from 19 highway/15 city to 22 highway and a little less than 15 city. This is in a wagon with 3.55 gears so you may do better. He reports "a definite improvement in torque" and "with a heavy foot the acceleration is much better than with the old carb". He blames this extra acceleration power for the slight loss of city mileage. He also used an adapter to bolt this carb to his 1 bbl manifold so power should be increased further if this carburetor was mounted on the 2 bbl Super Six manifold. You can read more about it in issue 54 of the Slant Six News."

this might be a better route then instead of a sidedraft 1bb?

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1976 Plymouth Feather Duster
2002 Dodge Dakota 4.7l v8

Dan,

I guess my writing wasn't clear. I don't believe the Carter YF wouldn't out perform a Holley 1920 or Carter BBS, but one of the larger SUs should. The 6 cylinder Corvettes used a pair of Carter YF carbs, the turbo Corvair just one. As for the horsepower ratings, well, the truck horsepower ratings appear to be more accurate. I think the same 2bbl 318 that was 230hp in a passenger car was only 177hp in a Dodge truck. Even so I agree the Carter YF equipped 225 would be rated lower than one with a Holley 1920, but the standard truck 225 isn't rated at 145hp.

I think the dual SU Lynx manifold would be superb once it was tuned correctly.

Evilsizer,

I feel for most folks with a stock or nearly stock engine that a progressive downdraft 2bbl like the Weber DGV on a Super Six 2-bbl intake makes the most sense. There is a DGV carburetor and adapter kit made for Jeep sixes to replace the Carter BBD. This would of course allow the substitution of the Weber for the Super Six BBD. Again, you're on your own for throttle linkage, but at least it bolts up to an existing manifold that's widely available.

http://www.piercemanifolds.com/
http://www.piercemanifolds.com/Catalogpages/jeep.htm
http://www.piercemanifolds.com/Images/Catalog/K551.htm

Joshua

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Joshua

Harley used (they've gone to EFI like everyone else) a 40mm CV carb for years on their bikes.

Same basic principal as an SU, but probably much easier to find (and cheaper) than a SU carb as owners replaced them for other carbs for supposedly more performance. There's alse a 44mm version of the CV (but that'll be expensive since it's one of the performance upgrades).

The 40mm CV's show up on ebay all the time.


Plus CV's are easy to tune.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I ain't not gonna undisbelieve it
Agreed. I'd probably pick a 1¾" SU (HS6 or HIF6), or its equivalent from Hitachi.
230 vs. 210 in the car vs. truck 318. I agree the truck ratings were probably closer to being accurate for the car engines, but given how fanciful the BHP ratings were on pretty much all engines back then, I'm inclined to think that the car and truck numbers were equally optimistic/overstated. At this late date, who knows? :shrug:
I go back and forth on that. Some days I agree, other days I think there might be mixture distribution issues...guess I will have to try it and see!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It is not really that bad, once I get it moving, but yes my foot is on the floor more then it should be. It is the first 40 to 60 feet that the clutch suffers the most. I'm really thinking the 3.23 has to go back in.
I searched here and most recurve threads seem to be preformance oriented rather then economy, could you (or someone) suggest some starting specs or point me to a good thread?
Would love to have Dutra Duals, but thats way out of the nonexistent budget at this time, maybe one day. I am going to try to cobble up a bigger headpipe out of what I have laying around.
If I could get to the mid 20's I would be really happy, if I can get in to the low 20's that would be ok untill I could scrape the money up to build an engine.
I will have to hook it back up and tune it some more. I do understand that it is supposed to help mileage, however when I disconnected it I picked up 0.75~1.0 mpg, this was on the same drive on subsequent days. Could this mean am running to much timing? Or that I just had the advance pod way out of adjustment?
No I did not know that. It gives me hope though. I don't have the money to open up the engine right now, so I am limited to using pretty much what I have on hand.


It seems the general consensus here is I need to put a 225 in with a 2bbl on it, put the 3.23 back in, put the electronic distributor in with the vacuum advance hooked up, try to make a bigger headpipe, and tune from there.

Hard to say. My previous car ['63 Valiant, automatic, Holley 1920, Pertronix with 3.23 rear end and 170 motor] delivered 25+ MPG on the highway. Sometimes hit 26, best of 28. I drove it 110,000 miles and averaged 20.8 MPG.

My current ride ['64 Valiant, 3-speed, Carter BBS, Pertronix with 3.55 rear end and 225 motor] is more consistent. I've averaged 24.0 MPG over the past 10 months. I've driven it 42,000 miles and averaged 22.0 MPG.

Careful driving habits cannot be ignored when pursuing maximum MPG. I never exceed 55 MPH on the freeway. I look ahead at traffic lights and coast in neutral when I foresee having to wait for a signal.

These cars can deliver far better fuel economy than one thinks.

Let the record show that it still has the OEM 44 year-old clutch, too.