Gas price going up // Rethinking the new project car

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^^^I think AJ meant to say "overdrive?"!
Heck, my '95 Cummins Ram that weights what ? 6500 lbs. with 4:10 gears, gets 18 empty, doing 75 in OD!! Heck yea!!
 
AJ/FormS said:
I bumbled thru the first page of responses, but not really wanting to sift thru all the off-the-wall stuff, to see if anybody got to the meat and potatoes........ so:
There is a simple solution to your dilemma, namely; overdrive.
I like what @66fs said , and anyone else that is on track with him.
Every time I offer opinion, people jump on me, so I'm not gonna do that this time. Instead I'll tell you what I actually already did.
Like my Avatar shows; final iteration is 367/A833/3.55s
I chose each of these components with fuel efficiency as the primary consideration, and modest power as a secondary.
I had at least One example of every LA SBM, in my shed.
I had at least One example of every transmission that would bolt up to any LA, both automatic and manuals.
I had at least One example of every A-body rear-end, except a Dana, and
I had at least One example of nearly every rear gear from 2.45 to 5.13 skipping; 3.73s and 4.56s
These were my options.
I chose the manual trans for efficient power transfer, to gain mpgs, so I could run a bit more cam.
I choose the 8.75 for it's easy-swap pumpkin.
I chose 3.55s for their dual-purpose versatility
Knowing this would be a modest performance combo, and
knowing that the 367 could fall together cheap at near-zero deck, and
being desirous of the 1.7 r/s ratio for piston dwell time at TDC, and
knowing that a longer stroke would allow a lil more cam before loosing cylinder pressure,
I choose a 360..
To run a smaller cam, I reasoned that this engine would need some extra cylinder pressure. To get some Power back, due to the loss of valve duration, I choose a better-flowing head. To take advantage of the piston dwell, I reduced the cruise rpm drastically with overdrive. To get out of the rut of a crappy starter gear, I choose a trans with a 3.09 low in it. To get low-ET back, I installed a Gear-Splitter.
Did it work?
Hell yes!
on a certain Daytrip-test, she pulled down 32mpg USg
At the track, she went 106@12.9 on 245 street tires@3650 pounds/me in it.
This is what I have already done.
this is not imagination,
not puffed up keyboard tickling;
this combo sits in my carport as we speak.
And you can come to my house with a trailer and a bag of cash and take her home. Or if you wait a few weeks, I'll change the gas and oil, and then you can fly over and drive it home.
If you want details;
some most excellent fellow FABO member bought me a Gold membership (thank you whoever you are), so I now have lots of room for Conversations. I am semi-retired so I got lots of time to talk....
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Well you are getting closer. You also need to consider the OP's goal and what he has on hand. Frankly, I would not consider a GV O/D, I just don't want that much change. I've run the Mopar O/D manual box for years and it is a simple bolt in, other than switching the main case (if you don't have a O/D bellhousing), flipping the 3-4 arm down and getting the 3-4 rod to mate to it. A 273 or 318 can easily make enough power to cruise at 70-80 mph with a few simple mods at O/D rpm in a 69 Valiant. So what is the torque multiplication of 3.91 gears and a 3.09 1st gear? 12.08? That will get you started quick, even with a warm 170. Been there and done it.
 
I wouldnt mix the 3.91s with the 3.09 1st unless I had pretty tall tires . You are getting close to grany gear ratios with 14" tires. That would get old quick ! 3.55s would be the sweet spot .
Actullay I had an 82 D150 with a 318 and 833 OD combo that I installed an 8 3/4 in from a friends old 73 B100 van.
Turned out it had 3.91s in the back ...lol Worked great but the truck had 30" tall tires.
 
If just reaching 20 mpg hwy is your goal, a 318 with OD can probably do it. Probably have to be good at tuning the carb and ignition for that but that's me.

Had a 360 Magnum, standard A-833, 3.23 ring and 225-60-15 tires (25.6 OD) -> drove it to work for a week before I moved, some of it was 50-55mph and the rest was 70. Got 17 mpg with a 600 holley. That combo turned 3000 @ 70.

Currently I have a 340 with the T56 magnum with the 2.97 1st and the .63 OD which turns about 1900 rpm at 70. Also have EFI so its much happier at low RPMs and I have overrun fuel cut but even moderately "in town" stuff when you are nice to it is over 15. The pandemic put a damper on some of my plans for going on a trip with it but I would never expect it to get more than 25 mpg no matter what, 21-22 would be quite good actually.

I will say that it has no problem pulling any hill at above 1400 rpm so 50+ it can be in 6th. I use the .8 OD gear down to 40 mph quite often. So an A-833 OD is about 1/2 way in between. You'd pull about 2200 at 70 with the A-833 OD if you had the same gear and tires as me. I think much above that your fuel economy will really drop off fast.

I have to also say what was achievable from a fuel economy standpoint with non-ethanol gas isn't achievable anymore. Its at least a 3-4% fuel economy loss due to the energy.

If you have dreams of getting 30+ MPG with a V8, I just don't see that as realistic with one of these bricks unless you only drive like 50 mph everywhere.

I had a 1994 Oldsmobile Cutlass Supreme Coupe with a 3.1 V6 160hp version, Sequential EFI, EGR, ran 17:1 AFR at cruise, 0.29 Cd so very slippery, similar weight to at least the fatter end of the A-bodies, 4-speed auto, with 0.705 OD gear, and a 3.33:1 final drive with basically the same size tires as my Duster. I think the drag coefficient helps that car a lot, but if you went 65 on an entire tank of gas and were nice to it on the not especially hilly terrain here in the great lakes region, it could get 32-34 mpg fairly easily on a full highway trip. Freeway commuting to work it would get like 23 when you're going 75 and a trip going 75 was like 29 or 30.

My Dad had a 1990 of the same chassis car, but with the 2.3 Quad 4 HO 180hp, Getrag 282, 3.61 final drive and a 0.72:1 OD. 65 mph it would get 38-40 mpg and if you went on a trip at 75 it would get 34-35, commuting it got 29. Mind you, other than the powertrain and the front bumper, it's the same car body.

I currently own a 2012 Chevy Cruze 1.4 Turbo (so this is an 83ci engine), M32 6-speed manual (this is not an ECO with the super tall gears), 3.83:1 final drive and a 0.74:1 6th. That will get 36-38 on pretty much any highway trip and if you went 65 it would get 41-43. Now at the same time this has enough power to maintain speed in 6th at 45mph. Also roughly the same size tires as my Duster. 30 mpg city. These cars have to run richer due to emissions because lean= NOx

In summary, a smaller engine that can do the work and keep the RPMs down at the same time will get better MPG. Also our A-bodies are not aerodynamic. You stay with a 318 or 273, I can see maybe low 20s. I don't see much of an improvement with a slant six if you want to go 70-75 with traffic because its not a very powerful engine, especially for its displacement. There's a balance there. This is why anyone would consider the pentastar. You feed the same displacement and it makes double the power, it would follow its more thermally efficient.
 
mbaird said:
I wouldnt mix the 3.91s with the 3.09 1st unless I had pretty tall tires . You are getting close to grany gear ratios with 14" tires. That would get old quick ! 3.55s would be the sweet spot .
Actullay I had an 82 D150 with a 318 and 833 OD combo that I installed an 8 3/4 in from a friends old 73 B100 van.
Turned out it had 3.91s in the back ...lol Worked great but the truck had 30" tall tires.
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What would you do with a 3.09 and 4.56’s or 4.88’s?
 
Running 4.88 gears would give you a 1st gear speed of 9.5 mph @ 2000 rpm
And a top speed of 22.42 mph @ 4800 rpm.
Remember we built the engine for efficiency so it not going to rev out very far ...
 
When was the latest the OP responded? Are we just wasting our time now?
 
mbaird said:
No .. we are having mpg fantasies... lol
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I guess. It just bothers me how sometimes we spew out good, pertinent information only to have the OP go MIA. I mean, nobody gets paid around here. Nobody hardly ever bothers to say thanks either.
 
RustyRatRod said:
I've always just built cars like I think about or plan and let mileage fall where it may. I never have let mileage dictate how I build anything.
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Its just another way to have fun with Mopars. I drive my cars a lot and would like to have one that doesnt consume a weeks pay every month .
I dont require 400+ HP to enjoy driving them . I have cars to satiate that need when it arises .
 
'68cuda416 said:
You guys are comical and that also translates over into into a lot of your builds if i'm being honest
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I am tired of hearing you gripe and ***** about other people's cars. Let us build our cars the way we want and butt out I am blocking you. I do not want to hear any more of your negativity.
 
RustyRatRod said:
I've always just built cars like I think about or plan and let mileage fall where it may. I never have let mileage dictate how I build anything.
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Me too, It is funny how power/efficiency works to up your mpg at the same time. The 273 and the mpg was a complete surprise. But that was in the 80's in South Dakota where you could cruise in highway mode for hours. The 170 was a lark. I had read about the Baby NASCAR 170's and felt I had to pull 273 because of compression issues. Not as hot as yours, but no one would believe it was a 170. That darned thing would also top 30 mpg in the same car and same set up. I do believe aerodynamics played a roll also, since they were in a 64 Barracuda.
 
mbaird said:
I wouldnt mix the 3.91s with the 3.09 1st unless I had pretty tall tires . You are getting close to grany gear ratios with 14" tires. That would get old quick ! 3.55s would be the sweet spot .
Actullay I had an 82 D150 with a 318 and 833 OD combo that I installed an 8 3/4 in from a friends old 73 B100 van.
Turned out it had 3.91s in the back ...lol Worked great but the truck had 30" tall tires.
Click to expand...

3.91 x .73 is the equivalent to 2.85 gears.
3.55 x .73 is the equivalent to 2.59 gears.

That is how I pick them. 1st gear falls where it will.
 
If anyone should use the Mopar A833 overdrive box; just remember, that the m/s gear only has 20 teeth on it, and no more than 2 or 3 of them are transmitting power to the cluster. In my experience, they will not take ANY abuse, and then, Zing! / you are walking. And one out of three times the broken teeth take out at least one other gear; in my case the input gear, and that cost me a tow-job, in addition to another gearset.
I urge you NOT to run a CF-II disc, cuz it shows no mercy.
After 4 years and three broken boxes, I gave it up.
 
I think ill sincerely will go with a carbed/cammed 5.9 magnum and 46re overdrive / manual reverse valve body....and gears , in a 2 500 pounds valiant i think it will kick *** and be cheap.
 
AJ/FormS said:
If anyone should use the Mopar A833 overdrive box; just remember, that the m/s gear only has 20 teeth on it, and no more than 2 or 3 of them are transmitting power to the cluster. In my experience, they will not take ANY abuse, and then, Zing! / you are walking. And one out of three times the broken teeth take out at least one other gear; in my case the input gear, and that cost me a tow-job, in addition to another gearset.
I urge you NOT to run a CF-II disc, cuz it shows no mercy.
After 4 years and three broken boxes, I gave it up.
Click to expand...

Been running one for years and no problems so far beyond wearing out the 2nd gear synco due to the huge RPM drop. With a Dual Friction clutch, too.

Now, my 360 isn't any kind of a powerhouse either. So maybe that is the difference.
 
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