Daughter needs Gas mileage from 273 commando

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67Dart273 said:
He mentioned D4B which is the early 273 dual plane, I guess the forerunner (no pun) of the Performer
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Ahhh, yea, I know, someone mentioned single plane intake. I mentioned Performer but......
Thanks Toolman Mike. I missed/by-passed that in my head. Swapping heads is not cost effective at this point.

Love the meter!

There was a thread on a guy that did a mileage experiment. His A-833 O.D. was helping in a 30+ mpg ride with a 318. Rear ratio I forget.
 
rumblefish360 said:
I would so NOT use a sine plane intake. Stick with the dual plane. Trade for a Edel. Performer if anything.

Open air element cleaner
2-1/4 exhaust pipe with an H pipe

You should so well on the Hwy.
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Not understanding; not a challenge to your experience but trying to understand why. Dual planes have more twists and thus suffer for breathing efficiency. Single planes can have more issue with equal mixture distribution at lower RPM's but use a moderate rise manifold, a torque cam, and not the largest runner sizes and that will tend to even out. And a torque cam will not cause the reversions that are common in wild cams that send a lot of flow distrubing pulses back into the intake. So, IMO, there is an association of single planes with high RPM, wild cam apps that holds true only in certain conditions. So just curious.....
 
Dual planes have more twists and thus suffer for breathing efficiency.
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While there is merit in this thinking, the single plane did not hold up in practice. I tried. There could be something to it. I could not find it. What I have found is a poorer fuel distribution and low RPM speed torque suffered. A slight driveabilty down turn in the single plane use.

The dual planes added torque is a big plus. The engine was just simply more efficient in low speed torque production. The car made better use of the added torque. Around town driving was better. Considering the engine being discussed is going to have a combination of driving conditions, the dual plane will do the trick.

My question to you is, what single plane intake would you suggest? I'm not in a position to try it out yet and it may be a good while before I can. Though when the time comes, I'll try it. It's a MPG experiment I want to fuss with. Currently, I'm seeking a 318 to rebuild and a member here in North Jersey (BVoelzke) has one I'm willing to pick up.
(He is relatively close to me.)
I'm also going to be seeking soon a A-833 O.D. bellhousing.
 
Yeah, I know; the dual plane with the longer runner length and the smaller runners should be better; all the lilterature for the single plane even in the day (mid 70's) said it was not as good for low RPM and drivability. But I hit the right combo with that and the smaller carb and torque cam. I was worried that I had blown my $$ on the single plane as a lowly Navy E4 but was really happy with the end result. When I can dig the 351C engine out from under the huge pile of used rally tires, I'll let you know; wish I could remember the model off the top of my head. I suspect the small primary barrels of the carb (Holley 6619 if I recall right) and the torque cam had a lot to do with it; that would keep the flow velocities up, even with the vary large intake stock flows of the early 70's 351C heads and the single plane. So the single plane was not a liability and I figure helped the top end flow to help make the RPM range so wide. Drivabilility for the combo was like a stock engine, never bogged or rough idled for a second; again, no foolin'.

Later when the headers rusted out, I was short of $$ and put the stock exhaust manifolds back on; sure stifled the power, and hurt the mileage.
 
Can you remember the intake used?
Any recommendations on why to try on my 318?
 
My goals for my 65 Dart 273 are about the same - efficiency and smooth running are first priority. I installed a hydraulic cam, the common RV/Torque one, with Rhoads leak-down lifters. "340 TA" ball & cup push-rods (Summit) fit fine. The adjustable rockers make it easy to setup the Rhoads lifters optimally. My eventual plan is to install a Holley Commander 950 for fuel and also control spark timing (via a GM 8-pin HEI) and knock sensor.
 
I am like a Sponge ,trying to absorb all of this great info ! We Thank You ! Tim (Dad)
:thumleft:
 
BillGrissom said:
My goals for my 65 Dart 273 are about the same - efficiency and smooth running are first priority. I installed a hydraulic cam, the common RV/Torque one, with Rhoads leak-down lifters. "340 TA" ball & cup push-rods (Summit) fit fine. The adjustable rockers make it easy to setup the Rhoads lifters optimally. My eventual plan is to install a Holley Commander 950 for fuel and also control spark timing (via a GM 8-pin HEI) and knock sensor.
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I wouldn't recommend the large 4 barrell injection on a small engine. I had a 950 on a 454 Chevy in my old tool truck and the drivability was good but didn't get any better mileage than the ol' Quadrajet.
 
I ran a 318 with a stock 340 cam with rhoades lifters with a stock 340 dual plane, Holley 600 vac sec, stock exhaust manifolds, and dual exhaust.

With 2 bbl heads and intake (10.5 pistons) it idled at 24" mercury, but would detonate.

I replaced the heads with 77 360 heads that I got cheap and put a stock 340 square bore intake on it. (to bring the compression down to 9.2 for pump gas). The manifold vacuum was then 22.5" mercury. It could get 17.75 mpg on the highway with a 2.76 gear 7 1/4 axle, however I ended up breaking 3 x 7 1/4 axles in 4 years and then went 8 3/4. It could go when you needed it to, but economy if you drove it right.

Also, put a vacuum gauge in the car and show her how to use the gauge to get better gas mileage.

I would definately keep the D4B intake, and run an electric choke on the carb.
 
krazykuda said:
.... put a vacuum gauge in the car and show her how to use the gauge to get better gas mileage.
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GREAT IDEA!

Recommend a 650 cfm or less carb with air valve secondaries. Because of the primary/secondary disparity, the Thermoquad and Quadrajet make the cut, too. This recommendation, IMHO, will preserve throttle response while allowing a bit performance to shine through. The benefit of the air valve recommendation is that the secondary does not open until the engine actually demands the extra fuel. While I can't complain about the DB4, the Performer can handle either a squarebore or spreadbore carb.

FWIW, I have a 625 cfm AFB, Performer, 302 heads, and a Summit (Crane Fireball) 6901 cam on a 318 in my Demon. Even with the 2.76:1 gear in it now, it's fairly peppy. Couldn't tell you about fuel mileage as it isn't a DD and when I do drive, it's not the right sort of situation to use for a good opinion.
 
2 Darts said:
GREAT IDEA!
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Yes, that's how I learned to drive "economically". I had a few 67/68 Barracudas in my day. I installed a vacuum gauge in the dash and used that to drive with maximum vacuum to get better economy.

I also had an '85 Laser XT brand new with the navigational computer that had a button to monitor current fuel economy. That also helped me learn to drive economically. I liked to get it up to 70 or more on the highway and put the clutch in and coast, then watch the economy meter max out at 99 MPG! It was a fun game.... I used to be able to get 32-34 MPG on the highway with it, and about 26 MPG city.

But it's easy to put in a vacuum gauge and tell her to try to drive with as much vacuum as possible.
 
I totally agree with the vacuum gauge, driving style is the largest factor when it comes to MPG's My son can take my PT cruiser from 28 mpg down to 16 mpg just by getting behind the wheel. Now for a little old school technology, find an Offenhauser dual port intake manifold for the 273, they are usually pretty cheap(not more than $75) and use a small 5oo cfm carb between that ,the electronic ignition, a 2.94 gear and some lessons with a vacuum gauge that should put you firmly in the 20's
I bought a Shelby Charger new in 1983 with the carbuerated 2.2, at 105 mph steady cruise it would get 42 mpg. At 55 mph it would get 28 mpg. You have to find the sweet spot on the tach and tune the whole car to run at that RPM
 
hemichuck said:
My son can take my PT cruiser from 28 mpg down to 16 mpg just by getting behind the wheel.
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My oldest son also has that "skill".... :banghead:


I am going to use the vacuum gauge method on him when we get his mopar running. :goodman:
 
O.K. here is what 273 Motor I have GOT NOW top to bottom:
1 - I'm running a elect. choke, 600 Holley with Vac. 2nds, 65 jets, dual line float bowl conversion kit ,center hung floats.
2 - D4B Ebelbrock intake
3 - Factory heads, stock valve job,hardened exhaust seats and new exhaust valves, spec. springs to match cam.
4 - Bored .030 Badger #P275 pistons (don,t know/can't figure comp.ratio)
5 - Wolverine # WG5036 cam, solid, 278 dur,.479 lift intake & exhaust with 110 center line.
6 - 2:96 gear with 26" tall tire.
The long block was together when I bought this "Basket Case". I got the Carb. Ignition and Intake afterwards.
Stock rebuilt 904, stock converter, all new ,that is all I know about trans., not installed yet.
Educated Ballpark guess/projection of what to expect with the combo I have to work with now. Overbudget now (always the way it goes) only SMALL changes can be done now. No Head swap/changes can be made at this point.

A Bodies/Mopars are totally out of my scope of knowledge and I know some of you can help me with a "Seat of the Pants" point of view.
Thanks, Tim (Dad):happy1:
 
Badger p275 is a 2 barrel piston. Advertised 8.8 to 1. The specs are on the NHRA site under 273. You have small chambers with the 64-65 heads. Sounds like a great build. The only thing I'd change is the cam, for your intended use. Not exactly a mileage build. I say it'll pull past 6K and get there quick. You better change that tranny fluid and filter. Best adjust the bands and pump up the pressure also. Best mileage will be at higher speed than 55, like Hemichuck says above. You will just need to find where that is. Pretty wicked car for a youngster. You will love it, and at the same time you may be afraid to turn it over to your daughter.
 
Well ,I will drive it from time to time ( he he ) but I do plan on fixing it to where the 4 bbl. won't kick in. maybe a "Hidden" lawn mower style cable leading from the passenger comp. to Carb. secondaries locking them. Just a thought......:D
When do you plan on moving to S.C. ? Do you think the car will be too fast ?
 
Is the Cam that ratical ? I mean ,on a street car / Driver? If you all think the Cam is too big ,I am willing to hit the wife up for the x-tra $ but budget is all but gone. Have to be SURE before spending more money and you all know what I am saying.....
 
one mile said:
Is the Cam that ratical ? I mean ,on a street car / Driver? If you all think the Cam is too big ,I am willing to hit the wife up for the x-tra $ but budget is all but gone. Have to be SURE before spending more money and you all know what I am saying.....
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I don't think that the cam is that bad.


The stock 340 auto cam is 268/276 duration.

This one is just 2 more degrees duration than the exhaust on a stock 340. This will idle a little bit rougher than a stock 340 and perform well also. Crane does not even list a solid cam with this "small" of a duration. Unless he wants to switch to hydraulic and then maybe a milder cam would make more economy.

As far as economy, in one of Larry Shephard's old books, he recommended the stock 360 2 bbl cam as the best cam for fuel economy. It was 252° duration and like .425" lift. My father had a '76 Charger with a stock 360 2 bbl that would get 20 MPG on the highway (and had a 25 gallon take = 500 miles between fill-ups). We would have to take a pit stop to pee before we had to stop for gas on long trips.
 
You want better gas mileage, try getting a speedo gear that has a few less teeth in it :)

Ok that wont really help, but maybe she will drive slower and it will look like she is getting better gas mileage. :)
 
toolmanmike said:
I wouldn't recommend the large 4 barrell injection on a small engine...
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You can install various injectors. They are standard Delphi TBI injectors. I have one Commander 950 with their smallest TBI (600 cfm, I recall), which might be good for my 273. But, I was planning to use that on my 383. For the 273, I have a Magnum manifold (MPFI) that I hope to use (yes, I know the bolt angle issue).

The 4 injector TBI's could be more efficient than say a Holley Pro-jection 2D TBI since you normally run on just 2 injectors until the secondary throttle plates open. Problem is most people install the biggest injectors they can find, then complain. Same deal with carburetors. Don't over-carb. It doesn't give more power. Match the carb to your max airflow and be honest about that. For a 273, a 370 or 450 cfm carb is a good fit, but they are hard to find. The Holley Economaster is one.

The best way to get good mileage on the highway is to follow a semi. I did see the MythBuster's episode where they supposedly discounted that, but my 2002 T&C 3.8L has an instantaneous mpg indicator and I get 33 mpg at 65 mph behind a big rig vs 24 mpg normally. I don't follow too close. Indeed, other cars sometimes pull between me and the truck. I usually only do that on a long drive to LA, when I find a truck or motorhome that doesn't have the 55 mph governor common here.
 
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