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Improve Fuel Economy on 360

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Forum Name: AMC V8 Engine Repair and Modifications
Forum Description: AMC-made V8 engine mechanical, ignition and fuel from basic repair to high-perf modifications
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Topic: Improve Fuel Economy on 360
Posted By: sctvguy1
Subject: Improve Fuel Economy on 360
Date Posted: Nov/22/2012 at 6:43pm
I have a 360, two barrel, 3sp. automatic. It is in a 1971 Matador 4 door.  The car has dual exhausts, and I was thinking of putting smaller jets in the carb, HEI ignition.  I have radial tires.  I have looked at many sites trying to find the average fuel economy of this engine/combination, but it is too old.  Are there any other things that I could do to get more miles per gallon from my car.  It is in beautiful shape, only 26K miles.  I drive very lightly.  I do not have cruise control, is it available somewhere for this model?  Thanks for any tips.



Replies:
Posted By: Buzzman72
Date Posted: Nov/22/2012 at 7:58pm
First, gearing and rpm's will have the biggest effect on your mileage...once the engine is in tune properly.

Want electronic ignition?  Why go with HEI when AMC actually used a Ford Duraspark unit from the factory, from 1978 on?  It's not THAT hard to wire up on an older 360...but then, I'm a fan of using what was factory designed to work, as long as it works well.  Take a Duraspark, add a Cap-A-Dapt setup to use the larger diameter Ford electronic cap [and the corresponding rotor], add an e-coil, and you've got as good a setup as any HEI system.

The fact that AMC never used an overdrive with the V8 is a bit of a problem.  You could swap in an AW-4 out of a 2WD Jeep with a 4.0 six, but that has its own problems...but answers can be found in the transmission section of this forum.

If the carb is properly jetted now, what do you hope to accomplish by running smaller jets?  Running an engine lean doesn't necessarily equal better efficiency [and therefore better mileage]...and may create driveability issues on top of the mileage issues you already have.

You mention having radial tires; for "ultimate" fuel economy, you should be running the tallest yet narrowest tires that will fit your car. Smaller contact patch from the tire = less friction with the road = more mileage...at a cost of a loss of handling and braking because of that same decreased road friction.  Nothing's free; it all comes at a price.

You aren't going to get anywhere near 30 MPG from a 360 in a car as heavy as a Matador.  In fact, over 20 MPG may be a pipe dream.  Decreasing the weight of the car significantly will increase your mileage, as the engine doesn't have to work nearly as hard to get the car rolling or to keep it rolling.

BUT...the biggest problem is the weight of the car, the final gearing in the top gear [rear end ratio x high-gear ratio]; and driving like you have an egg under your right foot...as well as anticipating stops, and taking your foot off the gas earlier as opposed to using the brakes as much to slow the vehicle...will have about as much effect on your mileage as anything else you can do for under $1000.  Also, doing more highway driving vs. stop-and-go city driving will make a big difference because, on the highway, you're running in the top gear for a larger percentage of your driving.

But there is no magic carb or ignition tuning specs that will dramatically change your mileage...unless your car is already in a poor state of tune to begin with.


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Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.


Posted By: 69 ambassador 390
Date Posted: Nov/22/2012 at 9:02pm
You should get 15-17 on the hwy and around 12 in the city if everything is in good shape.  better ignition will not get more MPG unless the old ignition is weak.  If you are only city driving, then you could get rid of the 2.87 rear gears and go down to 3.15 ratio.  That will help around town but hurt on the Hwy.  Alos, don't run too much pressure in those radials.  The gas mileage increase with radials comes from the flexible sidewalls and too much air makes them too stiff.  Start with about 30 psi and no more than 35.  As said before, smaller cross section tires roll better.  Like the difference between riding a mountain bike and a good road mike.  Big tires means big resistance.  Air dam in front will help keep the air out from under the car and side skirts would help too.  They would be ugly though.

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Steve Brown

Algonac, Mi.

69 Ambassador sst 390

84 Grand Wagoneer

69 Cougar XR7

65 Fairlaine 500XL

79 F-350 Super Camper Special





Posted By: Fluffy73
Date Posted: Nov/22/2012 at 9:17pm
Or just lower your expectations. A heavy car with a 6.0 liter, cast iron engine under the hood is not going to be economical. Just sayin'.  Another ignition alternative would be the Pertronix systems. Keep your stock distributor, but eliminate points. You can usually get a much more powerful coil from them as well.
 
You could also switch to a 4bbl.  I know this seems counter-intuitive but 4 barrel carbs usually have smaller primaries than straight 2-barrels.  4 barrels can give you the mix of both economy, and power when necessary.
 
Aluminum wheels can also help a little.
 
Or, invest in things like Fuel Injection, Aluminum Heads, 700R4 transmission.


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I am genetically incapable of being Politically Correct.


Posted By: FSJunkie
Date Posted: Nov/22/2012 at 9:49pm
As said, if I can average 13 MPG combined highway and city in a 4000 pound Wagoneer, you should be able to get 17 or so in that. It weighs a couple hindred pounds less with a more efficient transmission and is more aerodynamic.
 
Factory AMC axle gearing for the auto boxes tends to be pretty good all around.  The 2bbl carbs are the best fuel economy and low torqueing carbs ever made, but a slight increase in mileage can be had with a carb off a later Jeep 360.  Motorcraft made quite a few improvements to the carbs in the name of power, fuel economy, and emissions, all of which improve together.
 
The exhaust system might be too big. If they're duals, I hope they are no bigger than 2" each pipe.
 
Cold air intake in the summer, thermostatic warm air in the winter. Make sure the choke is set properly. I know my fuel mileage takes a hit in winter just because the choke is on longer.
 
Ignition timing: 5-8 degrees BTDC. Period.
 
 


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1955 Packard
1966 Marlin
1972 Wagoneer
1973 Ambassador
1977 Hornet
1982 Concord D/L
1984 Eagle Limited


Posted By: 17tamx
Date Posted: Nov/22/2012 at 10:05pm
Put the 360 in a Gremlin or 2door Hornet and pickup a few miles per gallon easy.

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Kirk P. Fletcher
70 AMX BBG w/Shadow 390 4sp
71 SC360 Wild Plum Ram Air 4sp
67 Rogue Convert 343 4sp
66 Rogue Hardtop 290 Auto
66 440 Convert 232 Auto


Posted By: dbomb
Date Posted: Nov/22/2012 at 10:50pm

We had alot of complaints about fuel economy on the grand waggoneers and j10s and 20s  when i was at the dealership. They were  pigs espescially the full time 4x4  trans case models . We had good luck advancing the timing a bit and  using water injection  as well as making sure the clutch fan was working properly as well as installing flex fans on some models . If the  EGR system is clogged or not opening it can hamper MPG espescially if youre "road timing" the ignition timing .Road timing is advancing ignition a few degrees the backing off when you hear a ping. Old carbonned up motors will ping easily as well as a disabled or malfuntioning EGR or a stuck Heat riser at the exhaust manifold . I dont know why everyone hates egr valves and disconnects them they actually can help stop detonation and allow lower octane  fuel  to be used or more lead timing to be run  while cleaning up the NOx levels emmitted .On some vehicles espesciallt like fords with a sandwich egr plate under the carb the cars and trucks were dogs with a death rattle  when the EGR plates  clogged or warped up. Later Model Grand Cherokees as well had problems  with vaccum delay valves and timing  advance  mods under AMC tech service bulletins.  Newer fords had campaigns on the 46 and 54 crown vic type intake manifolds clogging up egr. Wheel alignment can play a role as well espescially on an old car cambered out and too much toe out.



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rebuiling 73 amx need parts


Posted By: smills61074
Date Posted: Nov/22/2012 at 11:33pm
dbomb mentioned probably one of the best ideas to help with fuel economy.  A clutch fan is definitely a step in the right direction.  Should be relatively cheap.  An overdrive trans would be your best option, if there is something out there that will interchange.  If you don't drive a lot of miles.  Do the math.  The difference between 15 and 20 mpg is not much, if you only drive a thousand miles a year.  In reality, anything expensive will never pay for itself.  Good Luck and keep a light foot.

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68 Blue AMX Perfect California Body going for 401/6 speed
1 1/4 ton Power Wagon Ex Colorado Brush Truck
2006 Caddy CTS V with LS2 and manual trans Corsa Exhaust Beater car (daily driver)


Posted By: BassBoat
Date Posted: Nov/23/2012 at 8:10am

I would advise against changing the jets in the carburetor.  Leaner does not give you better mileage.  Of course, neither does richer, but the way it works is you get the best mileage when the calibration is right.  These cars tended to be tuned on the lean side for emissions to begin with, so save that for last.  EGR is particularly egregious on these old cars.  Plug it off, by disconnecting the little hose to the valve and sticking a screw or a golf tee in the hose.  Undo all the things that were done to improve emissions, all of which are at the expense of performance and efficiency.  Quicken up the advance curve with one lighter spring in the distributor, increase the initial timing with vacuum advance disconnected to 14 or 15 degrees or the most you can run and still get it to crank over and start  when hot.  You might have to limit the mechanical advance in the distributor, but that is pretty easy to do with either the brass bushing included in an advance curve kit or a piece of vacuum hose on the advance limit pin.  Some distributors actuall had two different slots, one for retarded (pun intended) US emissions and one for export.  In theory you can get too much timing, but in practice on a low compression early 70's  motor there is no such thing.  Crank it and see.  You should find that advancing the timing and running premium fuel will give you a mileage benefit beyond the increase in fuel cost.  It takes a bit of patience to fine tune everything, but do it. 

BB 


Posted By: dbomb
Date Posted: Nov/23/2012 at 10:51am
If youre looking for economy  learn to road time the engine and listen for spark nock and advance the lead timing as you go  once it knocks on accel  back off a little bit.I guess i kinda see it the other way on the EGR thing  not to get in a debate here but I know that affective EGR lowers  the peak combustion temperature and allows engine torun more lead timing  Disabling an accurate working system is actually going backwards  for an economy and performance standpoint . Just take expample of chryslers leanburn system as well as other where manifold vacuum and ported vacuum are taken and used  sycroniously to control vacuum advance  and egr function . Theres plenty of patents on it just google EGR and Ignition Timing for a better example. Nowadays theyure tuning EGR lift with Knock Sensor S ignals and boost pressure to provide best possible performance and economy. Bass Boat is right though on old cars especially like thge AMC V8 intake design its arcaic at best but still functional. Try this take an old loaded up engine with regular gas  and run like 14 to 16 degrees timing its gonna ping  a bit  then disconnect the EGR valve  it will sound like a popcorn popper till you burn a hole in a piston or break the ring lands out. ping ping ping. Im glad i got an EGR valve on my AMX . If all else fails wax the car to streamline it

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rebuiling 73 amx need parts


Posted By: FSJunkie
Date Posted: Nov/23/2012 at 9:01pm
Just because you're running as much ignition timing as you can without ping doesn't mean the engine is running at peak power and efficiency.
 
Ping is caused by the spontanious ignition of the fuel charge set off by heat and pressure. The cylinder pressure spikes rapidly and this is the sound you hear.  Since the cylinder burn event is shortened, power is reduced greatly.  Early ignition lead can raise cylinder pressures high enough to cause ping or detonation, it's technical term.  Early ignition lead creates ping in the same way preignition does, the engine doesn't know the difference.
 
It is possible to lose power through early ignition lead by another way without abnormal combustion characteristics.  In most low to moderate compression engines operating at proper temperature with proper grade fuel, detonation will not occur even with early ignition of the fuel mixture.  Cylinder pressure will gradually increase then decrease as normal without the shocking spike of detonation.  The problem with this is cylinder pressure increases high enough before the piston reaches top dead center, and tries to force the piston backwards back down the cylinder bore. The other pistons and the inertia of the rotating crankshaft assembly keep the engine turning forward, but that doesn't get around the fact that the engine is internally fighting itself. Not only that, but cylinder pressure after TDC is reduced, further lowering power output.
 
And this whole time, the engine is not pinging. In severe cases, the engine will run rough, but in mild to moderate cases, the driver is unaware.
 
The key to maximum power output is for cylinder pressure to peak at the point durring the piston stroke after TDC that the connecting rod has the most leverage on the crankshaft.  To calculate this point requires college level calculus involving the connecting rod length and piston stroke relating to the crankshaft moment arm.   For most engines with a rod to stroke ratio of 1.6:1, maximum leverage occurs around 20* ATDC.  After some more calculus and analysis of cylinder burn rates, the proper ignition lead can be determined.  That is how the engineers find it.
 
For street use, any change in engine compression ratio, intake charge temperature, fuel brand, fuel mixture, ignition system for spark intensity, etc. changes the cylinder burn rate and the required timing of the spark.  The only real way the average car owner can set their ignition timing "by ear" is by trial and error on a dragstrip or on a dyno. Without expensive test equipment to anayize cylinder burn rates, it becomes alot harder.
 
Hence why I tend to stick with stock specs for everything, as a change in one thing can throw everything else off.


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1955 Packard
1966 Marlin
1972 Wagoneer
1973 Ambassador
1977 Hornet
1982 Concord D/L
1984 Eagle Limited


Posted By: Sonic Silver
Date Posted: Nov/23/2012 at 9:45pm
Originally posted by FSJunkie FSJunkie wrote:

Just because you're running as much ignition timing as you can without ping doesn't mean the engine is running at peak power and efficiency.
 
Ping is caused by the spontanious ignition of the fuel charge set off by heat and pressure. The cylinder pressure spikes rapidly and this is the sound you hear.  Since the cylinder burn event is shortened, power is reduced greatly.  Early ignition lead can raise cylinder pressures high enough to cause ping or detonation, it's technical term.  Early ignition lead creates ping in the same way preignition does, the engine doesn't know the difference.
 
It is possible to lose power through early ignition lead by another way without abnormal combustion characteristics.  In most low to moderate compression engines operating at proper temperature with proper grade fuel, detonation will not occur even with early ignition of the fuel mixture.  Cylinder pressure will gradually increase then decrease as normal without the shocking spike of detonation.  The problem with this is cylinder pressure increases high enough before the piston reaches top dead center, and tries to force the piston backwards back down the cylinder bore. The other pistons and the inertia of the rotating crankshaft assembly keep the engine turning forward, but that doesn't get around the fact that the engine is internally fighting itself. Not only that, but cylinder pressure after TDC is reduced, further lowering power output.
 
And this whole time, the engine is not pinging. In severe cases, the engine will run rough, but in mild to moderate cases, the driver is unaware.
 
The key to maximum power output is for cylinder pressure to peak at the point durring the piston stroke after TDC that the connecting rod has the most leverage on the crankshaft.  To calculate this point requires college level calculus involving the connecting rod length and piston stroke relating to the crankshaft moment arm.   For most engines with a rod to stroke ratio of 1.6:1, maximum leverage occurs around 20* ATDC.  After some more calculus and analysis of cylinder burn rates, the proper ignition lead can be determined.  That is how the engineers find it.
 
For street use, any change in engine compression ratio, intake charge temperature, fuel brand, fuel mixture, ignition system for spark intensity, etc. changes the cylinder burn rate and the required timing of the spark.  The only real way the average car owner can set their ignition timing "by ear" is by trial and error on a dragstrip or on a dyno. Without expensive test equipment to anayize cylinder burn rates, it becomes alot harder.
 
Hence why I tend to stick with stock specs for everything, as a change in one thing can throw everything else off.
I had 2 years of college  Calculus , and don't remember enough to comment! Haha.


Posted By: smills61074
Date Posted: Nov/23/2012 at 10:11pm
     This is the first I have seen anyone mention calculus on the forum.  I am an engineer and have had calculus, physic, statics and dynamics,thermal dynamics, fluid dynamics,  etc.  You are correct about the piston firing after TDC and having the best leverage. The same with fuel combustion. 
     Factory setting are generic.  Consider them a baseline.  All engines are different.  Whether it is the carburetor, plugs, wear on the timing chain and engine, or even changes in temperature.
     I for one have always base lined my engines and then carried a timing light with me in the car.  I try adjusting the timing a degree at a time.  Once I hear pinging (usually going up a hill) I back off the timing.  Then I back off a degree at a time until I feel I have hit a sweet spot. You can do this over a few tanks of gas and get a real feeling or where your cars runs well.  You will definitely loose performance to gain a little bit of mileage.  But, there is a few miles per gallon to gain. By driving you car right an having a good tune on your car.   


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68 Blue AMX Perfect California Body going for 401/6 speed
1 1/4 ton Power Wagon Ex Colorado Brush Truck
2006 Caddy CTS V with LS2 and manual trans Corsa Exhaust Beater car (daily driver)


Posted By: purple72Gremlin
Date Posted: Nov/23/2012 at 10:38pm
Originally posted by Fluffy73 Fluffy73 wrote:

Or just lower your expectations. A heavy car with a 6.0 liter, cast iron engine under the hood is not going to be economical. Just sayin'.  Another ignition alternative would be the Pertronix systems. Keep your stock distributor, but eliminate points. You can usually get a much more powerful coil from them as well.
 
You could also switch to a 4bbl.  I know this seems counter-intuitive but 4 barrel carbs usually have smaller primaries than straight 2-barrels.  4 barrels can give you the mix of both economy, and power when necessary.
Pretty much it here...been there done that.


Posted By: purple72Gremlin
Date Posted: Nov/23/2012 at 10:50pm
Originally posted by FSJunkie FSJunkie wrote:

As said, if I can average 13 MPG combined highway and city in a 4000 pound Wagoneer, you should be able to get 17 or so in that. It weighs a couple hindred pounds less with a more efficient transmission and is more aerodynamic.
 
Factory AMC axle gearing for the auto boxes tends to be pretty good all around.  The 2bbl carbs are the best fuel economy and low torqueing carbs ever made, but a slight increase in mileage can be had with a carb off a later Jeep 360.  Motorcraft made quite a few improvements to the carbs in the name of power, fuel economy, and emissions, all of which improve together.
 
The exhaust system might be too big. If they're duals, I hope they are no bigger than 2" each pipe.
 
 
Well, I sure dont agree with what you said here...........I have put 2 1/2 inch pipes on stock engines....and its been proven that all 2 bbls were just cost cutting measures for the factories when they were not concerned with fuel economy.   (If you look under the last mid 80's V8 cars, particularly GM, and chrysler, and some Fords, you will see that the majority of the carburators are 4 bbls, why? because a 4 bbl has smaller primaries than a 2 bbl will.......and that is where fuel economy is at...........remember, the factories had to meet the 27.5 MPG average)  I will concede that the motorcraft is a good carburator, but its not a 4 bbl. and I have converted cars to a 4 bbl from a 2 bbl and the 4 bbl would average anywhere to 1-3 mpg better. and my gremlin was one of those cars too.


Posted By: purple72Gremlin
Date Posted: Nov/23/2012 at 11:03pm
Just my opinion...............advance the initial to anywhere to 8-12 BTDC.  make sure your choke opens quickly. and make sure your choke pull off is working as well. and make sure the power valve in the carburator is working.  put some good plugs and wires on it. (my preference is no champions)  get a distributor cap and rotor from blue streak. they are a set, and the cap will have copper terminals. put a vacuum gauge in the car and try to keep it above 15 inches at all times. also a tach, and try not to go over 2500 RPM.  If you do this, I believe you can increase your MPG by 1-2 MPG. 


Posted By: nda racer
Date Posted: Nov/23/2012 at 11:10pm
Originally posted by purple72Gremlin purple72Gremlin wrote:

I have converted cars to a 4 bbl from a 2 bbl and the 4 bbl would average anywhere to 1-3 mpg better...................
 
 
Just my opinion...............advance the initial to anywhere to 8-12 BTDC.  make sure your choke opens quickly. and make sure your choke pull off is working as well. and make sure the power valve in the carburator is working.  put some good plugs and wires on it. (my preference is no champions)  get a distributor cap and rotor from blue streak. they are a set, and the cap will have copper terminals. put a vacuum gauge in the car and try to keep it above 15 inches at all times. also a tach, and try not to go over 2500 RPM.  If you do this, I believe you can increase your MPG by 1-2 MPG. 
 
 
X2
 
 
 


Posted By: Buzzman72
Date Posted: Nov/24/2012 at 5:00am
I think the original premise in the original post is wrong.  You don't make an ENGINE get better mileage, unless you put it in a lighter car.  But you make a CAR get better mileage by using the steps that everyone has mentioned in this thread.

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Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.


Posted By: gwryder
Date Posted: Nov/24/2012 at 7:03am

Years ago, for a project with one of my electronics classes, I made a poor fuel economy minder. Mine used comparators, a vacuum can to turn on a red, yellow or green LEd depending on the manifold vacuum.

 A simple one can be made with a vacuum can, micro-switch and LED. The idea behind this is to have the LED turn on when the vacuum drops to the level the carb's power enrichment system comes into play (~ 8-10"Hg). I put mine on a 1980 Pontiac Phoenix and it worked really well, but was hard to drive without the LED coming on.


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John
70 AMX





Posted By: BassBoat
Date Posted: Nov/24/2012 at 8:44am
OK, let me say this another way.  Increase the timing.  No other change will make as much improvement in efficiency and driveability.  Its easy to do, costs nothing, and is readily reversible.  Advance the timing until you either do not see an additional improvement, based on your driving, your fuel, and keep advancing the timing until you observe one of these three things:  You don't see any further improvement, the car is hard to start when hot, or you get ping.  If you get ping, put in better fuel because fuel is so bad today that you will reach the limit of the fuel long before you reach the optimum conditions for driving and the increase in fuel cost will be offset by the increase in mileage. 
If you don't see an improvement, that you can feel in the seat of your pants and in your wallet, by all means put the timing back.  Tuning tip here is if it runs better retarded keep retarding it.  It won't, because in thousands of instances I have seen this happen only once, but that is how tuning works.  Try it, evaluate the result, and follow the data where it leads you.  I am a "rocket scientist", and have maybe 40 years of combustion engineering and engine development experience, and frankly could not do calculus anymore on a wager.  But recollection of calculous or ferver in conviction as exemplified above is not what you need in your case for tuning your car.  Just a little common sense and trial and error.
BB


Posted By: 73hornut
Date Posted: Nov/24/2012 at 8:51am
I would consider a high torque cam, a small 4bbl, about 350 rear gear, and an OD trans.

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71 Javelin
74 Gremlin
79 Spirit AMX
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Posted By: gtoman_us
Date Posted: Nov/24/2012 at 9:13am
Great discussion. All I know after 4 years of engineering college with calc, thermo, stats, ect. a good old fashion vacuum gauge and timing light with Petronius point replacement I keep my 65 GTO with 10:75 compression and tri power carb setup ping free. As stated earlier it takes an incremental approach to keep it street-able with today's fuel and I do have to fuss with it a couple of times a summer. I am not concerned about mileage but pre detonation even with forged pistons

I used to chart and journal what I was doing to create a base line but the fuel is so laced with ethanol over the last 4 years that the base line was invalid because I could not return to it. Cripes now I wonder what I did with the little note book?

My Pontiac owners manual requires 100 octane premium.

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Moderator - Emeritus

Used to collect trophies, now I collect gas receipts and put on miles

1964 Rambler Ambassador Cross Country Wagon
1965 GTO
1931 Model A original survivor
"Flat Roofs are Cool"


Posted By: scott
Date Posted: Nov/24/2012 at 10:12am
I'm suprised no one suggested adding a valley oil line........   Wink


Posted By: amxdreamer
Date Posted: Nov/24/2012 at 12:06pm
Originally posted by scott scott wrote:

I'm suprised no one suggested adding a valley oil line........   Wink
 
lol LOL


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Tony
Vancouver, BC
1970 AMX
1972 Badassador
AMO#10333


Posted By: dbomb
Date Posted: Nov/24/2012 at 12:11pm
what does that have to do with MPG? ohh  youre making a joke i get it now lol

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rebuiling 73 amx need parts


Posted By: dbomb
Date Posted: Nov/24/2012 at 12:32pm
SCTVGUY1 before go getting into rod length ratios and combustion dwell and hemispherical vs wedge head desisn and burn characteristics or the  ability to convert into brown gas burning you might just wnna look into a simple water injection system . JC Whitney and Sears and others used to sell alot of them and i can tell you that i installed more than a few of them at the Jeep dealership on grand wagonners and big jeeps in the past . If you just google water injection for cars it will tell ya  all about it. Maybe im an old fart at 46 but i used to work on cars with carbs and points  as well as todays newer injected supercharged  or turbo aspirated vehicles. Keep it simple as your car is  simple . You dont need one of those $400 dollar kits either  $50 old style kits just had a water bag  and a vacuum T to plug into ported vacuum[port above throttle plate] and would use vacuum to draw in water or widshield washer solvent. We did ALOT of these in the past and could run @16 degrees advance without problems  on stock motors and the extra lead timing really woke up the motor and made more efficient. Supposed to be a new spark plug design coming out tht I heard is gonna be relevant as well not just Splitfyre hype.

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rebuiling 73 amx need parts


Posted By: purple72Gremlin
Date Posted: Nov/24/2012 at 4:06pm
Also, stock specs are just a baseline.  when an engine has miles on it, the engines requirements changes, (For example, the timing chain will stretch and retard the timing, once it does that then stock specs go out the window)...............So, you have to advance the timing..............


Posted By: Charles Smiley
Date Posted: Nov/24/2012 at 4:51pm
With such low mileage on a car that old it begs the question... How much would you really save on total fuel cost anyhow? Whatever you spend has to have a payoff point in the near future to justify the costs.
 
With the crappy "green" fuel they have here in the People's Republic of Kalifornia, I've had to increase the jetting on my 401 just to keep it from pinging. And I already have done a lot to make it more efficient, electronic ignition, headers, carb, intake, cam selection etc...


Posted By: bigbad69
Date Posted: Nov/24/2012 at 6:08pm
Originally posted by gwryder gwryder wrote:

Years ago, for a project with one of my electronics classes, I made a poor fuel economy minder. Mine used comparators, a vacuum can to turn on a red, yellow or green LEd depending on the manifold vacuum.

 A simple one can be made with a vacuum can, micro-switch and LED. The idea behind this is to have the LED turn on when the vacuum drops to the level the carb's power enrichment system comes into play (~ 8-10"Hg). I put mine on a 1980 Pontiac Phoenix and it worked really well, but was hard to drive without the LED coming on.
My old 82 Caprice had a simple vacuum gauge as a fuel economy meter - no LED, just an analogue sweep. If I kept the needle at max as much as possible, the vehicle's fuel mileage went up.


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69 Javelin SST BBO 390 T10


Posted By: bigbad69
Date Posted: Nov/24/2012 at 6:09pm
Originally posted by gtoman_us gtoman_us wrote:

My Pontiac owners manual requires 100 octane premium.
What octane does the car require? Smile


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69 Javelin SST BBO 390 T10


Posted By: FASTNASH
Date Posted: Nov/25/2012 at 7:19am
What is your driving habits if it's full thottle and stop. That won't help either? Depending what ever do to engine or fuel delivery? How drive the car has lot ot do with it. Would like to know what is very day car is because what ever person have that car like 4 cyl, that 360 can feel rocket ship that won't help either, Because love feel of that power and dual exhaust could make your gas MPG go down. Had people this year at shows said i don't get any gas MPG. See how leave show field and pull out from ever stop. Then you go that's why they don't any MPG. Fun factor comes in? So cost money like everything else.

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AMO#3040 NAMDRA#1115 AMC's are just like potato chips you just can't have one.              


Posted By: gwryder
Date Posted: Nov/25/2012 at 7:36am
Originally posted by bigbad69 bigbad69 wrote:

Originally posted by gwryder gwryder wrote:

Years ago, for a project with one of my electronics classes, I made a poor fuel economy minder. Mine used comparators, a vacuum can to turn on a red, yellow or green LEd depending on the manifold vacuum.

 A simple one can be made with a vacuum can, micro-switch and LED. The idea behind this is to have the LED turn on when the vacuum drops to the level the carb's power enrichment system comes into play (~ 8-10"Hg). I put mine on a 1980 Pontiac Phoenix and it worked really well, but was hard to drive without the LED coming on.
My old 82 Caprice had a simple vacuum gauge as a fuel economy meter - no LED, just an analogue sweep. If I kept the needle at max as much as possible, the vehicle's fuel mileage went up.

I found that out too. Driver technique is the best improvement in fuel economy one can make. Add that to some of the techniques talked about here and fuel mileage has got to increase dramatically. Too bad it's the least amount of fun.

Basically, driving by a vacuum gauge is the same thing. Using a light throttle and drive by highest vacuum, one can achieve respectable mileage. My Silverado with the 5.3 and 6 speed auto averages 18.7 mpg. I drive lite and mostly rural driving, so driving technique and minimum stops makes a big difference.


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John
70 AMX





Posted By: tsanchez
Date Posted: Nov/25/2012 at 8:40am
Best way to increase mileage is to cheat when doing the calculation, its what most guys do when the want to brag about how good their tune is.

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Posted By: nda racer
Date Posted: Nov/25/2012 at 9:50am
Originally posted by tsanchez tsanchez wrote:

Best way to increase mileage is to cheat when doing the calculation, its what most guys do when the want to brag about how good their tune is.
 
Yep, everybody gets 20+ mpg till you go cruising with them. Or change your rear gear ratio from 2.87s to 3.54s and not change the speedo gear to match.


Posted By: smills61074
Date Posted: Nov/25/2012 at 10:22am
I definitely agree with mileage being linked to driver habits.  I have a 1993 Cadillac Deville.  It has a instant MPG gauge as well as total MPG.  It definitely teaches you to have a light foot.  Although it is electronic, I assume the instantaneous works off vacuum.  You can see what happens when you leave a stop sign with your foot down, or ease away from a stop sign with a light foot.  I have filled the fuel tank until I can't put anymore in (full up to the neck).  Then I have driven a tank full and refilled it the same way.  This is how to accurately check your mileage.  Believe it, or not, the gauge on the Cadillac is right on.  The car has 230,000 miles on it.  I just drove 1200 miles to Nashville and back.  I averaged 24.5 miles per gallon overall.  In Nashville, I put a can of Seafoam in the Cadillac and a right hand drive Subaru that we picked up for my wife's mail route.  We had to stop about every 275 miles to fill my wife's Subaru up.  The last tank, I actually used less fuel than the Subaru.  The Subaru got 27.3 mpg and the Cadillac was right at 28.  Each had been filled up to the neck each time.  Not bad for a V8.  Cadillac's are deceiving.  The car has plastic fenders, aluminum heads and only weighs around 3600 lbs.  But a light foot is the trick.  So, driving habits play a big role no matter what you are driving.    

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68 Blue AMX Perfect California Body going for 401/6 speed
1 1/4 ton Power Wagon Ex Colorado Brush Truck
2006 Caddy CTS V with LS2 and manual trans Corsa Exhaust Beater car (daily driver)


Posted By: Charles Smiley
Date Posted: Nov/25/2012 at 11:04am
I always blamed the mileage drop on them sitting in the other seat and adding too much extra weight.


Posted By: Charles Smiley
Date Posted: Nov/25/2012 at 11:11am
I have a '83 Jeep J10 with a 360/auto and Selectrac. On a few trips from LA to Contra Costa county I nursed the throttle (visualizing a vacuum gage) and I got 17.7 mpg. That was with a load of car parts and a passenger. I kept the rpms at 2500, or below, and that was a little over 55-mph. I consider that a record. Any faster and the mileage would plummet.


Posted By: gwryder
Date Posted: Nov/25/2012 at 2:11pm
I'm not sure if the cheating comment was directed at me, but below is from my Silverado's display of average fuel mileage and how many gallons the average is calculated over. The last photo is my log book. The first calculation is ~19.7 and the last is ~16.5. The latter is probably due to the weather getting colder up here.
 
 
 


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John
70 AMX





Posted By: Class Guy
Date Posted: Nov/26/2012 at 8:56am
All kinds of good, basic information in this thread.  Some additional perspectives I would add:
1.  It's not just the amount of initial timing that counts.  The ignition advance curve is also critical.  Total advance, rate of advance and the adding of vacuum are all important.
2.  Such exercises take lots of testing which requires lots of record keeping.  You must have some test procedure that is repeatable.  I once did an exercise with an '85 GMC 3/4T Suburban with a 454 because when I bought it, the best it would do was about 10 mpg empty.  It would suck down to about 5 1/2 mpg pulling a 7500 lb trailer!  Since I was also using it to commute about 80 miles a day to work, it gave me an excellent test environment.  Doing nothing more than carb and distributor tweaks along with disabling two smog pumps (!) and the heat riser, the mileage increased to a best of 14.84 mpg (14.5 avg) and 10.5 pulling the trailer.  It took six months of testing.
3.  The 360 has a poor combustion chamber/piston top design for efficiency.  You will not achieve the same level of performance as some other engine designs.  It would be nice to have a good combustion chamber and a piston top with some quench.
4.  Keep in mind that the suggestion for changing to a 4-bbl will also require changing the manifold.  The 2-bbl manifolds have a smaller port cross section than the 4-bbl, so you willl sacrifice some velocity at low engine speeds with a 4 bbl manifold.  That means that the carb selection is important to provide the best fuel atomization.  I have found that no carb beats a Quadrajet for that level of efficiency.  Putting a Qjet on an AMC has its own challenges (not the least is the ridicule from the Forum), but I would suspect it to yield the best performance.  I would select an Edelbrock Performer as the manifold to start with regardless of carb choice.  It has the best cylinder-to-cylinder distribution of any manifold.  Incidentally, the reason for the factories spending so much effort on optimizing the 4bbl carbs during the 1980s was economic as much as performance.  All the engines had to pass smog requirements and it was much cheaper to concentrate on one venue rather than spend $$ on a 4bbl and 2bbl applications.  We all benefitted, however, with some good designs to work with.
5. Lower engine speeds is a given to increased mileage.  Although it is expensive, a swap to a GM 700R4 is a good choice.  A 200R4 is better because it doesn't require the electronic controls, but not as plentiful.  GM used 2.29 & 2.41 rear gears with .73 & .63 overdrives in the 80s to do 20+ MPG in their barges.
6.  You will not be able to stand back and simply throw parts at the car to achieve what you want.  It will take some education, understanding of mechanics and lots of work.  It is a rewarding and fun exercise though.



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