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  #1  
Old 01-15-2013, 08:35 PM
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Tinkerjeep Tinkerjeep is offline
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The Emission vs. Mileage vs. Power...

Did some studying, read up a bunch on Holleys, and the book is chock full of general mileage / performance stuff!

The book: "Holley Carburetors and Manifolds", by Mike Urich and Bill fisher.

Where to start...

Well, the book highlights Holley carbs and Manifolds and then goes on to address the history of emission tuning (detuning) that the OEMs did in the 1970s and then the rise of engines that actually made power, mileage and emitted fewer pollutants. Generally:

Ignition timing...at the beginning of the "smog era" advance curves were tuned to make better efficiency and power...and were generally more advanced than they were a few years later when OEMs started retarding advance curves to reduce efficiency to reduce exhaust temps, which reduced HC and NOx.

Compression Ratio...Higher CR ensures better efficiency, and power, but also makes more pollutants and requires higher octane fuel. Higher compression ratio requires less ignition advance.
The OEMs dropped CR in the early 1970s to reduce pollutants.

Leaded Fuels...Leaded Fuel requires MORE advance to ignite.
The OEMs were required to build engines that would run on UNLEADED fuel in order to remove lead from the polutants and...to accomodate the new Catalytic Convertors to be fitted on all vehicles beginning in 1975. (Except for trucks...they all got Cats in 1979)

Catalytic convertors - introduced in '75...designed to convert CO into CO2, HC into H2O and CO2, and NOx into Nitrogen. Cats require high exhaust temps to light off the catylization. They do not work with leaded fuels.

EGR...EGR recirculates exhaust gas back into the intake manifold to dilute fresh air/fuel charge so to DE-EFFICIENTIZE the burning of the mixture in the chamber. This cools the combustion temp. Cooler combustion temp means cooler exhaust temp, which meant less NOx production.

CAMSHAFT EGR can also be implemented with large overlap cam shaft profile in a street driven car. It acts just like a lopey race cam -crappy idle, because exhaust gases are flowing back into the cylinder as it is filling with air/fuel charge. It runs like crap until the right RPM is reached and then it makes power...

THE ABOVE REASON is EXACTLY WHY 401s SUCKED! The camshaft profile in the 401s was WAY different than the 360 cam profile. Look it up in a 1975-1978 Jeep TSMs...they are a single pattern cam, but with 61* of overlap!!! Great for racing at high RPM...but the 401 in the trucks never revved high enough to reach that point. Maybe the Cam would work better in a built up race 401...but Desktop Dyno didn't really indicate this. I only tried it in a mildly built street 401...but it was only good for 370 hp and 370 torque. Edelbrock Performer cam in same motor was good for about 350 hp and 450 torque and had much better low - mid RPM drivability.

LOWER Gear Ratio...in the axles of course...this is obvious, the lower RPM the engine has to turn to make the vehicle attain the national 55mph speed limit in the 1970s and 1980s, the less total exhaust is emitted from the tail-pipe.


So what can we learn from all this?
Well, due to unleaded gasoline requirements for Catalytic convertors, the ignition in later engines can be decreased. But the larger chambers and lower CR means you need to increase the ignition advance. So you effectively cancel any change from normal.

Further...Due to Catalytic convertors the CR could be raised, and this would allow more efficiency and power. Unfortunately AMC never got in on this...8.3:1 ratio in 360 engines to the very end. So the 360 was rated at less power output than the 258 I-6 motor. The 258 went on to be the 4.0 liter which made more power and got better mileage...and I believe had a higher CR in later years.

Recommendations:
If legal...

EGR intake - the EGR is not any kind of performance equipment, it is simply there to dilute air/fuel charge. It will make the engine less efficient and produce less power. Edelbrock makes a good dual-plane...Holley makes the Holley 300-31Z, a single plane, low rise intake with balance tube. This is supposedly a really well engineered intake, increase low RPM drivability over a normal single plane, but increases power production in the high rpm range , where a normal dual-plane is weaker. it does have provision for EGR. block it off.

Exhaust- rip off the stupid air-injection crap and port the manifolds...I'm talking 1975-1979 manifolds because 1980 and newer exhaust manifolds are junk due to the driver-side log-style - just get long-tube headers for this.
The ported 1975-1979 Jeep mainfolds are good flowing, they outflow Shortie headers in many cases. But long tube headers are better. Run Dual pipes and free flowing mufflers.

Catalytic convertor...lose it. The stock cats were nothing good for performance very restrictive to flow. If you want to run an aftermarket Cat, I'd suggest a really free flowing set of smaller cats, mounted really close to the header collectors. The problem with this is you need to heat-shield the hell out of these to avoid grass-fires off-road, and the Cats require really finicky tuning...really hard to do with a carb and standard ignition.

CamShaft (401)...pull that stupid drag-race style bump-stick outta there and dump it in the recycler bin. Use a 360 camshaft or an aftermarket cam set up for good Truck performance. Don't go too big...the Jeep is not a race car weighing 2,000 pounds. FEW guys can and do run race motors in a 4600 pound Jeep. Install a good cam with very little overlap (if any) for good low RPM torque...the headers will raise this somewhat allowing good mid-range and high range power.

Compression Ratio...RAISE IT! you can mill your heads and deck the block to get pretty close to 9.5:1 and higher. Using most performance 360-401 pistons you can select less dish, but Domed pistons actually have a few problems, Domed pistons are not as good for side-thrust issues and a few other things I've forgotten. I've only dealt with this on a limited level. Also, aluminum heads can take about another point of CR than Iron heads using 91-92 octane.

Carb...lose the Motorcraft 4350. When you buy a manifold (do not use a 4-barrel carb on a 2-barrel intake...or a square-bore-to-spread-bore adapter, it screws your flow) get a decent emmission/street performance 4-barrel carb. Holley 4180s and some 4160/4150s in the 500-600 cfm range are a good choice. (If you like Holleys). I prefer Edelbrock/Carter carbs for obvious reasons, (Same cfm) though they tend to be slightly less tunable. You might think a 2-barrel carb is better for mileage. No, it simply limits power output in the higher RPM range. You can get a Holley 2300 500CFM 2-barrel, but its not gonna be set up for good lower rpm drivability. The cool part of a street 4-barrel - the primary side can have smaller primary venturis/bores to work well in low-mid RPM, then when you need to pass the dork in front of you doing 15 under the posted, you mash the loud pedal and you have a whole other 2-barrel carb to furnish you with more fuel/air volume at higher RPM! Best of both worlds.

Ignition Timing...depending on what you end up doing, you may need more or less ignition timing than the stock distributor came with. The cool thing is -they are somewhat interchangeable and tunable. You have alot of curves and distributors to choose from starting in 1970 with the 360 (or earlier if you count the 290,343,390) up to1991 with the last 360.

Any questions?

Last edited by Tinkerjeep : 01-15-2013 at 08:41 PM.
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  #2  
Old 01-15-2013, 09:06 PM
Blake Blake is offline
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Nowhere did you mention TBI
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  #3  
Old 01-15-2013, 09:13 PM
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Tinkerjeep Tinkerjeep is offline
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Quote:
Originally Posted by Blake
Nowhere did you mention TBI

I'm not going to recommend TBI...I have no experience with it, its not stock or designed for an AMC engine. And mileage improvement and horsepower gains are not a sure thing. About the same mileage and power as a well-tuned carb on a 401 is what others here with TBI have posted.

Do you have better numbers?
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Old 01-16-2013, 12:23 PM
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rreed rreed is offline
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Don't forget the hot ignition vs. stock. Hahaha!
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  #5  
Old 01-16-2013, 01:56 PM
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EGR can actually increase engine efficiency and MPG while lowering emissions.
It can allow some engines to run MORE initial advance.
Removal of the EGR will have zero effect on performance.
The engine may actual perform worse without it depending on the tune.

It's proven on computer controlled engines.
On a Ford Mustang 5.0 injected engine leaving the EGR enabled can result in 1-2MPG increase vs. simply turning it off.
A very well known tuner told me this, and I tried it.
He was 100% correct.

On my '88 GW when it was still carb'd I could run more initial advance with the EGR.
If I disconnected it, and left the timing alone the engine would ping.

Opinions vary, I leave them installed and working.

I rip off the air injection stuff, and all the additional useless vacuum lines/devices though.
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  #6  
Old 01-16-2013, 03:41 PM
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FSJunkie FSJunkie is offline
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Last edited by FSJunkie : 01-16-2013 at 05:40 PM.
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  #7  
Old 01-16-2013, 05:12 PM
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fulsizjeep fulsizjeep is offline
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Quote:
CAMSHAFT EGR can also be implemented with large overlap cam shaft profile in a street driven car. It acts just like a lopey race cam -crappy idle, because exhaust gases are flowing back into the cylinder as it is filling with air/fuel charge. It runs like crap until the right RPM is reached and then it makes power...

THE ABOVE REASON is EXACTLY WHY 401s SUCKED! The camshaft profile in the 401s was WAY different than the 360 cam profile. Look it up in a 1975-1978 Jeep TSMs...they are a single pattern cam, but with 61* of overlap!!! Great for racing at high RPM...but the 401 in the trucks never revved high enough to reach that point. Maybe the Cam would work better in a built up race 401...but Desktop Dyno didn't really indicate this. I only tried it in a mildly built street 401...but it was only good for 370 hp and 370 torque. Edelbrock Performer cam in same motor was good for about 350 hp and 450 torque and had much better low - mid RPM drivability.
REALLY? It has been my impression that 360 and 401 cams were the same from the factory. This may be up for debate but not from me.
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  #8  
Old 01-17-2013, 04:39 PM
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Tinkerjeep Tinkerjeep is offline
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Quote:
Originally Posted by fulsizjeep
REALLY? It has been my impression that 360 and 401 cams were the same from the factory. This may be up for debate but not from me.

Nope. Look in the 78 TSM.
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  #9  
Old 01-17-2013, 04:50 PM
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Tinkerjeep Tinkerjeep is offline
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Quote:
Originally Posted by babywag
EGR can actually increase engine efficiency and MPG while lowering emissions.
It can allow some engines to run MORE initial advance.
Removal of the EGR will have zero effect on performance.
The engine may actual perform worse without it depending on the tune.

It's proven on computer controlled engines.
On a Ford Mustang 5.0 injected engine leaving the EGR enabled can result in 1-2MPG increase vs. simply turning it off.
A very well known tuner told me this, and I tried it.
He was 100% correct.

Your statements here are EXACTLY why this myth keeps perpetuating. YOU ARE RUNNING A COMPUTER CONTROLLED VEHICLE!!!

No FSJ has a computer on it! Maybe a spark control box...and maybe an elecric carb, but no brain-box, no TBI.



Quote:
Originally Posted by babywag
On my '88 GW when it was still carb'd I could run more initial advance with the EGR.
If I disconnected it, and left the timing alone the engine would ping.

Your "I can run MORE ADVANCE!" statement is exactly the WRONG idea. You do NOT want to run more advance. You want to get efficient, quick ignition and even burn, with NO exhaust reintroduced to drop exhaust heat. Lowering exhaust temp is the ONLY reason EGR was introduced. Its ONLY reason is to drop emissions of NOx. That's it. With EGR, YOU NEED to run more advance in order to ignite the charge. Same thing with lower CR, more quench (in the 360), larger volume combustion Chambers, and Leaded gas. ALL of the above REQUIRES the ignition advance to increase.

Quote:
Originally Posted by babywag
Opinions vary, I leave them installed and working.

Opinions vary, but facts do not.


Quote:
Originally Posted by babywag
I rip off the air injection stuff, and all the additional useless vacuum lines/devices though.

If you remove part of the system, remove it all. its pretty much tuned to work together...its like upgrading for more horsepower by putting a drag racing cam in the motor and changing nothing else.
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Old 01-17-2013, 04:53 PM
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Tinkerjeep Tinkerjeep is offline
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Quote:
Originally Posted by rreed
Don't forget the hot ignition vs. stock. Hahaha!

HEI was intended to ignite a leaner mixture with a larger plug-gap. the larger gap exposes more fuel/air mix to the spark kernal. the larger gap make more resistance, therefor the higher voltage of the HEI is needed to ensure ignition.
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  #11  
Old 01-17-2013, 06:28 PM
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babywag babywag is offline
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Quote:
Originally Posted by Tinkerjeep
Your statements here are EXACTLY why this myth keeps perpetuating. YOU ARE RUNNING A COMPUTER CONTROLLED VEHICLE!!!

No FSJ has a computer on it! Maybe a spark control box...and maybe an elecric carb, but no brain-box, no TBI.





Your "I can run MORE ADVANCE!" statement is exactly the WRONG idea. You do NOT want to run more advance. You want to get efficient, quick ignition and even burn, with NO exhaust reintroduced to drop exhaust heat. Lowering exhaust temp is the ONLY reason EGR was introduced. Its ONLY reason is to drop emissions of NOx. That's it. With EGR, YOU NEED to run more advance in order to ignite the charge. Same thing with lower CR, more quench (in the 360), larger volume combustion Chambers, and Leaded gas. ALL of the above REQUIRES the ignition advance to increase.



Opinions vary, but facts do not.




If you remove part of the system, remove it all. its pretty much tuned to work together...its like upgrading for more horsepower by putting a drag racing cam in the motor and changing nothing else.

LOL welcome to the year 2013.
Both my Jeeps are fuel injected, and both get better mileage and power vs. stock MC2150.

I'm done here you obviously are too stubborn to learn anthing new.
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  #12  
Old 01-18-2013, 09:56 PM
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cjarcher cjarcher is offline
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Quote:
Originally Posted by Tinkerjeep
Your statements here are EXACTLY why this myth keeps perpetuating. YOU ARE RUNNING A COMPUTER CONTROLLED VEHICLE!!!

No FSJ has a computer on it! Maybe a spark control box...and maybe an elecric carb, but no brain-box, no TBI.





Your "I can run MORE ADVANCE!" statement is exactly the WRONG idea. You do NOT want to run more advance. You want to get efficient, quick ignition and even burn, with NO exhaust reintroduced to drop exhaust heat. Lowering exhaust temp is the ONLY reason EGR was introduced. Its ONLY reason is to drop emissions of NOx. That's it. With EGR, YOU NEED to run more advance in order to ignite the charge. Same thing with lower CR, more quench (in the 360), larger volume combustion Chambers, and Leaded gas. ALL of the above REQUIRES the ignition advance to increase.



Opinions vary, but facts do not.




If you remove part of the system, remove it all. its pretty much tuned to work together...its like upgrading for more horsepower by putting a drag racing cam in the motor and changing nothing else.

Alot of full size jeeps had computers. The computer on my '82 controls/modifies: carburetor mixture, ignition advance, air pump system, and idle speed via solvac.
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  #13  
Old 01-18-2013, 10:43 PM
Blake Blake is offline
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Quote:
Originally Posted by cjarcher
Alot of full size jeeps had computers. The computer on my '82 controls/modifies: carburetor mixture, ignition advance, air pump system, and idle speed via solvac.

Exactly what computer are you referring too?

The only electronic devices are the ignition and the cruise control. Have I missed something? At least that's all I remember removing when I converted all my FSJ's to TBI. Maybe the little blue chime box? (Flint )
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Old 01-19-2013, 12:07 AM
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austinaubinoe austinaubinoe is offline
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80+ 4.2's had computer controlled carter carbs.

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Old 01-19-2013, 12:56 AM
Blake Blake is offline
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Oh right. They did.

All of mine are V8's
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Old 01-19-2013, 11:13 AM
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Everyone hates on the carter BBD... sad.
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Old 01-19-2013, 06:54 PM
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Quote:
Originally Posted by babywag
EGR can actually increase engine efficiency and MPG while lowering emissions.
It can allow some engines to run MORE initial advance.
Removal of the EGR will have zero effect on performance.
The engine may actual perform worse without it depending on the tune.
....
On my '88 GW when it was still carb'd I could run more initial advance with the EGR.
If I disconnected it, and left the timing alone the engine would ping.

Opinions vary, I leave them installed and working.

I rip off the air injection stuff, and all the additional useless vacuum lines/devices though.

X2..(except I'm not qualified to discuss computer controlled engines.)

Hate to take sides when two serious & competent people debate...BUT, I did take the time to experiment with this specifically to confirm the matter or bust the myth. At least for myself. If after tweaking timing this way or that I had been able to figure out a way to make my 360 perform better withOUT EGR then I'd say so and be promoting that and report exactly what I did for the benefit of others. But the opposite turned out to be true. So I put the EGR back on, tweaked the timing back to what it wanted and all is well.

Ultimately all I did was to confirm exactly what certain write-ups say about EGR, the bottom line of which is: Its OK..works fine....does not adversely impact power & efficiency. I was aware of this going in, but I suffer from the same phenomenon as do many others: "You don't understand...I'm different!"

Disclaimer: Certain early engines on which EGR was a slap-on instead of a design-in thing DID have performance and mileage issues compared to EGR being disabled. (I was there when it happened) And 35-40 years later the myth still survives that its bad stuff.

Otherwise, ditto on the vacuum lines. I'm totally CTO-less and AIR-less. I now only have dizzy, EGR and air cleaner outer door vacuum lines.

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Old 01-20-2013, 01:56 PM
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Quote:
Originally Posted by cjarcher
Everyone hates on the carter BBD... sad.

Not me. I just don't like the computer controlled version
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Old 01-20-2013, 02:06 PM
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Yeah it seems just as good/bad as every other aluminum bodied carb of the '80's.. so it's aweful, but in the same way that a mc2150 is aweful. At least my in my somewhat idiosyncratic head..
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Old 01-20-2013, 04:18 PM
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Mr. Goatman Mr. Goatman is offline
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Quote:
Originally Posted by Rich88
X2..(except I'm not qualified to discuss computer controlled engines.)

Hate to take sides when two serious & competent people debate...BUT, I did take the time to experiment with this specifically to confirm the matter or bust the myth. At least for myself. If after tweaking timing this way or that I had been able to figure out a way to make my 360 perform better withOUT EGR then I'd say so and be promoting that and report exactly what I did for the benefit of others. But the opposite turned out to be true. So I put the EGR back on, tweaked the timing back to what it wanted and all is well.

Ultimately all I did was to confirm exactly what certain write-ups say about EGR, the bottom line of which is: Its OK..works fine....does not adversely impact power & efficiency. I was aware of this going in, but I suffer from the same phenomenon as do many others: "You don't understand...I'm different!"

Disclaimer: Certain early engines on which EGR was a slap-on instead of a design-in thing DID have performance and mileage issues compared to EGR being disabled. (I was there when it happened) And 35-40 years later the myth still survives that its bad stuff.

Otherwise, ditto on the vacuum lines. I'm totally CTO-less and AIR-less. I now only have dizzy, EGR and air cleaner outer door vacuum lines.


First let me say I know nothing about this. The above reference about early engines having performance and mileage issues.... was there a change in the AMC engines? I have rebuilt mine and it's a bit like the Johnny Cash car... a bit from this year and that. I was unaware of any big changes.
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