Re: IML: Lean Burn (was: 440 compression??)

[Christopher H <imperial67@xxxxxxxxxxxxx>]

Title: Re: IML: Lean Burn (was: 440 compression??)

Not all Lean Burn cars have the label on the air cleaner. Only 440s so equipped have a “pie pan” insert label proclaiming “ELECTRONIC LEAN BURN.” However, all ELB cars do have a rectangular “box” protruding from the side of the air cleaner, and the box came with a silver metal plate on top with orange and black lettering reading “Spark Control Computer” or something to that effect. If you have a plain round air cleaner cover with only a snorkel on it, you do not have ELB.

ELB was a decent and fairly simple system and allowed Chryslers to pass emissions on regular gas through 1977 (all 1978 cars use unleaded). I feel it’s been unfairly maligned by mechanics too lazy to figure out how it should work, or who found it easiest to blame it for every drivability problem an owner encountered. It’s not really an engine management computer (in the modern sense) but really just an electronic substitution for the timing advance mechanism common to most distributors. It alters spark timing (nothing else) based on input from various sensors (I believe a total of six) such as coolant temperature, engine rpm, etc., and allows essentially an infinite number of profiles to the spark advance curves based on actual driving conditions at the moment. A conventional distributor only has one curve (the curve is the shape of the graph when you plot the number of degrees of timing advance versus rpm), so it’s a compromise. The ability to adjust timing so precisely allows the engine to run well on a leaner carburetor mixture under certain circumstances than would be possible with a single timing curve.

My ‘78 NYB has its original system 100% intact and it is 100% functional. The car even passes California’s biennial Smog Check like a new car, even though the 400 V8 in my car was not available new in CA because it failed to meet emissions standards. I’m a believer.

ELB was less common in Canada, but if the car was born with it, removing it is neither the only solution nor necessarily the best solution. It’s most often just an easy scapegoat for other problems or just insufficient diagnosis, which is spelled out very well in the Electrical Section of the FSM.

Chris in LA
78 NYB Salon
67 Crown


On 11/29/06 2:41 PM, sosmi@xxxxxxxxxxx at sosmi@xxxxxxxxxxx wrote:

> Andrew,A lean-burn motor has a engine management computer, mounted on the air cleaner assembly, (with lots of wires) and Chrysler Proudly announced it on the top of the filter housing.I think this GEM came around 74-75. I had one on my 78 NYB. I removed it, and used a 74 NY engine harness, distributor, and coil and ballast resistor. As far as headers go, I would never put headers on something like an Imp, or NY'er. That's my opinion, however the dual exhaust works great.You may find the manifold(s) are cracked, about in the center, (been there had that), in which case headers are an option Although I don't know what would fit, without the HEAT TO BEAT TO FIT procedure.Ya'll have a nice day, Dave.
>  
> > -------------- Original message -------------- 
> > From: "Andrew A." <canafornia@xxxxxxxxxxxx> 
> > I'm not planning to touch the internals of my engine for a while as it runs super smooth, is low mileage, and I just have way too many more pressing projects to warrant having still another motor sitting on an engine stand in the garage...This winter it willl be bodywork and paint which includes redoing the vinyl top..I have to take the exhaust manifolds off as it does have a major exhaust gasket leak on the left side and so am planning to go to dual exhaust and flowmasters at the same time..I figure I'm paying for the gas so I wanna hear it burn! ;-)...Are there any headers available for this year or should I just leave the manifolds as they are?..
> > What exactly was a LEAN BURN car? how can you tell?  and how do you remove it?...I have a Canadian car, so I don't know if that was an option up here or not
> > > ----- Original Message ----- 
> > > From: sosmi@xxxxxxxxxxx 
> > > To: mailing-list@xxxxxxxxxxxxxxxx 
> > > Sent: Wednesday, November 29, 2006 11:22 AM
> > > Subject: Re: IML: 440 compression??
> > >
> > > It sounds like you have a healthy engine, but as far as raising compression, I think you can get the performance improvements, without messing with the engine too much.I'm not sure if you have a"LEAN-BURN" motor, but if you do, that goes first. Next a dual exhaust system, I had a78 NYB, I used 69 440 RoadRunner mufflers with 21/4 inch tail pipes.Then a little carb mods.We went 1 step further, and changed the rear axle ratio to 3.55 .It wasn't a rocket-ship,but it sure ran good, and could still get 13-15 mpg.Raising the compression on your engine won't help much, unless you change the cam, carb, and do the above. Don't forget what your driving.Ya'll have a nice day, Dave.
> > > > -------------- Original message -------------- 
> > > > From: "Andrew A." <canafornia@xxxxxxxxxxxx> 
> > > > great thanks!..I figured it was about normal as all cylinders are within 5PSI of each other and the motor runs smooth as silk but I just figured I would check with those "in the know".....What needs to be done to raise the compresion to the level of the high perf. 440's?..is it just the heads that are different or are the pistons also different from my 1975  as compared to the late 60's 440's?....Also how much more power should that give me?...
> > > > > ----- Original Message ----- 
> > > > > From: DR CHALLENGER <mailto:drchallenger@xxxxxxxxxxx>  
> > > > > To: mailing-list@xxxxxxxxxxxxxxxx 
> > > > > Sent: Tuesday, November 28, 2006 12:14 AM
> > > > > Subject: Re: IML: 440 compression??
> > > > >
> > > > > compession ratio was rated a 8.2 to 1, but its more like 7.7 or so. 125 PSI 
> > > > > sounds normal.
> > > > > .
> > > > >
> > > > >
> > > > > >From: "Andrew A." <canafornia@xxxxxxxxxxxx>
> > > > > >>Just wondering if anyone knows off hand what the normal good cylinder 
> > > > > >>compression PSI is for a 1975 440?...Usually I'm used to V8's being in the 
> > > > > >>145-160 range, but all my cylinders in my 1975 440 are between 122-128..I 
> > > > > >>understand that these are low compression engines but have no idea what is 
> > > > > >>considered "low compression"...Is that normal for these engines?
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > >
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