Converted from Lean Burn

[ArtH]

I have removed all the of the lean burn ignition system and I'm getting the timing sorted out. I'm thinking 10 degrees BTDC with no vacuum advance and "all in" at about 32 ~ 35 degrees.

I'm sure others have already made this conversion, so I'd appreciate advise rather than having to reinvent the wheel. Thanks.

 

[LS-300]

Best explanation in my opinion: http://www.imperialclub.com/Repair/Electrical/Electronic/index.htm

 

[ArtH]

Thanks. That's what I was looking for.

 

[306Doba]

I just realized a couple weeks ago that at some point in my cars life the lean burn computed had been bypassed. Anyone know what kind of hp/tq the car should be making? (360 motor) not that important really as I drive the car like a granny, just curious. I was actually supprised to discover that because the car gets amazing highway mileage, drove 1800 kms (fully loaded with gear) on 2 1/4 tanks of gas. The drive included going all the way through the rockies too.

 

[ArtH]

http://www.moparautos.com/cordoba75-77.htm

The above link has some specs. For 1976 it was said to be 170 hp @ 4000 rpm. I rough computed your fuel consumption at 20 mpg assuming you have a 25 gallon gas tank that I believe they were all equipped with. That's not bad for a large car from the mid to late 70's. HP figures after about 1971 +/- are lower for a couple reasons than earlier numbers you will see posted. First off, they used a different system of rating engine hp. They did it with all accessories mounted to offer more realistic ratings. Secondly, engines were "detuned" to meet EPA requirements to reduce emissions. One of the major HP losses was due to dropping compression ratios. Engines that were once up to 10:1 or higher were dropped to 8.5:1 or even 8.2:1. Valve timing was retarded etc. and I suppose catalytic convertors restricted exhaust somewhat.


I'm curious as to the nature of the conversion on your car. Did they change out the distributor and carburetor? If so, what parts were used? I completely removed the computer unit from the air cleaner and stored it away. There are only four sheet metal screws holding it on. It leaves some holes in the air cleaner where is was mounted but that will allow more air to enter...poor man's version of a dual snorkel. Any specs you can provide would be welcome, it sounds like your car is running fine.

 

[306Doba]

I'll get some pictures for you tonight, don't know much about wiring/electronics so I won't really be able to explain the setup very good, sorry. I was told by someone looking at the motor that it had been done though so next time I see him i'll get a better description for you. The computer box is still mounted on the air cleaner.

Thanks alot for the info!

 

[LS-300]

In the process of the conversion the old "computer" must still be hooked up. Unfortunately there are other things that are hooked up using it. Like the AC unit and possibly the cruise control. I forget exactly what all it controls but others have found out the hard way about just removing it.

 

[ArtH]

Hmmm, that doesn't sound very encouraging. I can live without cruise control if need be, I rarely use it on any of my cars but A/C is another matter. It wasn't working when I first got the car, but we feel like that was due to lack of refrigerant. I checked the system and it appears it has all leaked out. Normally, A/C will not switch on if the pressure is low, I think there's a switch to prevent that from happening. The compressor is not locked, but the clutch doesn't engage. My plans were to convert that over to R134a as I have done on other old cars successfully, it's much cheaper than R12 which is very hard to find and expensive when you can get it. We have a couple of pretty good techs in our service department, I'll let them sort the A/C problem out. I bet they can get it working if anyone can. All other systems work fine such has heater and blower motor so if I can get the A/C fixed, I think I'm home free. Bet someone else has already worked around this problem.

 

[306Doba]

As far as I can see there are no wires connected to my computer, unless they're hidden, and my AC and cruise work fine.

Not sure if these pictures are of any use to you, I will get some better ones with the air cleaner off when I have time.

 

[ArtH]

I think your engine was converted to a Mopar electronic system. Today I tested my car on the road and the cruise control worked fine. I know the A/C is out due to lack of refrigerant, I think they were still using R12 in 77. I've had a couple cars converted to R134a with no problems so eventually I will have that done with this car. The only electrical connection I see is some sort of sensor or compensator for the increase load the A/C compressor puts on the engine, it would appear to increase the idle to prevent stalling. I've dealt with that problem on other cars as well.

My car drove well but didn't seem to have the power it should have. I think that has more to do with ignition timing more than anything else. I'll have to adjust that some until it feels right.

 

[Jonnyuma]

You're right, Art. The LeanBurn computer has absolutely nothing to do with the a/c or cruise control. These things are a completely different animal than modern engine management computers. Theyre analog for starters, and were'nt particularly good at "spark control" much less trying to handle any ancilliary functions like climate control. The cruise control is a completely separate system, has nothing to do w the LeanBurn.
Theres an idle increase solenoid (I forget the true name for it) that will kick up the idle rpm when you engage the a/c compressor, but its not connected to the computer. It simply increases the idle speed to compensate for the drag of the a/c compressor. Get yourself a good adjustable vacuum advance distributor, and the intake and carb of your choice. Block off all the egr garbage and run a decent pcv valve...you'll be golden.

 

[ArtH]

Thanks for the help on this. Johnnyuma, I agree with your post all the way. It makes sense. I know the cruise will work without the computer and I don't see where the A/C will be an issue once I get the system checked out. That's an area I very little knowledge or experience and know it's potentially dangerous if you don't know what you are doing. I once started unscrewing a line on an old Chevy truck A/C unit only to have it burst loose and spew freon (I guess that's what it was) under pressure for about 10 or 15 seconds under high pressure. I wouldn't have thought there was anything left in that old system. After that, I did learn to use gauges.

Right now, I'm experimenting with timing. The oem sticker under the hood calls for 20* BTC but obviously this is for the computer. I started with 10 and no vacuum but that was definitely retarded as I ear tuned a bit more advance and the car performed much better. I'm not trying to hot rod this car just make it a decent driving vehicle. Anyway, it's getting there. Again, thanks a heap!

 

[WP29440SE]

change the distributor to a standard EI unit. i found my lean burn distributor was different and had a different vacuum advance pod and the lean burn system controlled my advance

 

[ArtH]

The LB distributor was replaced with a Pertronix distributor with conventional vacuum advance unit. I've used Pertronix modules on other cars and currently have one on my 72 Lincoln. It works fine. I also rigged up the GM HEI system that slantsixdan referred me to. All I need is a electronic distributor to finish that project should the Pertronix distributor fail...I'm told it will, we'll see. I had to play with the initial timing some to get the engine run smoothly. I noticed the engine tune up spec sticker attached to the hood states 20* BTC at 750 RPM however, that's using the LB system.

I still have to get the A/C looked at but that's one job I know very little about and I don't have any of the equipment to do the job anyhow. I haven't driven the car much due to no A/C and 100 * temps. I'm old and spoiled, I like A/C.

One thing I should point out to others if you decide to go with the Pertronix distributor. It is a very tight fit against the cylinder head and I had to grind some metal off the corner of the head in order to get the distributor to seat fully and be able to adjust timing. It took me about 1/2 hour of grind, test fit, remove, grind some more etc. Everything finally dropped into place and I easily adjust timing. I didn't have to remove much material and it didn't effect the integrity of the casting. I don't that would have been necessary had I just gone with the GM HEI system and used a Mopar electronic distributor.

 

[WP29440SE]

yep, Dan is all over the place LOL, i still prefer my mopar EI

 

[ArtH]

Seems like a nice guy, I hope I meet him some day.