I just bought a 79 dodge aspen with slant 6. How can I tell if the engine has Lean Burn system?

Your '79 shouldn't have it, but to check, look and see if there's a box attached to the air cleaner housing that says "ELECTRONIC LEAN BURN" or "ELECTRONIC SPARK CONTROL" or somesuch language. If so, then yes. If not, then no.

http://www.slantsix.org/articles/leanbu ... rticle.htm

Look for the standard ECU. if should be mounted to the passenger side fender. If you have the ECU, that means that you do not have to worry about lean burn.

I've been told that lean burn was not used on slant sixes until after 1980. That means that only v-8 aspens ever had lean burn.

Your '79' should have just about the best ignition system chrysler ever made.

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1980 Aspen 225 super six

I noticed in the article that the ported vacuuom switch is to prevent the vac advance from activating during warm up. Is this correct. I thought the device was for the EGR system. Does someone have a diagram of what the hookup should be for my '74 225. I have the distributor vac advance going directly to the carburetor right now.

Thanks

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Sweet Emotion

Ported Vacuum Switches can be used for thermal on/off control of vacuum in any system. In Mopar's '70s-'80s emission control systems, the PVS is generally used to prevent the EGR system from working before the engine is up to operating temperature, and not to prevent the vacuum advance from operating when the engine is cold.

Cold engines inherently produce less NOx than hot engines, and NOx control devices cause large driveability problems on cold engines. So, they are deactivated until they're needed (i.e., until the engine is at operating temperature).

The primary distributor vacuum advance NOx control is the OSAC valve.

Remember, though, that in the '70s and early '80s there were many differences emission control systems depending on the specific engine, transmission, vehicle, production date and intended market. It's tough to go by generalized information presented in "reader's digest" type aftermarket manuals, because it's often not quite correct for the vehicle at hand.

And you should leave the distributor vacuum line connected directly to the carburetor, as you have it now.