Slant Six Forum :: Lean Burn Carb Question

That looks like non lean burn carb...so next you need to do the EI retrofit to get it to run right... and make sure the correct port on the carb is connected to the vacuum advance pod on the distributor..

I have an old distributor off a lean burn truck and it does not have any vacuum advance mechanism. It's my understanding that the lean burn computer took on the vacuum advance functions by switching between the dual pickups in the distributor.

If you can find one form a late 70s truck or van you will be a bit better off.

The lean burn on the 86 trucks was moved to drivers side fender behind the battery.

Quote:

The lean burn on the 86 trucks was moved to drivers side fender behind the battery.

A y reason for it to be there after swapping over?

Mine has a vacuum advance, the usual two wire connector found on most if not all early distributors and then a second pair of wires with a connector reminiscent of a 4 way flat trailer plug. My air cleaner does not have a big "box" like apparatus on the side of it that says lean burn though.

Open it up and see if there is a mechanical advance system under the pickup plate.

Quote:

Open it up and see if there is a mechanical advance system under the pickup plate.

You want to confirm this...dual pickups typically have not vacuum advance since the first pickup is for start...the second is about 10 degrees phased for run, and the computer does the advance.... If the blank off plate on the ESC distributor was missing a vacuum advance pod can be screwed in place to cover the hole...but the vacuum advance will not work...

1979 Aspen distributor would be fine...if it has a part number tag on the side we can figure out what version it is and how it should be installed...

pull the cap and take a pic as well

If going EI anyway, I'd feel better about using the 1979 version than pulling this one apart to determine what it has and then possibly being let down if it's an ESC distributor with a vacuum advance can stuck in the blank off hole.

Author:	ProCycle [ Sun Dec 27, 2015 8:23 am ]
Post subject:	Re: Yep...
Quote: That looks like non lean burn carb...so next you need to do the EI retrofit to get it to run right... and make sure the correct port on the carb is connected to the vacuum advance pod on the distributor.. I have an old distributor off a lean burn truck and it does not have any vacuum advance mechanism. It's my understanding that the lean burn computer took on the vacuum advance functions by switching between the dual pickups in the distributor. I'm guessing that Chicken Helmet will need to source a different distributor as part of doing the HEI conversion.

Author:	Reed [ Sun Dec 27, 2015 8:39 am ]
Post subject:	Re: Yep...
Quote: I have an old distributor off a lean burn truck and it does not have any vacuum advance mechanism. It's my understanding that the lean burn computer took on the vacuum advance functions by switching between the dual pickups in the distributor. That depends on the lean burn system. When we say "lean burn system," we are actually referring to a family of emissions oriented engine control systems that could be a computer controlled carb only, a computer controlled distributor/timing only, or a combination computer controlled carb and distributor. The "lean burn" systems that had just a computer controlled carb had a normal electronic ignition system with a vacuum advance in the distributor.

Author:	Chicken Helmet [ Sun Dec 27, 2015 10:00 am ]
Post subject:
Mine has a vacuum advance, the usual two wire connector found on most if not all early distributors and then a second pair of wires with a connector reminiscent of a 4 way flat trailer plug. My air cleaner does not have a big "box" like apparatus on the side of it that says lean burn though.

Author:	ProCycle [ Sun Dec 27, 2015 10:35 am ]
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Yeah, I guess it doesn't surprise me that there were many variations of that bad idea

Author:	Chicken Helmet [ Sun Dec 27, 2015 10:36 am ]
Post subject:
Quote: If you can find one form a late 70s truck or van you will be a bit better off. How about a 79 Aspen? I found one from that.

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Lean Burn Carb Question https://slantsix.org/forum/viewtopic.php?t=58867	Page 2 of 6

Author:	Rick Covalt [ Sun Dec 27, 2015 11:25 am ]
Post subject:
The lean burn on the 86 trucks was moved to drivers side fender behind the battery.

Author:	Chicken Helmet [ Sun Dec 27, 2015 12:29 pm ]
Post subject:
Quote: The lean burn on the 86 trucks was moved to drivers side fender behind the battery. A y reason for it to be there after swapping over?

Author:	Reed [ Sun Dec 27, 2015 1:43 pm ]
Post subject:
Quote: Quote: The lean burn on the 86 trucks was moved to drivers side fender behind the battery. A y reason for it to be there after swapping over? Heat + vibration = broken electronics. Mounting the computer on the air cleaner put it in pretty much the hottest part of the engine compartment in a place that vibrate quite a bit. 79 Aspen distributor would be OK. Quote: Mine has a vacuum advance, the usual two wire connector found on most if not all early distributors and then a second pair of wires with a connector reminiscent of a 4 way flat trailer plug. My air cleaner does not have a big "box" like apparatus on the side of it that says lean burn though. Interesting. Your original distributor may be fine. Open it up and see if there is a mechanical advance system under the pickup plate. Some versions of the lean burn system used a separate pickup for staring the engine but still had regular vacuum and mechanical advance.

Author:	DusterIdiot [ Sun Dec 27, 2015 1:53 pm ]
Post subject:	lol....X2
Quote: Open it up and see if there is a mechanical advance system under the pickup plate. You want to confirm this...dual pickups typically have not vacuum advance since the first pickup is for start...the second is about 10 degrees phased for run, and the computer does the advance.... If the blank off plate on the ESC distributor was missing a vacuum advance pod can be screwed in place to cover the hole...but the vacuum advance will not work... 1979 Aspen distributor would be fine...if it has a part number tag on the side we can figure out what version it is and how it should be installed...

Author:	Chicken Helmet [ Sun Dec 27, 2015 1:58 pm ]
Post subject:	Re: lol....X2
Quote: Quote: Open it up and see if there is a mechanical advance system under the pickup plate. You want to confirm this...dual pickups typically have not vacuum advance since the first pickup is for start...the second is about 10 degrees phased for run, and the computer does the advance.... If the blank off plate on the ESC distributor was missing a vacuum advance pod can be screwed in place to cover the hole...but the vacuum advance will not work... 1979 Aspen distributor would be fine...if it has a part number tag on the side we can figure out what version it is and how it should be installed... Not a good picture of the dizzy but if you look close you can see the vacuum chamber and a set of wires coming from either side. I'll get a better pic tomorrow and pull the cap and take a pic as well.

Author:	DusterIdiot [ Sun Dec 27, 2015 3:51 pm ]
Post subject:	This will tell the story...
Quote: pull the cap and take a pic as well Pull the cap and the rotor, and take the picture center and even with the top so we can get a good look at the plate and guts.... It will be interesting.... on the late 2 feed distributors the pick ups are on opposite sides of a fixed plate.... if this arrangement were married to an advance plate when the vacuum advance goes to tug on the plate...the tolerances on the other pickup are going to force the teeth into the reluctor for some not so nice noises and damage to the pickup and reluctor....

Author:	Chicken Helmet [ Mon Dec 28, 2015 7:33 am ]
Post subject:
Distributor with cap off: Extra Plug: Rotor Off:

Author:	DusterIdiot [ Mon Dec 28, 2015 6:03 pm ]
Post subject:	Hmmm....
Still a little hard to tell with the pics as is, but a few things are evident... 1) Your distributor still has an OEM Part number tag on it. 2) It has dual pickups with the correct plugs, but I'm not seeing the tell tale 'dot' you would find near the pickup in the lower part of the picture where the nub on the vacuum advance arm would poke through the top plate on those model distributors... 3) Also hard to see if you have advance weights under the plate (if they weren't caked with grime they'd stick out in the voids in the plate and be easier to spot. If going EI anyway, I'd feel better about using the 1979 version than pulling this one apart to determine what it has and then possibly being let down if it's an ESC distributor with a vacuum advance can stuck in the blank off hole. One true way to tell would be to hook a hand vacuum pump to the vacc. advance pod and see if the pickups move in relation to the center post as you add more vacuum to it.... (i.e. about 5-14" would show it)...if the pod is blown you will pump all day and never get anything out of it...

Author:	Reed [ Mon Dec 28, 2015 6:18 pm ]
Post subject:	Re: Hmmm....
Quote: If going EI anyway, I'd feel better about using the 1979 version than pulling this one apart to determine what it has and then possibly being let down if it's an ESC distributor with a vacuum advance can stuck in the blank off hole. x2

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Author:	Chicken Helmet [ Tue Dec 29, 2015 2:56 am ]
Post subject:
The other distributor is on the way and the ignition stuff should be here today. Thanks again for everyones help.