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Lean burn / HEI /Vacuum ??
https://www.slantsix.org/forum/viewtopic.php?t=56098		 Page 1 of 1
Author:  Rick Covalt [ Mon Sep 01, 2014 12:13 pm ]
Post subject:  Lean burn / HEI /Vacuum ??
I have the 86 D100 with 30,000 Miles on it. I installed the HEI ignition/Distributor today and all went well. It fired right up and I set the timing. I left the lean burn carb / intake on temporarily until I install the super six. My problem is, where can I pick up vacuum for the new distributor? It has 5 vacuum ports on the carb and 4 of them have full (20") of vacuum at idle. The other port has no vacuum at all even when I open the throttle. Any help appreciated.

Rick
Author:  Reed [ Mon Sep 01, 2014 12:51 pm ]
Post subject: 
You can't use the distributor vacuum advance with some types of lean burn carb. The lean burn carb was designed with a port that gave full vacuum to the computer at all times. There were some "crossover" years where the carbs had the "ESA" port as well as the standard ported vacuum advance prot, but the later years of lean burn carb only had the "ESA" port.

You will have to either swap to a non-lean burn carb or run the HEI and standard distributor without the vacuum advance.
Author:  Rick Covalt [ Mon Sep 01, 2014 1:35 pm ]
Post subject: 
I went back out to the garage and checked the vacuum signal at the lean burn computer and it did change with throttle movement. I hooked that up and slowed the idle down a bit and it runs just fine. Actually runs really good compared to the lean burn set-up. Even if it is not 100% correct it will run for a week or two until I swap over to the super six. Then it will really run nice!! :lol:

Thanks Reed!

Rick
Author:  Reed [ Mon Sep 01, 2014 2:11 pm ]
Post subject: 
If you have installed an HEI ignition then the lean burn computer won't control the vacuum advance. Hooking the full-time vacuum back up to the computer might affect how the computer controls the fuel mixture, or it might not.

The computer calculates the timing based on full vacuum it idle and decreased vacuum at different throttle positions. You will see a change in the vacuum signal to the computer as the throttle is opened.
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