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Won't Idle Running Lean
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Author:  Rug_Trucker [ Wed Sep 26, 2012 4:47 pm ]
Post subject:  Won't Idle Running Lean
Rebuilt a super six BBD and swapped it onto a friend's van a couple of years ago. It has got to the point of running really lean on idle.

Pulled the NGK's and they were pretty tan. Very even looking. Did a hot lash stock setting valve adjustment.

Someone else futzed with the carb and took the idle mixture screws all the way out, and cranked the idle screw all the way in. He also played with the timing. :roll:

He tells me that idle idles fine either nose down, or nose up on a grade. :shock:

I can't think this would be the float height as it shouldn't have changed. Right? If it was sinking it would be running rich.

I can only get 15" of idle. It runs like a scalded monkey on the road. No pinging.

I don't know what the timing is set at. I ran out of time to work on it.

When I pulled the fuel line to remove the valve cover not a drop of gas.

Also changed the PCV valve, then plugged it (some slight improvement.)

Snugged the carb down.

Sprayed propane around the electroweld POS '77-78 vintage aluminum intake.

Changed EGR's, flipped the EGR.

I told him to plug the hose going to the brake booster. I haven't heard if he did that yet.
Author:  Rug_Trucker [ Thu Sep 27, 2012 2:57 pm ]
Post subject: 
No ideas?
Author:  SlantSixDan [ Thu Sep 27, 2012 3:05 pm ]
Post subject:  Re: Won't Idle Running Lean
No good advice possible because too much "I donno" and "I guess" "I haven't heard" and weird stuff (blocked off PCV valve...) in the question.
Author:  Reed [ Thu Sep 27, 2012 5:33 pm ]
Post subject:  Re: Won't Idle Running Lean
Quote:
Someone else futzed with the carb and took the idle mixture screws all the way out, and cranked the idle screw all the way in
Have these errors been corrected yet?
Quote:
He also played with the timing
Has this been checked and corrected?

Something many people either forget to do, do wrong, or don't know to do is set the metering rods on a BBD. If you can get your hands on this van and carb, do the following:
(.5) Reattach the PCV valve.
(1) Verify that the timing mark on the vibration dampener is in the correct place and indicating true TDC.
(2) Verify that the idle mixture screws are installed properly.
(3) Set the curb idle and mixture and timing properly.
(4) Set the metering rods properly.
(5) Verify that the BBD is not a 318 BBD. In other words, make sure the choke thermostat rod (I think I got the name of the part correct) hasn't been all bent out of shape by someone trying to for the slant six BBD choke thermostat linkage to work on a 318 BBD.
Author:  Rug_Trucker [ Thu Sep 27, 2012 7:04 pm ]
Post subject: 
I only plugged the PCV for a couple of seconds with my finger.

We ran out of time. He lives 45mi from me. I work 14+hr days. The way the carb was adjusted it runs better than it did. Still very lean.

I rebuillt the carb a couple of years ago. It set it up right. It ran great for a couple of years. Perhaps the ethanol has done a number on it. I suggested remving the screws and letting the gas run out. Maybe shoot some cleaner in there. He doesn't need to open the carb! He screwed up the valve adjustment on the original factory head years ago.

He is a much better songwriter! :lol: He had a cut many years ago with Jimmy Buffet.

Reed I don't think the metering rods are going to effect the idle. If they were off it would be rich. It runs with lots of power on the road.

We need to examine the intake.

The carb is a SS BBD thick air horn, right sized orifices in the idle scew area, bent PCV fitting. Correct choke etc. It was a complete swap from his 78 van. I rebuilt the carb when we swapped the "RV prepped head."

I shot propane straight down the carb throat. It idled a little better.
Author:  Reed [ Thu Sep 27, 2012 7:58 pm ]
Post subject: 
How is the throttle shaft condition? Time for a rebush?
Author:  Rug_Trucker [ Fri Sep 28, 2012 3:46 am ]
Post subject: 
Quote:
How is the throttle shaft condition? Time for a rebush?
Tight
Author:  Rug_Trucker [ Sat Nov 03, 2012 3:05 pm ]
Post subject: 
Here is what may be the final chapter.

A week ago we think it back fired through the carb. He richened it on the idle after that. He claimed it was idling better, not great, better. He brought it over today. It was idling rough, and still pulling 15". I adjusted the blades up and turned the mixture screws to 2 1/2 turns. Got 21" and checked the timing. It was at 12*

It is smooth as silk, the exhaust smells clean.

He drove away a happy man. :D

BTW still have the elctro welded amooleenum intake on it.

Monday is run it through MARTA to get the OK for another year.
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