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Unread 08-11-2013, 10:39 PM   #1
stephenspann27
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Need Advice tuning a motorcraft 2100

I picked up a '75 CJ5 last week. I've been trying to get it to run right ever since. The first glaring issues I found was the top gasket on the carb wasn't even close to being in the right position at the back of the carb. The second issue is that the float level was set way too high.
After these two changes, it the jeep is now drivable. The idle mixture screws were nearly 3 turns out, I think i have them somewhere around 2.5 turns right now. It lopes quite a bit at idle as if it has a large cam. Tonight I played with some different positions for the accelerator pump. It started in the 'stock position" which I think is the second hole from the top. It seemed to run better on the upper holes than the lower holes.
There are two problems remaining, coming off idle, when you are letting the clutch out, it falls on it's face a bit, then cleans up until you get past 1/4 throttle and it gets crappy again. If you got WOT, it will just bang out really bad, it won't ever clean up. I pulled two of the plugs that I installed two days ago, they were both nice and white. I'm thinking maybe I'm dealing with a lean issue rather than rich. I think I remember the jets being #47s. The motor has headers.. and possibly a cam. what size jets are you guys running? This is a 304 V8 in a '75 CJ5.

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Unread 08-12-2013, 08:24 AM   #2
stephenspann27
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I took apart the powervalve.. and I'm wondering if the spring loaded brass plug is some sort of adjustment? I didn't note it's position before I took it apart. I understand that to select the proper powervavle you need to drive the vehicle at 1/4 throttle and get a vacuum reading from the base of the carb?
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Unread 08-12-2013, 09:01 AM   #3
jeepwhore
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As far as I know they aren't adjustable. But they come in single and dual stage with several ranges to choose from.
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Unread 08-12-2013, 10:39 AM   #4
stephenspann27
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The little brass plug has a spring under it.. by turning the plug in our out you are changing the spring tension.. I'll see if I can find a good picture of one and get mine in roughly the same position.
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Unread 08-12-2013, 10:59 AM   #5
stephenspann27
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Awesome doc here: looks like I have a dual stage powervavle. http://street2mud.com/webfiles/MC-21...%20a%20258.pdf

"• Do not try to disassemble the PV itself, it's fixed on precise calibration."
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Unread 08-12-2013, 11:23 AM   #6
stephenspann27
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Also, it looks like my vacuum advance is hooked to the wrong port of the carb. Can anyone tell me what size jet's they are running?
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Unread 08-16-2013, 09:46 PM   #7
stephenspann27
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Found the culprit. The distributor hold down was loose. Set the timing, and and tightened it. Runs good now.
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