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mc2100 help needed

2K views 14 replies 4 participants last post by  atblis 
#1 ·
just completed the mc2100 1.14 swap on a 1980 cj7 w/ 258 that has all the emissions removed. I also done the tfi igntion upgrade. Heres the problem the engine idles fine but as soon as you throttle up it spits and sputters then clears up and runs fine. The other problem is that it is running rich, as it idles it puffs black smoke, and is fouling the plugs. How do i fix this. Here is what ive tried, rejetted to 45's, changed gasket, checked and set timming to 8 btdc, sprayed crab cleaner at base of carb to ensure there is no leak. I have noticed that this carb does not respond to change, i have screwed the mixture screws all the way in then backed them out 2 1/2 turns then back in 1/8 turn and hardly no response. Ive checked the float depth and set it at 0.85 in. The only thing i have not changed is the power valve, but i dont think this will help lean out the carb. Ive played with the acc. pump linkage but doesnt help the hesitation. Can anyone help with this problem?
 
#15 · (Edited by Moderator)
Pv

Not at idle. PV only comes in when your vacuum drops below a certain level. The idea is that while driving under load, at some point your vacuum level will be too low to pull fuel from the jets, so in order to enrich the mixture there's the power valve which opens when vacuum drops below a certain point. IIRC The number on the PV indicates the vacuum at which it supposedly opens.

A higher number indicates a PV that opens at a higher vacuum level which would be sooner. If you're jeep leans out while acceleration, especially under load, then you might need a power valve with a higher number. This could help with any "flat spots".

45s might actually be a little lean. I would guess with the way fuel is going, you might want to try going up a couple jets. 47 perhaps. This could help with the sputtering.

Running rich at idle is usually due to
1) Bowl over flowing >> float height, needle valve issue, fuel pressure high
2) Blown power valve>> not being held shut by the engine vacuum

If your plugs are fouled, I do not know if they will unfoul themselves assuming you get everything running right.
 
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