Unique Bronco needs help
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Senior User
Joined: Jan 2010
Posts: 259
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From: Great Falls Mt
Unique Bronco needs help
I have an 82 with a 4 spd, originaly had a straight 6. Now has a 351w out of a 92 f-150 BUT it was converted to a 4bbl carb. Has the motorcraft 4180 made by holley, from what ive read its off of early 80s mustangs with the 302HO. It does NOT have air idle mixture screws! The truck runs outstanding wide open and idles well too. but between 1000 and 2500 rpm, it stuters and jerks and doesnt do well at all. It occasionaly dies completely while going down the highway. Im putting a new coil in it tonight, its all I can think of. I rebuilt the carb, set the timing, It wont run at less than 20* tho which I find strange as well. Any less and it runs even worse. Any one have any ideas?
Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
is there a place where idle air screws had been?? you might try a different carb. also when your setting the timing are you plugging the vacum advance? what spark plugs are you using? replaced the fuel filter?
Thread Starter
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Senior User
Joined: Jan 2010
Posts: 259
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From: Great Falls Mt
No place where the screws should be, its a blank plate. Ive read that ford did it on purpose to keep people from tuning their stangs in the early 80s. Supposedly its pre-set perfect from holley. You think the plugs would let it idle good and run wide open but not at a certain RPM range? Ill try it. Thanks.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
It has them... they are behind the blank spot on the casting where it would seem they should be. If you look down through the bores you can see the needle tips of the screws or at the very least feel them with a fingertip. Ford and GM both toyed with this idea taking the possibility to adjust fuel mixture completely out of the question by casting the throttle plate, putting the screws in and setting the mixture, then running more pot metal over the top to "seal" them in. Its tricky but you can expose them to make adjustments if it becomes necessary. Had to do this when a friend swapped engine sizes in an old Country Squire wagon but we re-used the carb.
Personally, I would exhaust any and all OTHER suggestions that you receive here before resorting to chipping out the casting caps.
Personally, I would exhaust any and all OTHER suggestions that you receive here before resorting to chipping out the casting caps.
