Header install
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Header install
So i just got my headers installed. It's on a 351w
Now i don't have any exhaust installed other then the headers, and i wanted to tune the truck some more.
After i kicked off the high idle and the choke was off, the tach was reading 1100 in park. Now i would put it in drive ( and before the header install it would idle in drive at 600) now it just dies as if it's too low of an idle.
At a loss here.
Now i don't have any exhaust installed other then the headers, and i wanted to tune the truck some more.
After i kicked off the high idle and the choke was off, the tach was reading 1100 in park. Now i would put it in drive ( and before the header install it would idle in drive at 600) now it just dies as if it's too low of an idle.
At a loss here.
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From: Dallas, GA
Well you mention high idle and choke so I'm assuming it has a carb.
Almost sounds like it's getting hung up on the high idle still. did you bother the choke at all? How about the electrical feed to it? That comes up on the passenger side by the headers right?
Almost sounds like it's getting hung up on the high idle still. did you bother the choke at all? How about the electrical feed to it? That comes up on the passenger side by the headers right?
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It's not injected, it has a 4180 carb on it. I had just fixed the choke and fast idle cam before doing this install.
I checked to see if fast idle cam kicked off and it did, and choke opened all the way.
It was idling at 1500 at this point in park, so i unscrewed the idle screw abit to get down to 1100.
Then when i put it into gear it sputters and dies. This of course is all after i let the engine warm up
I checked to see if fast idle cam kicked off and it did, and choke opened all the way.
It was idling at 1500 at this point in park, so i unscrewed the idle screw abit to get down to 1100.
Then when i put it into gear it sputters and dies. This of course is all after i let the engine warm up
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It should be idling more like 750 in neutral or Park and drop to 600+ in gear. Dropping it in gear at 1100 RPM is rough on things.
It sounds like your idle mix is way off. I don't know why it would be with just installing headers, so I'm thinking it is something else, like vacuum lines, plural, off. Or the carb isn't bolted down. Work to get your idle down to ~750 and very smooth, using a vacuum gauge to tune the idle mix. You should have something like 19 or 20" of vacuum at that RPM. I'll bet when you get it to idle at that speed with that vacuum it'll drop in gear and settle down to ~600.
It sounds like your idle mix is way off. I don't know why it would be with just installing headers, so I'm thinking it is something else, like vacuum lines, plural, off. Or the carb isn't bolted down. Work to get your idle down to ~750 and very smooth, using a vacuum gauge to tune the idle mix. You should have something like 19 or 20" of vacuum at that RPM. I'll bet when you get it to idle at that speed with that vacuum it'll drop in gear and settle down to ~600.
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From: Dallas, GA
I'm far from a carb expert but was told by a friend once that when he put headers on his Mustang it reduced the back pressure so much that he ended up having to change the power valve....It apparently also changed manifold vacuum.
I'm not sure how accurate or possible this would be...but if it is, then it would also be reasonable that it would change the idle mixture.
Sounds like a good question for Bill
I'm not sure how accurate or possible this would be...but if it is, then it would also be reasonable that it would change the idle mixture.
Sounds like a good question for Bill
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Also, when removing the drivers side exhauset manifold, i removed this as well (item in picture) it was hooked up to a vacuum tree on the back of the intake manifold, when i removed it i capped of the vacuum line on the intake.
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That's the vacuum-operated heat riser. When shut it forces exhaust through the passage in the bottom of the intake manifold to the other side of the engine. That raises the temp of the incoming air/fuel mix and helps the engine run in cold weather. Vacuum then was applied to it when the engine got warm to allow exhaust to come out on the driver's side.
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Ok so I fixed my problem. I retarded my timing slightly to get the idle smoother.
Then I turned the idle mixture screws back one turn each ( this gave me the highest rpm, and smoothest idle)
Then I set my curb idle.
Truck starts and runs like a top now
Then I turned the idle mixture screws back one turn each ( this gave me the highest rpm, and smoothest idle)
Then I set my curb idle.
Truck starts and runs like a top now
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masseysbronco
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Oct 4, 2010 06:45 PM
