1985 f150 5.8 H.O carburetor rebuild - Page 6 - Ford Truck Enthusiasts Forums

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1985 f150 5.8 H.O carburetor rebuild

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  #76  
Old 06-18-2018, 05:43 PM
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Originally Posted by dziwei View Post
I adjusted the primary float bowl needle and seat so no steady drip from sight plug, would this effect idle at all? seems to be running a little rougher, no too bad but different and sounds like it might stumble... maybe just dial it back an 1/8th of a turn to test? been enjoying the test drives in this truck even with the tired shocks (had new tires put on this weekend).
Are you afraid to be messing around the engine while it's running? Don't worry, I was too when I started out a long time ago. But if you can get up the courage, and try not to get caught in the fan, I would turn them with the engine idling and warm like I described.
 
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Old 06-18-2018, 11:46 PM
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Tried it when running but didn't get the feedback I was expecting from moving the needle & seat, felt like I was at a limit adjusting further in and I backed it out a full turn and more but couldn't hear any difference so I just put it where I had been running it and backed off just under a quarter turn, drove it and it idled maybe a tad smoother (like up a few rpms at the stoplights) will see in the morning if cold idle works any better. didn't get to the choke today... Also drove it 55-60mph on the freeway tonite, felt really smooth but air leaks around the windows prevented us from hearing the engine.
 
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Old 06-19-2018, 12:01 PM
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I'm sure this was mentioned already (eight (8) pages on my smart phone...) make sure the ignition timing is straight before trying to adjust the idle mixture too seriously. Crisp feedback response here is dependent on a strong manifold vacuum signal present at the idle circuit, because, very little air moves through carburetor at idle. Retarded or late ignition timing will lower the average manifold vacuum below what the carburetor expects. An oversized carburetor especially won't idle quite as well.
 
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Old 06-19-2018, 07:00 PM
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Originally Posted by Tedster9 View Post
I'm sure this was mentioned already (eight (8) pages on my smart phone...) make sure the ignition timing is straight before trying to adjust the idle mixture too seriously. Crisp feedback response here is dependent on a strong manifold vacuum signal present at the idle circuit, because, very little air moves through carburetor at idle. Retarded or late ignition timing will lower the average manifold vacuum below what the carburetor expects. An oversized carburetor especially won't idle quite as well.
Yes, if the timing is retarded, you will have to open the carb up too much to get it to idle, and if the carb is open too much, your idle screws won't do anything. That is also why I said make sure it's idling down where it should be, not up around 800-1000 rpm. It should be down around 500-600 rpm at idle.

Also this a smog carb, the threads on those idle mixture screws are very fine thread. So it takes a lot of turns to get anything out of it.
 
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Old 06-19-2018, 09:56 PM
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Ah, now they tell me! (just kidding) so as I am googling 'timing adjustments 5.8l Ford v8' do I need special equipment to check timing?

I have driven it 30-40 miles and the idle at stop lights is steady and not revving at all, once in a while when I pulled in to park it seems a little higher, that is when it was good and warm. This morning was typical temperature and humidity (55 degrees and low) and it idled after I gave it extra gas for a second after the engine started, for example: pumped it once, depressed the pedal halfway, turned the key, it started up and I instinctively floored it to make sure it wouldn't die and when let the pedal up it kept running. I really need to make sure the choke is set correct then get after the timing, another day went by and I treated rust in the B-pillars not thinking about under the hood... I should have a number for mileage after my next fillup, that will be interesting.
 
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