timing issue
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New User
Joined: Sep 2006
Posts: 17
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From: Atlanta area
timing issue
75 f-100 390 2bbl from factory got a re-built 400 now. I'm a total rookie mechanic but I want to try to adjust the timing slightly and see if I can get a better idol.
what do you loosen so the distributer can be turned?
Thanks for the help.
B
what do you loosen so the distributer can be turned?
Thanks for the help.
B
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
There is a hold-down clamp with a bolt under the distributor. On many 400's, it takes a special distributor wrench, but depending on how cluttered your accessory drive is, you may be able to get away with a crow's foot or just a box-end.
Just as a side note, this really isn't the way to go about your issue. Timing is something you should set to specification. Turning the distributor blindly is going to cause problems for you. A timing light with white paint is the proper way to time an engine. If you have idle problems with the timing set to spec, you have other issues, such as a possible vacuum leak or poorly-tuned carburetor. If you need to check your timing, we can go over the procedure for this, but I don't recommend doing what you're set out to do as it stands. If you're having problems with your idle, describe them and we'd all be happy to lend a hand!
Just as a side note, this really isn't the way to go about your issue. Timing is something you should set to specification. Turning the distributor blindly is going to cause problems for you. A timing light with white paint is the proper way to time an engine. If you have idle problems with the timing set to spec, you have other issues, such as a possible vacuum leak or poorly-tuned carburetor. If you need to check your timing, we can go over the procedure for this, but I don't recommend doing what you're set out to do as it stands. If you're having problems with your idle, describe them and we'd all be happy to lend a hand!
Elder User
Joined: Mar 2007
Posts: 592
Likes: 1
From: Tooele, UT
Welcome to FTE. There is a little bolt at the base of the dist on top of the hold down. Should be a half inch size just lossen it up then turn the dist where you want it. When you get it where you would like it then just tighten it down again.
More Turbo
Joined: Jan 2001
Posts: 574
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From: New England
IIRC counterclockwise will advance it, raising rpms, leaning out the engine, so you will have to lower idle with the screw. It willbe hard to start if it is advanced too much.
clockwise will retard the timing, and will have opposite affects as above.
am i right on the direction to advance/retard anyone?
clockwise will retard the timing, and will have opposite affects as above.
am i right on the direction to advance/retard anyone?
Elder User
Joined: Mar 2007
Posts: 592
Likes: 1
From: Tooele, UT
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New User
Joined: Sep 2006
Posts: 17
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From: Atlanta area
Thanks for the feedback guys!!! Y'all have convinced me to leave the timing alone. This truck runs GREAT once I get it on the road. The timing must be good..right? I now believe i have a carb issue...fuel/air maybe.???
i had a shop put a re-built carb on it about a year ago. I don't drive this truck much at all. The carb is clean as a whistle. I had a nagging problem of the carb overflowing so I bent the float tang til it quit. Now I have the idle problem. I suppose it is time to go to a carb guy and let a pro do it. Working on these carbs is more like an art than a science. Other than bending the float back a little and risking the overflow problem returning...I'm out of ideas.
Thoughts??
B
i had a shop put a re-built carb on it about a year ago. I don't drive this truck much at all. The carb is clean as a whistle. I had a nagging problem of the carb overflowing so I bent the float tang til it quit. Now I have the idle problem. I suppose it is time to go to a carb guy and let a pro do it. Working on these carbs is more like an art than a science. Other than bending the float back a little and risking the overflow problem returning...I'm out of ideas.
Thoughts??
B
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MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Setting the float is not a trial-and-error procedure, it must be set exactly to factory specification because even being 1/16" off can make you flood out. Unfortunately there are no sight plugs or similar conveniences on a stock 2-barrel carburetor. There are two ways to do it on a stock carburetor - a wet-check procedure which is tricky especially if you don't have experience working on carbs, and a dry-check which is done with the carburetor off the engine during the carb rebuild.
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New User
Joined: Sep 2006
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From: Atlanta area
Great feedback. Since i have decided not to mess with the timing, how about some help with this idle problem.
The truck runs great on the road. She cranks easily...but I have to feather the gas peddle to keep her running. When I put her in drive or reverse I have to give it gas to keep it cranked. I even have to slip into neutral when coming to a stop and work the gas to keep running.
Again...She runs strong on the road...just can't get a decent idle. BTW...had a re-built carb put on @ a year ago and idled fine for awhile. Then I started getting overflow from the carb. I replaced needle and seat...still overflowed. I bent the float just enough to stop the overflow and that's when the idle problem showed up. I do have the wet check gauge and have it as close as I can get it to spec. When I had it dead on spec...the overflow problem comes back. Too bad they didnt have EFI in 1975.
Thanks
B
The truck runs great on the road. She cranks easily...but I have to feather the gas peddle to keep her running. When I put her in drive or reverse I have to give it gas to keep it cranked. I even have to slip into neutral when coming to a stop and work the gas to keep running.
Again...She runs strong on the road...just can't get a decent idle. BTW...had a re-built carb put on @ a year ago and idled fine for awhile. Then I started getting overflow from the carb. I replaced needle and seat...still overflowed. I bent the float just enough to stop the overflow and that's when the idle problem showed up. I do have the wet check gauge and have it as close as I can get it to spec. When I had it dead on spec...the overflow problem comes back. Too bad they didnt have EFI in 1975.
Thanks
B
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
What do you mean by wet check gauge? All you do a wet check with is a small ruler. Is that what you meant?
Can you describe what you did to check the wet float height? If you set it to spec, it should not flood out. If it does flood out, something is installed incorrectly, or you are not measuring the height properly, which is why I have asked you to tell me how you did it. We can troubleshoot from there.
Can you describe what you did to check the wet float height? If you set it to spec, it should not flood out. If it does flood out, something is installed incorrectly, or you are not measuring the height properly, which is why I have asked you to tell me how you did it. We can troubleshoot from there.
