I just purchased a 68 F150.
I was told that the 390 was out of Mustang (possibly 390 GT)
or Fairlane GT as per a local ford collector.
It has a problem of running rich and fouling plugs ater 2 tanks of fuel.I'm sure I have done a good tune-up with plugs,points,condensor,wires.Rebuilt carb(650 Holley w/vac sec).
it still fouls plugs though.
There isn't any smoke ,it starts easy,and it runs good until the plugs foul.
It has an Ford Alum intake ,headers,C6 w/shift kit,3.70 Traction lock.

Does anyone have any ideas why this is happening?

 

You may want to look towards your ignition system. Mine was the same way for a while. The spark just wasn't good enough when the engine was cold and it would foul the plugs on startup. Get an MSD coil and replace the points with a pertronix unit. When you are posting please do not type in all caps. It is hard to read that way. Welcome to FTE!!!

 

Camshaft timing. Set it straight up. Give us the part number on the intake. Post back.
William in Atlanta

 

What makes you say that William? It is a possibility but the chance seems pretty remote to me.

 

Rat! Couple of things make me ask about the cam. Someone has been in the engine and it is not the correct one for this truck. The “Ford collector” comment sounds like a Dealer blowing smoke! The engine runs fine after tune up and for a considerable distance (two tanks of fuel). Engine idle is smooth and no complaints about miss fire. He has changed the carburetor without any change in engine performance. A camshaft set to far advanced or retarded forces an excessively rich mixture which fouls the plugs. Other things could cause this problem, clogged air cleaner, lack of manifold heat, cold wet climate and more. But Shortrange is comfortable around engines and does his own tune ups. I think he has already checked the obvious and going deep is the next step. I would be interested to see cranking vacuum, running vacuum and cranking compression. Easier would be to peek at the timing chain (bet you a nickel it’s set advanced).
William in Atlanta

 

william, thanks for the reply and you moght have something on the cam timing, i have tried settint the timing with a light (10degree, dist vac unhooked) then with a vac guage, had to move the dist quit a bit to get the eng vac to reach normal vac reading, when driving it pinged a lot , might be a good ideal to check the chain?

 

Make sure the vacuum and mechanical advance are working, too.


1972 F250 Custom Sport Camper Special 4x2 360 2v C6 3.73
Some day hope to shorten to a 104" wheelbase as part of a Broncification project
My FTE Website -- http://www.clubfte.com/users/mlf72f250/index.html
My Galleries -- https://www.ford-trucks.com/user_gallery/displaygallery.php?userid=1108

 

[updated:LAST EDITED ON 14-Dec-02 AT 00:51 AM (EST)]>william, thanks for the reply and you moght have something
>on the cam timing, i have tried settint the timing with a
>light (10degree, dist vac unhooked) then with a vac guage,
>had to move the dist quit a bit to get the eng vac to reach
>normal vac reading, when driving it pinged a lot , might be
>a good ideal to check the chain?

Just a note- The timing you set with a light is ignition timing. Cam timing and Ignition timing are two different things.

Joe