Tuning a 400
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From: S. Mississippi
Tuning a 400
I've got a 79 F-150 with a 400 under the hood, backed by a c6. it is all stock, but when cold has no power what so ever. once it warms up it has passing gear, but no torque. i can't even get it to break the tires loose. it runs fine, pulls fine once its moving. also if you floor it, taking off, either reverse or foreward it doesn't bog, but vibrates really hard, and spins a bit. what could cause this? Any help is appreciated. (i'm not so good with these motorcraft 2bbls)
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Joined: Nov 2001
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Tuning a 400
>I've got a 79 F-150 with a 400 under the hood, backed by a
>c6. it is all stock
I have the same truck and I used to have about the same problem with my stock motor. My timing was too far retarded and it would vibrate really bad until it got into the passing gear RPM range. It would have no low end power but normal top end. When I set the initial timing at 13 degrees, it ran like a champ and could break one tire loose for about a block.
I gained the low end power back and retained the top end power I had before I adjusted the timing.
And about the lack of power when its cold; if the intake doesn't get enough heat to it, the fuel runs down the walls of the intake so that it doesn't mix with the air until it gets to combustion chamber causing poor combustion and lack of power. To correct this you could try to heat the air coming into the carb by attaching the metal tube that goes from your passenger side exhaust manifold to your stock air cleaner if you haven't done so already.
Hope this helps.
Tim
79 F150 4x4 410m Built Ford Tough!(9.1:1,KB pistons,custom Comp Cams X-Treme 210/218-.508/.524,roller rockers)/c6/3.5:1 gears,4.11:1 soon, Demon 4bbl, 285/75R16 BFG Mudders on alumn. mags with New Drk. Blue paint.
65 Ranchero 170-6, 3on the tree, solid mags, New Bright Yellow paint
>c6. it is all stock
I have the same truck and I used to have about the same problem with my stock motor. My timing was too far retarded and it would vibrate really bad until it got into the passing gear RPM range. It would have no low end power but normal top end. When I set the initial timing at 13 degrees, it ran like a champ and could break one tire loose for about a block.
I gained the low end power back and retained the top end power I had before I adjusted the timing.And about the lack of power when its cold; if the intake doesn't get enough heat to it, the fuel runs down the walls of the intake so that it doesn't mix with the air until it gets to combustion chamber causing poor combustion and lack of power. To correct this you could try to heat the air coming into the carb by attaching the metal tube that goes from your passenger side exhaust manifold to your stock air cleaner if you haven't done so already.
Hope this helps.
Tim
79 F150 4x4 410m Built Ford Tough!(9.1:1,KB pistons,custom Comp Cams X-Treme 210/218-.508/.524,roller rockers)/c6/3.5:1 gears,4.11:1 soon, Demon 4bbl, 285/75R16 BFG Mudders on alumn. mags with New Drk. Blue paint.
65 Ranchero 170-6, 3on the tree, solid mags, New Bright Yellow paint
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Posting Guru
Joined: Jan 2001
Posts: 2,357
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From: S. Mississippi
Tuning a 400
well the heat tube is missing from the manifold up to the air cleaner. its been missing since i got it. Im going to find a timing light and try to adjust the timing.about the vibrations. if i let off the gas while cruising at about 60 mph the vibes stop, i get back on it and it goes back to vibrating. The universals sound a little loose when you go from park to reverse or from reverse to drive, i've got the usual clunk. But that doesn't explain my lack of power. if i just barely give it gas it will accelerate fine. if i stomp it it just hesitates and then finally accellerates like mad. any ideas?
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