engine woes

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Mar 1, 2014 | 07:58 AM

Schickel

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Joined: Jul 2012

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engine woes

So heres the story. I have a 77 f250 4x4 with a 400m and manual transmission built up bored out bigger cam that I use as my pulling truck (the 300 ft kind). Last summer as I would go down the track it would sputter at around 5000 rpm but run great below that. In order to fix the problem I bought an entire msd ignition system (coil, wires, plugs, 6al box, distributor cap) thinking I didn't have enough spark. Well last week I finally finished it and much to my dismay now it idles fine but the second you hit around 2300 rpm it starts running horribly sputtering and dieing. I thought it was something with the vacuum advance so I bought an entire new distributor but that didn't help at all. So now im stuck. I have literally no idea what next. I appreciate you taking the time to read all this and if you have any suggestions or help to offer id gladly take it

Mar 1, 2014 | 08:16 AM

HIO Silver

Fleet Owner

Joined: Dec 2009

Posts: 20,678

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From: NorCal

With a hotter spark and more complete combustion, I think the engine is going lean. Did ya re-tune the carb to compensate? That's where I would start due to the new combination.

Mar 1, 2014 | 08:21 AM

77&79F250

Moderator & parts slinger

Joined: Feb 2007

Posts: 50,188

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From: S/W Missouri, Polk county

Takes 3 things to run right? Air, fuel, spark, sounds like a possible fuel delivery issue, since if sounds like you took care of any possible spark problem.

What carb you using, still have a mechanical fuel pump or electric? And if elec are you running a pressure regulator?