I'll apologize in advance if this has been addressed in posts elsewhere, but I'd like to get a few opinions.

I have a 1958 F100 with a 292 y-block, 2v, 4-speed manual. The other day while driving on the freeway it began bucking violently. I thought it was starving for gas, so I replaced fuel filters, air filter, and even the fuel pump (which had previously been replaced with an electric). None of this seemed to help. I replaced spark plugs and HT leads about 500 miles ago, so I'm assuming they're OK. It seems to start bucking at about 45-50 mph going uphill. Is a carb rebuild the next step, or is there something else that might fix it? New coil maybe? Any suggestions would be appreciated. Thanks.

 

When you replaced the filter, was it clogged?

 

I have seen a damaged clutch/pressure plate cause bucking under load. However, I'd check float level or even rebuild carb before suspecting that.

Might try a fuel flow test. That would let you know if the fuel line is clogged, has a pinhole leak, or the tank's sock is clogged.

 

Might check the point gap too.

 

Sounds like an ignition misfire to me

 

Vacuum leak ??

 

No, the filter was actually pretty clean.

 

I changed out the points when I did the plugs a few months ago. I can check the gap, but I don't think that's moved since then.

 

It's funny you mention the clutch. That's something that's been in the back of my mind, as there's been some slippage under load/acceleration. I've also been noticing the "burnt brake" smell lately. I'm inclined to follow that lead before rebuilding the carb since it obviously needs the clutch regardless. I just wasn't sure if that's something that would have caused bucking rather than loss of power altogether. Why would a worn clutch cause that? Would it be the clutch plate slipping then suddenly grabbing the flywheel?

I'll also check the tank sock. The sending unit is in need of replacement anyway, since I'm getting inaccurate fuel level readings (full tank registering as only a quarter).

 

Fuel usually isn't a cause for bucking, it's usually ignition. Check the wire that goes from the coil to the points. Where it runs under the points plate, they can get chafed and short out intermittently when vacuum advance moves the plate.

 

X2 on what Ross said^^^^^^ . This is your problem I would bet for sure.
Or in that area. I have seen this so many times and it will drive ya nuts.

 

I admit this doesn't happen often but I had a car that was only driven for a one week period each year. When I was done driving each time- I would fill the gas tank to the top. After a few years, it drove just fine from full tank down to half. If I let it get under 1/2 it would buck like a bronco! The tank was pulled and had more than 5 gallons of water in it.

 

Arctic, which one is Ross?

 

Broke dad, I took a look in the tank this morning and it doesn't appear that there's any water in it, unless it's homogenized with the gas really well

 

Ross is ALBUQ F-1