Here we go again SIGH.............. It is that time of year again where I have to start hauling hay and my old truck isn't too happy about it. The truck is a 1974 F-350 with a 360 engine. The problem is that the truck is missing throughout the rpm range. It idles excellent and does fine untill you load the motor. once you start accelerating the engine has a sputtering miss to it. it is not a bad miss where you can feel it surge but just a constant stuttering so to speak. It happens from the time you start accelerating in 2nd gear all the way through having it wound out it 4th. No better or worst at any time. Needless to say this does not work too well for hauling, there is absolutely no power. I am leaning towards an ignition/electrical problem because the truck has excellent responce with the carb(stock 2-V-2100)

Where could i start looking at? I have tried setting timing between 8-12* and have reset the point gap to .017. checked the dizzy shafy and it has little play in it. mechanical adv. is set at 10L. Vac advance is and always has been unplugged. sprayed around all gaskets with carb cleaner and didn't find any vac leaks. Spark plugs look ok. so what else??

I am just about tired of fooling with it.
Thanks

 

Poor coil? Bad wires? Coil wire has bad connection? Vacuum leak? Bad gas?

 

I agree, it's an ignition problem. Try a new condensor, plug wires can causes this and even if your plugs look ok, they can cause this also. Could be a weak coil, what color is the spark at the coil and again at the plug end of the wires. Then there is always the old bad dist. cap, either carbon tracked or cracked or dirty.

 

If it was mine, I wouldn't bother troubleshooting. We know it's in the ignition. So... replace plugs, plug wires, points, condensor, cap, and rotor. Before you install the points, slide a piece of paper through them, closed, to clean them. If that doesn't do it, then start messing with the coil.

Just for kicks, try plugging in the vacuum advance after you get this miss fixed. You just might be surprised.

 

yes why is the vacuum advance not plugged in. set base timing to about 12 btdc or 6 if it is all stock sounds like the timing is way to retarded the marks on the balancer could have slipped do you have a vacuum gauge if so use that along with a timing light to set it or set the base timing out more like 15 or 16 and see if it gets better or worse if it gets better you know the marks are not accurate

 

cool. I have replaced just bout all of these parts before. But as you all know new doesn't equal good. I have suspected the ignition of being weak anyhow. I will put another new coil and condensor and points on to start with.

As for the vac. advance- I have never gotten it to run even close to good with it hooked up. since I last tried it though the diaphram has busted so it won't work at all now.

I don't see how the timing marks could move, they are stamped on the harmonic balancer and that is keyed and bolted to the crank. The other mark is bolted to the timing cover. I do not have a vac. gauge though

Thanks for the ideas though

 

well the harmonic balancer is a 2 piece unit look at it a outer and a inner ring and inbetween a rubber belt it is common for the rubber belt to dry out and the outer ring slides

 

Yep I agree with the guys..It sounds like to me the Ignition is breaking down under load....and blowing out the week spark in 1 or more cylinder's.....

Sounds Like a weak coil....If a plug wire would be bad..it would miss all the time...

Just my thoughts..

Good Luck!!

Russ

 

I have a similiar problem with my newly rebuilt 352FE, but its not near as bad as yours. Pop the cap and rotor off and try to move the dizzy shaft back and forth, if you can its worn out. When the dizzy wears out the shaft moves all over the place and causes the timing and Dwell to go all over the place, now you can get a new dizzy from Napa for about $45, or you can do what I did and buy the Crane XR-1, which is an electronic ignition upgrade and put it in, the electonic points elimatnors dont care if the shaft wobbles and it solves the problem. But, the best thing to do is proably just get the remaned dizzy.

I will let you know how the XR-1 works once it arrives from Summit racing.

 

Another thought, I put new plug wires on my 390 in the fall and yesterday I was fiddling around on the motor and found the coil wire AND #1 wire were both cracked!
Definitely explains the miss I had now.........

 

Not necessarily true. Just like a weak coil, a bad plug wire can work ok up to a certain point then either arc or get hot and open up. Seen both happen.

 

Bear is right. I've had plug wires go bad in my '92 Explorer, and it felt like you were going over bumps that weren't there. Got worse with load. I think it's just more noticable under load.

 

Just an amatuer thought. Have you checked the timing at full advance, say around 3000rpm?

 

On the Crane XR-1, I thought that it got it's pickup off the same shaft that opens and closes the points. If so, wouldn't it also have problems if the shaft is loose? Just wondering because if I ever get my 390 back together I was considering the Crane XR-1 myself.

 

Well Ya Might get Lucky and when the sun goes down..and its good and dark..Fire the motor up and look for the Light show..any sparking or arcing..Might Show the Culprit??


Russ