Stumble or slipping at uphill cruising speed...

61 fhead with solex carburetor, msd ignition. Condensor, points, wires, plugs, coil all less that a year old. Has been running great, and over the last month, a gradual slip or hesitation has started when in second or mostly third gear, whem climbing uphill on the road at around 32 in second, and 42 in third. I adjusted the timing and mixture on carb and it purrs. Even when the stumble occurs, it's real quick and more a loss of power for just a second. It does seem to be getting worse however.

Could it be my clutch going out and starting to slip while in gear?

I haven't pulled the fuel pump(less than 2 years old) or fuel lines, but did at fuel additive...

The engine is definitely running on all four cylinders and as no hesitation or symptoms while not moving or running of flat surfaces.

 

still running points........ i would check them anyway. how about power to coil, bad connection somewhere? it sounds like something electrical breaking down under load to me

 

points are still running with msd, but really just function as a switch kind of, dwell doesn't matter, just that they are set to be open enough to spark across. Power to coil is good, the other day I didn't realize that the key was in and pulled wire from coil to dist. and it was sparking an inch or two down to ground.

 

over my head now, i know little to nothing about msd, sounds like you got one hot coil though

 

yeah, spark isn't the problem I don't think, unless it is at the plug...although I have tested each plug to see if they are each firing...

 

plugwire breaking down under load?

 

may fire just fine under no compression, i have seen that, look at the plugs and see if they are all burning the same, if you have a oddball you know at least where to look. or what cylinder is giving a problem, checked the valve adjustment latley? they will expand with heat, and you say it does it on a grade/under load. grade/under load = more heat, more expansion

 

what is strange is that it didn't happen for 6-8 months, and is now getting worse. I know that the wires are 6.5mm instead of 8+ recommended for the ignition. I haven't replaced the plugs lately, and think that that is prob. the first step. I am also thinking about checking fuel line and flushing carb too.

 

sounds like the first stages of a missfire to me, could be valves need adjusted, a plug or wire breakind down etc. if it were me i would pull the plugs and note where they came from (what cylinder) and inspect them to see how they are burning etc, check the gap. if one looks different that is where i would start looking for problems. you could have anything from a simple plug wire going bad to a burned valve. the valves need adjusted on these engines, it was routine maintance back in the day, although i do not know how often it was recomended. and if it is a valve clearance issue it will most defenitly get worse with time, and could result in a valve job. not a pretty site especially on a f head or any other engine that has valves in the block as the motor has to come out,or find sombody with the means to do the work in the vehicle. i would check the clearances just for safe measure

 

by the way, if you suspect a plug wire, after checking the plugs etc, you can swap that wire out with another on the cap, if the problem plug changes its location to the cylinder you moved the wire to then you know its the wire (you have to swap out both the dist end and the plug end of the wire) god i miss the old (SUN) scope like a ekg for a engine if you knew how to read it

 

i'm not familiar at all with the valve clearance...how do you adjust the valves? I had a service manual but my dog ate it(no really)

 

http://www.earlycj5.com/forums/showthread.php?t=57294&highlight=valve+adjustment