Testing whether cylinders are running

The fan belt is the biggest safety issue. The plug wires are insulated so you should be okay there. Heat would be another factor so you'd need insulated gloves.

Maybe you could disconnect them at the distributor.  There could be some sparing there.

Disconnecting them at the distributor end is safer. No heat. The wire has no spark going thru it  if. it's disconnected  from the distributor and the spark will seek grounding to the wire when it comes in close proximity again rather than your hand.  Suggestion....loosen all the wires at the cap first before doing the test. Sometimes they can be real hard to pull out.........Bruce

I check it by touching the headers. But then that’s easy on my Spyder and my Ducati.

If you've got an old inductive timing light you can just put that on each lead and see if it's firing. Easy-peasy.

Marshall, I suspect you just can't leave it alone and enjoy it.

You have single throat carbs. They ALWAYS sound like it's not running on all 4 sometimes.

We start with an IR thermometer and hit each header pipe.  If its truly a dead cylinder that tells the tale instantly.  From there, plug wires is a good method

I don’t have an IR thermometer…yet.

For now I use a spray bottle with good old H2O and squirt each header tube near the cylinder head and away from the other tubes.

If the water doesn’t vaporize, the cylinder isn’t firing.  From there I work my way back.

@chines1 posted:

We start with an IR thermometer and hit each header pipe.  If its truly a dead cylinder that tells the tale instantly.  From there, plug wires is a good method

I have those built into my fingers. Pretty cool.

@dlearl476 posted:

I have those built into my fingers. Pretty HOT.

I fixed it for ya.

@JMM (Michael) posted:

I fixed it for ya.

He used to have finger Tips .  

@IaM-Ray posted:

He used to have finger Tips .  

Nah. I learned how to tell if something was hot with my fingers without getting burnt back when I was a kid.

Now, if I could just figure out how to check my oil when my car is hot I’d have it made.

burnt fingertips..its only a 4 cylinder..have 6 fingers left...pity the Italian guys with the 12 cylinders

@IaM-Ray posted:

He used to have finger Tips .  

All of us in the witless protection program get a plastic clown car to help us remain anonymous.

An update.  I have pulled the plugs at various times.  Everything seems fine.

I do notice a sound (pitch?) change and a slight loss of power sometimes during a long or hard drive.  Have pulled over and pulled plugs to check.  Seems OK.

I am beginning to wonder whether I should change the plug wires.  I've basically had to change everything else provided with this car.  Why stop now?

I realize that I could have a coil issue but I'll address that separately.

Thanks to everyone who has provided advice on this.

Marshall

What distributor are you running? Have you checked/lubed it lately?

SVDA dizzies are notorious for poor running (which is why most people binned them in favor of mechanical advance 009’s BITD)  Mechanical advance dists also have issues if the springs are weak or if they’re improperly lubbed and sticky.

If you have an electronic ignition, they have their own set of issues.

But a new set of points, rotor, cap, wires and plugs is a good place to start. Even if you have an LX ignition, the spark is still transmitted via cap, rotor, and wires.

As for coil, it’s easy to check, AFAIK, there’s no such thing as a “weak” coil. It’s either in spec or it’s not.

From Aircooled.net:

“Another test for the Bosch Blue coil, is to use an Ohmmeter and with all the wires taken off the terminals of the coil attach the positive and negative, red and black, wires of the meter to first the terminal 1 and 15 that are printed (stamped) on the coil. You should have a reading of at least 3-4.5 ohms, which is the resistance reading inside the coil. A bad coil will show a higher reading then 3-4.5, you want less resistance. Next, place the red or black lead from the meter to the center of the coil (secondary post), and to either one of the terminals, again 1 or 15 on the coil. You want 9500-10000Ohms, sometimes you'll see less, but you don't want to see something like 11,000. Or if you have no reading in either case, the coil is trash.”