1964 Some cylinders not firing

[vbudwick]

390fe mostly original except new MSD dist and coil conversion. Car was running fine for a while now. Then one day runs super rough like a big cam. Checked spark plugs to find that 2 cylinders, number 7 & 3 are not firing at all. Plugs wet with gas. 5 and 1 look like new, almost too lean. Rest look to be fine, to some degree. But 7 & 3 not firing at all. Checked firing order, good. Checked compression 120 all around, pretty good. Checked to see if plug had spark, yes and pretty good too. New wires. Swapped around plugs, lean for flooded and no difference just fouled 7 again. So spark yes, fuel yes, compression yes yet can’t get it to run right again. Need some suggestions / ideas. Car ran fine for some time

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[4VE]

390fe mostly original except new MSD dist and coil conversion. Car was running fine for a while now. Then one day runs super rough like a big cam. Checked spark plugs to find that 2 cylinders, number 7 & 3 are not firing at all. Plugs wet with gas. 5 and 1 look like new, almost too lean. Rest look to be fine, to some degree. But 7 & 3 not firing at all. Checked firing order, good. Checked compression 120 all around, pretty good. Checked to see if plug had spark, yes and pretty good too. New wires. Swapped around plugs, lean for flooded and no difference just fouled 7 again. So spark yes, fuel yes, compression yes yet can’t get it to run right again. Need some suggestions / ideas. Car ran fine for some time

Not sure what the MSD distributor is but I suspect it is an electronic ignition system instead of the original mechanical one. I am going to take a shot in the dark on this but I am guessing that the unit is set up for multiple different engine configurations from 4 to maybe 16 cylinder engines. Somehow, it thinks it is firing for a 6 cyl with possibly a different firing order and with a different stroke distance so the frequency is skewed too.

 

[vbudwick]

Car did run fine though. Just drove it to work, 30 miles. And yes electronic ignition

 

[Ward 57]

Car did run fine though. Just drove it to work, 30 miles. And yes electronic ignition

That's why I hate electronics. They can go haywire for no reason at all. Low voltage makes them go berserk. I would recommend getting the make and model number and search the manufacturer's web site for an owners manual and possibly find out how to re-boot or at least see the configurations.

 

[Angry Bird]

I've had Pertronix in my car for more than 20 years and never had a single moment's problem. I would check the distributor cap for cracks so to make sure that there is no moisture build up. There are so many different things that could cause that problem including the voltage regulator. Keep digging!

 

[Frankie the Fink]

Checking the distributor cap for arcing marks, burnt contacts, cracks, etc... is a very good start...
Also checking the engine bay in the dark (in a garage perhaps, with GOOD ventilation) can
sometimes reveal arcing at the plug wires or across distributor towers, etc.. I doubt its a coil
if the same cylinders consistently foul. Been a while since I was around a BB Ford but pulling
spark plug wires off, one at a time, with the engine idling should reveal aboutt a 75-100 RPM drop.
The cylinder(s) that do NOT have this drop are not firing... I know you said you checked it but it never hurts to
double check the firing order; I know it sounds stupid but there is no downside to confirming its correct.

I've run Pertronix for decades, since they were first offered and have installed them in a couple dozen cars with no issues.
The later versions Ignitor III have a myriad of built in protections from failure...

Don't know much about the MSD setups so no help there....the key thing to remember is:
"If you bring air, fuel and spark together, under pressure, at the right time, you'll have combustion"

One of those things is missing...

 

[55blacktie]

In my opinion, MSD components are overrated. My brother's I/O with 408 stroker Ford Windsor had MSD components. Whenever he took his boat out, he spent as much/more time working on the ignition system and making parts runs as he did on the lake. My brother was a professional mechanic, specializing in electronics.

 

[74 Harley]

Another thing to look at is your vacuum hoses. A vacuum leak can cause a rich/lean scenerio between cylinders.

 

[vbudwick]

Ok all good stuff. Did check inside cap no burn marks on cap. Same cylinders each time. Soaking wet. Running car with plug out and plugged in, I see spark. So yes timing of fuel spark and compression is off somehow. I'll check plug wire firing order again. Would think it wouldn't even run if they were off. It runs but like crap 6 cyl, rumbles engine, terrible. I'll check those hoses too.
Keep em coming in need help here. Somethings just off

 

[Frankie the Fink]

There are two particular wires on small block Chevys 283.327 you can switch and the car will seemingly run alright until its under load; could be the same with Ford.....at this point, if timing verifies fine I think you might be looking at a fuel distribution problem..

You can do a quick check for vacuum leaks by taking an UNLIT propane hand torch and passing it around the carb base intake manifold runners and elsewhere, if the engine idle speeds up at any point, you've found your leak. At some point it might be worth doing a "leak down" test. Again I can't say if the MSD is an issue or not.
Surely there are ways to test it from the web site or a phone call.

Finally are you ABSOLUtely its gas fouling and not oil fouling ?

 

[vbudwick]

There are two particular wires on small block Chevys 283.327 you can switch and the car will seemingly run alright until its under load; could be the same with Ford.....at this point, if timing verifies fine I think you might be looking at a fuel distribution problem..

You can do a quick check for vacuum leaks by taking an UNLIT propane hand torch and passing it around the carb base intake manifold runners and elsewhere, if the engine idle speeds up at any point, you've found your leak. At some point it might be worth doing a "leak down" test. Again I can't say if the MSD is an issue or not.
Surely there are ways to test it from the web site or a phone call.

Finally are you ABSOLUtely its gas fouling and not oil fouling ?

Yes 100% gas.

 

[Frankie the Fink]

You might just flat out be running rich, on my two four barrel 61 Corvette I had a severe fouling problem on a couple of cylinders after only about 60-70 miles on fresh plugs. Turned out the carbs were rebuilt by previous owner with wrong
needle valves and was dousing the engine with gas. The bad news is that the raw, unburnt gas is washing the oil off the cylinder walls so I wouldn't drive the car until I found the problem...just my opinion.

A word about electronic ignitions, MSD and Pertronix and a bunch of others brag about 45,000 volt spark, but the truth is you only need 15,000-20,000 to jump the spakr gap and just as SOON as the electrical potential is built up sufficient to cross the gap, spark occurs. 98% of these installation will never see nor need all that spare voltage.
Just a fact of physics.

 

[vbudwick]

You might just flat out be running rich, on my two four barrel 61 Corvette I had a severe fouling problem on a couple of cylinders after only about 60-70 miles on fresh plugs. Turned out the carbs were rebuilt by previous owner with wrong
needle valves and was dousing the engine with gas. The bad news is that the raw, unburnt gas is washing the oil off the cylinder walls so I wouldn't drive the car until I found the problem...just my opinion.

A word about electronic ignitions, MSD and Pertronix and a bunch of others brag about 45,000 volt spark, but the truth is you only need 15,000-20,000 to jump the spakr gap and just as SOON as the electrical potential is built up sufficient to cross the gap, spark occurs. 98% of these installation will never see nor need all that spare voltage.
Just a fact of physics.

Good stuff.
Cylinders 1 and 8 are lean, almost look new still. Where 7 and 3 are soaked. Rest look ok. I have been playing with carb choke lately.

 

[vbudwick]

ok latest... i have 12.4 volts at the coil, both sides of the coil. distributor is grounded properly its a MSD 8595 with a 8202 coil.
i agree with not running the car until i figure this out. going to try a different, stock coil that i have to see if that does anything.
keep em coming, still not fixed

 

[Frankie the Fink]

The MSD 8222 is the better choice, its designed for high vibration and heat and its black....
It has the same 0.7 ohms internal resistance, if you take the label off with some Goo Gone
it almost looks like factory. However if you want an OEM factory-style coil I would just get
a NAPA Echlin equivalent. It appears the MSD 8595 is very sensitve to voltage and requires
a clean 12V to operate properly,

 

[doug7740]

I must be missing something here, if spark plugs 7 & 3 are not firing and are wet with gas and the rest look to be fine, why are you replacing the coil? If the coil was the cause wouldn't that effect all of the cylinders?

doug7740
1955 Thunderbird Blue

 

[vbudwick]

Was trying everything. Haven't changed coils yet. Pretty confident on spark.
I am going thru the firing order again. Has to be there

 

[Ward 57]

Was trying everything. Haven't changed coils yet. Pretty confident on spark.
I am going thru the firing order again. Has to be there

If it was running before and then starting to act up I think you are chasing down a rabbit hole. Look at the controller. You say you are getting spark at the plug but not at the right time? Look at the electronic distributor and controller.
I've heard that the igniter in the distributor could be the issue. Not unheard of.

 

[vbudwick]

thanks to all that have replied. the final look over the spark plug firing order found that wires were jumping due to a bad connection, on my part when i changed the connectors. think it just worked when in the right position and not when in the wrong. plugs look good now after wire replacement.

 

[Frankie the Fink]

thanks to all that have replied. the final look over the spark plug firing order found that wires were jumping due to a bad connection, on my part when i changed the connectors. think it just worked when in the right position and not when in the wrong. plugs look good now after wire replacement.

Easy fixes are the best - good for you.