Spark plug diagnosing help, please!

[moparedtn]

Welcome to "Ed's mystery motor, post #gazillion".
Those of you who have been following along know this is a mystery 440 in my '68 GTX.
The latest was I installed a mechanical oil pressure gauge; since I've heard some rather scary rattles in the engine a couple times under hard acceleration, I also presumed that the mystery chrome dipstick in this thing might be off and added a quart of oil to what I think was already 5 (stock pan, I think).
When I fired the car up to test the gauge, it warmed up as usual seemed like. I goosed it several times to watch the gauge for operation and then all of a sudden...
it wouldn't idle and ran pretty rough. I had to keep my foot on it to keep it running. Idle dropped from 800RPM to less than 500RPM, like it had dropped a cylinder or skipped timing or something.

As I continued to try to "clear its' throat", it would sometimes seemingly hit on all 8 and smooth out for a moment, then go back into grump mode.
If I held throttle to around 2000RPM, it would grumble grumble grumble hit on all 8 grumble grumble hit on all 8 grumble grumble.
Intermittent, like that.

-Recent compression test showed 130 across the board, give or take a couple pounds (yep, they're all that close).
Previous owner, long deceased, built this engine out of what looks like a '75 block with the original '68's internals. I have pretty much replaced ALL ignition, fuel and cooling systems on this car (and I mean ALL). It also has a newer fairly mild Comp Cams and lifters in it.
Typically, the engine runs well enough and I've put probably 6-700 miles on it since I've gotten it back on the road this summer.

Here's the spark plug pic:

They're the usual Champions with just a few hundred miles on them.

I don't see anything to warrant concern here. If there was anything drastically/mechanically wrong, they'd show it, right?
Y'all know a bunch more about this stuff than I do. All I know is right now, after all this work, my baby is a beached whale in prime summer cruising months!
HELP!!

 

[moparedtn]

PS - #5 looks really clean in that pic, so I spun it and took another:

 

[1967coronet]

Plugs look decent Ed, that extra qt of oil will only help you find a leak or cost you a couple or three HP win you spin it up.
Myself I would start at the basics and while its doing its ruff idle start pulling plug wires one at a time to try to locate what cyl is miss firing.
If the plug wire test does not produce , check the carb for something affecting the idle circuit. vac leak, ect.
Back to the dizzy check voltage readings ect, cap crack ? rotor fried ? I cant remember ed if you still are running points, mabey a little grease on them and a burn spot now ?
Good hunting my friend.

 

[moparedtn]

Plugs look decent Ed, that extra qt of oil will only help you find a leak or cost you a couple or three HP win you spin it up.
Myself I would start at the basics and while its doing its ruff idle start pulling plug wires one at a time to try to locate what cyl is miss firing.
If the plug wire test does not produce , check the carb for something affecting the idle circuit. vac leak, ect.
Back to the dizzy check voltage readings ect, cap crack ? rotor fried ? I cant remember ed if you still are running points, mabey a little grease on them and a burn spot now ?
Good hunting my friend.

Naw, electronic ignition conversion. New distributor, control ECU, spark plug wires (MSD), coil (MSD Blaster), etc.
I figure if one of the wires is bad, it'd show on the plug?

 

[lewtot184]

looking at the straps i think there may be too much timing,.....? plugs are dry, that's real good.

 

[mopar 3 B]

What does the other side of 6 look like. The side shown is to clean compaired to the other 7. Does that plug fire?

 

[CudaChick1968]

Grab an old Chiltons manual and open up to the inside back cover.
There's a Spark Plug Troubleshooting Chart in there.

 

[moparedtn]

looking at the straps i think there may be too much timing,.....? plugs are dry, that's real good.

Thanks, what I'm hoping too. Figured if a cylinder was having issues mechanically, I'd see it on the plug?

 

[moparedtn]

What does the other side of 6 look like. The side shown is to clean compaired to the other 7. Does that plug fire?

It's definitely the cleanest of the bunch. Wouldn't it be soaked if it wasn't firing, though?

 

[moparedtn]

Y'all keep in mind I haven't changed anything in the tune or the motor recently at all. This problem just popped up out of thin air when I was revving it after installing the gauge.
It's like I've ticked off something??

 

[WileERobby]

Start with simple things... look at your engine idle in the dark to see if any wayward sparks are jumping, check to see if the cables are tight,etc. check any vacuum hoses that may have popped off... many times its a simple thing

 

[mopar 3 B]

View attachment 352388
It's definitely the cleanest of the bunch. Wouldn't it be soaked if it wasn't firing, though?

Depends on the amount of time it sit before the plugs were removed.
You said it has had a recent compression test. Was that before or after the problem developed? Maybe a good time to check 4, 6 & 8 again. Will give an indication if something has happened to #6 and if low would support fuel wash.
Not sure why it would only affect #6 now and not before but with a plug that clean at also may not be getting fuel and show signs of no combustion.
Or I could be totally wrong but that is where I would start.

 

[moparedtn]

Start with simple things... look at your engine idle in the dark to see if any wayward sparks are jumping, check to see if the cables are tight,etc. check any vacuum hoses that may have popped off... many times its a simple thing

Thanks.
Yep, one of the first things I did was turn off all the lights and go looking for arcs.
Nada.
Will check more tomorrow....

 

[HEMI-ITIS]

Also,next time you change the plugs,go one step colder as they look hot. You would like that coloer change to be in the elbow of the strap.

 

[moparedtn]

Also,next time you change the plugs,go one step colder as they look hot. You would like that coloer change to be in the elbow of the strap.

View attachment 352425

Thinking of changing from Champion to Autolites #85, actually. Good idea?

 

[moparedtn]

Depends on the amount of time it sit before the plugs were removed.
You said it has had a recent compression test. Was that before or after the problem developed? Maybe a good time to check 4, 6 & 8 again. Will give an indication if something has happened to #6 and if low would support fuel wash.
Not sure why it would only affect #6 now and not before but with a plug that clean at also may not be getting fuel and show signs of no combustion.
Or I could be totally wrong but that is where I would start.

I'm wondering if the dang thing is wiping another cam, actually.
It originally wiped a couple lobes on a purple shaft cam it came with when I first got it, supposedly on a fresh rebuild.
If a lobe has gone flat again, reckon no gas is getting in there and would explain the cleaner (but not pristine, mind you) plug on #6.
Probably over-reacting here...
If this engine winds up being a cam-eater, it's outta here, I guarantee that.

 

[HEMI-ITIS]

Thinking of changing from Champion to Autolites #85, actually. Good idea?

I tried the Autolite racing plug,I use a regular NGK for $20 a set.

 

[HEMI-ITIS]

I'm wondering if the dang thing is wiping another cam, actually.
It originally wiped a couple lobes on a purple shaft cam it came with when I first got it, supposedly on a fresh rebuild.
If a lobe has gone flat again, reckon no gas is getting in there and would explain the cleaner (but not pristine, mind you) plug on #6.
Probably over-reacting here...
If this engine winds up being a cam-eater, it's outta here, I guarantee that.

Adjust the valves again.If a lobe is going,you'll have alotta adjustment on that rocker.

 

[Ron H]

Are you pretty certain you have an electrical problem? It could be a fuel related issue especially since the car hasn't been driven much. This could be as simple as a fuel filter and/or clean out of the carb. Depending on your carb some have a filter or screen inside the fuel line connection that could be clogged. If not then a check of the pump could be in order. Going back to electrical, since you have el ig is issue as mentioned is a check of the rotor and air gap. You can run a vacuum check if not done as another way to trace down problem. Also I ran into ECU problem on my '63...crapped out just like that after doing all sorts of checks before zeroing in on it. Just a few more cents to toss at you...

 

[petieg383]

Adjust the valves again.If a lobe is going,you'll have alotta adjustment on that rocker.

I was going to say the same thing. I like to pull the valve cover and turn the idle down about as far as you can without it stalling to look at the valves opening and closing. Make sure you cover up with a towel or something like that because some oil will be thrown around. You'll know right away if one of the lobes is wiped.

Also, when I've wiped a lobe before, especially an exhaust lobe, the engine would get pretty hot pretty fast when not moving, so that's something to look for as well. But judging by the plug color, they are all firing somewhat evenly.