Help needed for diagnosis - pictures inside

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Well, you installed an MSD box asking for hotter spark, yet the plugs aren't capable of the hotter spark due to the .035 gap.

Have you run the plug wires again to be sure they are correct? They are easy to mix up on a SB Mopar.
 
I worked on a car over summer that behaved as described exactly. Engine would not tolerate ANY
preload on hyd lifters. Adjusted to 0 clearance ran fine. Lifters were Comp Cams Race Hyd.
Engine was SBC. Replaced lifters with "standard" type. All is well. Cam companies claim to make
their own lifters, but I have my doubts. I think those "race" lifters were probably a run of parts
that were machined improperly in a third world country, bought at a bargain price, and
marketed as a "race" part. Waddaya think? Am I crazy?
 
madmoparmick said:
I think compession test would have seen that, though
Click to expand...

That's what I assumed as well when I suggested the rocker adjustment. Although it doesn't hurt to double and triple check things like that in cases like this.

Somethings obviously not happy.
 
Start simple. Check wire routing to ensure the correct wire is on its coresponding plug.
 
Bad Sport said:
Well, you installed an MSD box asking for hotter spark, yet the plugs aren't capable of the hotter spark due to the .035 gap.

Have you run the plug wires again to be sure they are correct? They are easy to mix up on a SB Mopar.
Click to expand...
I have checked the firing order too many times. Lol
 
Am I the first to notice that the 2 spark plugs in question also have 'dirtier' looking threads on them? I had a problem with my spark plugs seating on my 408. I could actually see soot on the ends of my spark plug boots. At first I thought it was coming off of the exhaust but when I looked closely I could see that it was only the plugs (and the end of my spark plug boots) themselves that showed soot.

View attachment IMG_1795.jpg

I switched to a tapered plug design and the problem (which was similar to yours) went away.

Some of my plugs had no issues, but I had a few that would foul. I started out running ACCEL Copper Core 784 plugs and switched to
CHAMPION Copper PlusRS12YC.
 
How many miles on this new motor?

How many times/miles have you changed the plugs since first starting the new motor?
 
Something else came to mind. One time I wired the magnetic p/u wires from the Chry. dist. to
MSD box backwards and motor ran funky. Possible?
 
madmoparmick said:
Something else came to mind. One time I wired the magnetic p/u wires from the Chry. dist. to
MSD box backwards and motor ran funky. Possible?[/QUOTE

Msd was installed when I still had the previous motor in it.
Click to expand...
 
1967 'cuda said:
Am I the first to notice that the 2 spark plugs in question also have 'dirtier' looking threads on them? I had a problem with my spark plugs seating on my 408. I could actually see soot on the ends of my spark plug boots. At first I thought it was coming off of the exhaust but when I looked closely I could see that it was only the plugs (and the end of my spark plug boots) themselves that showed soot.

View attachment 1714760611

I switched to a tapered plug design and the problem (which was similar to yours) went away.

Some of my plugs had no issues, but I had a few that would foul. I started out running ACCEL Copper Core 784 plugs and switched to
CHAMPION Copper PlusRS12YC.
Click to expand...

I will take a look at that.
 
madmoparmick said:
I worked on a car over summer that behaved as described exactly. Engine would not tolerate ANY
preload on hyd lifters. Adjusted to 0 clearance ran fine. Lifters were Comp Cams Race Hyd.
Engine was SBC. Replaced lifters with "standard" type. All is well. Cam companies claim to make
their own lifters, but I have my doubts. I think those "race" lifters were probably a run of parts
that were machined improperly in a third world country, bought at a bargain price, and
marketed as a "race" part. Waddaya think? Am I crazy?
Click to expand...

Think you're on to something , then when the part goes bad they claim you raced it racing is hard on parts , no warranty . Plus they get to charge more ,it's a go fast "racing " part that will make any car fast .
 
Looking over thread and I see you DO have adj rockers, and you DID change cam (and lifters I'm sure)
What you're going through sounds exactly the same as what I did. You should try adjusting lifters to
zero clearance- no preload. I'll bet that's the problem.
 
Simple questions:
1. The original post tells of a bad miss. Is this erratic idling or a strong miss on one cylinder?
2. Does it clear up with higher RPM's, like 1500-2000 RPM?
3. I see some crush on the plug rings, but are you tightening them to proper torque? I turn them 1/4 turn after lightly seating. (Cast iron heads.)

If it is a one cylinder miss, then after re-setting gaps, pull the plugs wires one at a time to ID the missing cylinder. The dirty plugs may be indicating one but you need to isolate it. Once isolated, then you can do the usual tests with tweaking the valve adjustments on that cylinder, checking for free valve movement, spraying WD40 at the intake runner for a leak, etc.

This can be a lot of things, so you're just gonna have to start eliminating possibilities.
 
Have you re-checked your firing order. Dist cap for any cracks or arcing?
 
duster360 said:
I will take a look at that.
Click to expand...

Mike at MRL told me that he'd never run into problems with the plugs failing to seat properly but that my heads would accept both tapered and flat seat designs. I had tried tweaking the carb, spark plug heat ranges, timing, distributor curve and changed wiring but unless I kept the rpm up, the engine would load up on fuel. Zero issues after changing plugs.
 
Thanks for the vote of confidance, Jerry6. I'm only crazy most of the time.
 
Speaking of PCV valves, funwithfuel, some intake manifolds have a hole in one of the runners for a
fitting big enough for a PCV system. I've had that cylinder draw oil when used for that purpose. It's
ok to use that location for power brakes, heater doors, or whatever, but try to plumb PCV to plenum
or bottom of carb.
 
regardless to where that might bring the timing, try rotating the distributor one way or the other while the engine is running to see if the engine gets smoother at idle. also, while the engine is running at idle, try spraying brake cleaner between the intake and heads, and between the intake to carb. that will tell you if you have a vaccuum leak. be carefull when you do this, keep clear, it might catch on fire.if all this fails, try setting the valves to zero-lash, as mentionned before ,this will tell you if one or some lifters dont work properly. this might sound stupid, but you have ajusted the idle mixture screws, havent you?
 
7e5hangten360 said:
regardless to where that might bring the timing, try rotating the distributor one way or the other while the engine is running to see if the engine gets smoother at idle. also, while the engine is running at idle, try spraying brake cleaner between the intake and heads, and between the intake to carb. that will tell you if you have a vaccuum leak. be carefull when you do this, keep clear, it might catch on fire.if all this fails, try setting the valves to zero-lash, as mentionned before ,this will tell you if one or some lifters dont work properly. this might sound stupid, but you have ajusted the idle mixture screws, havent you?[/quote

I am going to swap to a different style and if that don't work I am going to set the valves to 0 lash as you and another others have suggested and go from there.
Click to expand...
 
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