Off idle shudder

[FRATZOG]

Another update.
Tested cap and wires against the new replacements. Not much difference
Pulled the plug out of #4 hole and took my DVOM to it. Measurment showed open from tip to center electrode.
Ive worn plugs out. Never had one go "open"

Im sure the low speed misfire was due to low voltage at idle and it would jump the gap inside the insulator to compleate the discharge at a higher rpm.
Would that be a safe asumption?

gotta run for new plugs.

Yup, had it happen before with Champions... I switched to Autolite and never looked back.

[ws27]

Frustrated!

What happened???

[Hibbing_Coronet_500]

I rechecked all plugs. Cleaned them with emery paper and ohmed them at the 200k scale and I got 4.9
All plugs ohmed the same.
Checked every wire. About 10k per foot.
Cap tested perfect.
Still shudders. Thinking a comp test is next. Gotta buy a new tester next payday.....

[Drag-Net]

While waiting for the next payday......... You mention it's a stock 383. Does that mean it also has stock 5/16 push rods.......
If so remove the valve cover off the problem side check to see if one is bent. A bent push rod means a valve is opening late and closing early, which
will cause a shutter/miss. It happen to me years ago, pulled my hair out trying to figure it out. And that was the last I used 5/16 push rods.

[67440Dodge]

And if you want to verify it's a bad plug, put it in another cylinder and check it with your IR gun. If the cooler temp moves, then you know for sure it's the plug. If it stays put, then you know it's a problem with the cylinder itself.

[Hibbing_Coronet_500]

Update.
Bought new autolite #86 plugs. New wires, Cap and Rotor.
Noted all passenger side plugs were Sootier than the driver side. Indications of over rich. ( I had idle mix screws out to 3 turns )
Driver side plugs even rich looking had a hint of tan/gold on the plug.

Started the car and it was really retarded. I indexed the distributor before I removed it to insure close timing.
I reset the timing to 8 deg before. Idle improved. ran through shudder zone. no shudder..
Hooked up vac advance and the car came alive. it idled different and sounded awesome!
lowered the set screw for the idle.
Took it out and it ran like I wanted it too.

On the highway.. Ping Ping PING. at crusing speed... hammers under the hood.
I tweeked the vac can all the way to the RIGHT with my 3/32 alen wrench.
I started backing it out 2 turns every pass I made down the 5 mile road I can do a honest test on...

Ping Ping PING..

After 10 passes, I can tell its going back to being a slug. need to do a new plug check tomarrow.. too hot tonight

Thats all I got

[ws27]

The adjustment of the vacuum advance really only helps when you have partial throttle. Do you have it hooked up to ported vacuum? It is not supposed to have any vacuum at idle. When you just come off idle the vacuum advance will be at it's strongest, as you go towards full throttle, mechanical advance takes over. You might need to cut back on total advance,

Personally, it all my years (I know, much less than others here, LOL) I don't think I have ever taken a timing light to any of my old Mopars. I really time them by sound to what ever crappy gas is in the tank.

[Hibbing_Coronet_500]

I was following MP paperwork. To the point of going all the way till the screw won't turn any more!!
Ill gladly crank that screw CCW now that you say MP messed up their instructions?
Wheeeew? Thought I was going to go crazy or sell the car.
Thank you all!!

[Hibbing_Coronet_500]

Ported vacuum on a Edlebrock 1405 is drivers side fitting? That's the one I'm using.

[Racer Brown]

Get the tank down to almost empty, then dump in about 5 gals of some real good gas.