• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Chasing-down Elusive Miss. Wires?

KingCapt

Active Member
Local time
2:44 PM
Joined
Jun 19, 2022
Messages
43
Reaction score
30
Location
York, PA
I'm running a 400 4bbl in my '67 Satty. I have an unidentified miss across the rev range from idle onward. Background: Good compression in all 8 cylinders. Running the Mopar Orange Box. Eddy Carb thoroughly gone through. New NGK plugs, cap and rotor. My next step is wires...Currently running Taylor Pro 8mm wires. I'm looking for suggestions on potential issues, recommended wires, custom fit, or a B motor specific set. Interested in learning and finding the issue. Thanks in advance.
 
Check the distributor cap for cracks or corrosion. I once found corrosion inside one of the distributor cap sockets, after replacing most everything. I was told the cap was new, but apparently water had gotten in one socket. It was totally green inside that socket and didn't show on the wire. One in a few thousand, but worth looking.
 
Personally I'd try a chrome box if you can find a good one. If it proves to be the ignition box, I'd move on to an MSD and never look back. Sometimes people will hide the MSD to preserve the Mopar look. I didnt bother after I went through what you are going through. You may want to get in contact with Halifaxhops (member here) and see if he can test the orange box you have before investing too much into troubleshooting.
 
Before spending money, run it at night in the dark and see if there isn't a bad wire or the cap.
 
Is this a steady, Continuous miss cold start-up thru fully running temp Or is this more random Intermittent miss issue or only at certain engine temps, speed or loading ??
 
Am I "missing" something ? ....If a Continuous miss at Idle (he said idle thru rev range), don't we back a distributor Cylinder wire off one by one & identify which cylinder (s) are Least Functional by noting Rpm Drop ??
 
^^^^ Good call. Short out the plug on one cyl at a time & see if one cyl makes little or no difference to how the engine runs.
 
Hi Geoff,...Just a simple, quick, Zero cost test I do at the Dizzy wire nipple/insulator end.... Slowly Backing & distancing wire off cap tower, a Good ignition spark Should arci & "snap" for a good Inch until it dies & Rpm Drop noted....Works Best with Auto Trans in gear & rev'd Steady held on converter Load by Reliable helper....Any issue from general Weak spark to 1 or more weak cyls quickly located...
 
You likely checked this but:
Firing order?

It's not clear to me if you had the miss and changed the plugs and still have the miss?
Another thing to do is just listen to the exhaust if you have true duals that will tell you which side.

I would certainly try another Ignition module the newer orange ones seem to have a poor track record.
 
Thanks everyone. Couple things: This condition existed before I started going through the carb and timing, which were my first steps. It does run better. Carb was poorly jetted and floats were not set. The new plugs show a lean burn, but uniform across cylinders. Exhaust is true duals. The stumble resonates across both banks. Engine exhibits signs of "searching". I suspected an intake leak. My brother (mechanically gifted engineer) says he thinks ignition, and that wires are next step. I got a second opinion from local garage guy that's been collecting and resurrecting old Mopars for 30+ years. He supports the "wires" step of replacement. I will read through all the comments and follow-up. Thanks guys. Appreciated.
PS: I contacted Ray at Halifaxhops and will get his take.
 
Before spending money, run it at night in the dark and see if there isn't a bad wire or the cap.
Good idea and spray with water also. You will be amazed how wires will leak voltage through the insulation if bad. Spray bottle not a garden hose FYI.
 
Taylor wires are usually good (unless burnt).
You could get a cheap set from RockAuto as a test.

I'm still leaning towards the ECU. But checking the reluctor gap might be a good idea as well.
I had an orange box fail above 3500 rpm years ago it would run fine until you went full throttle.
Spent a month or two on and off checking everything.
Finally tried an old cheap parts store ECU and it spun to 5,000 RPM no problem.
 
1 about 25 yrs ago I worked on a 68 440 tnt with an odd miss.. turned out to be a broken valve spring
2 about 6 yrs ago I had a 65 mustang in, ran fairly well and I was tuning the mixture screws. As I leaned it out, one plug wire started arcing to inner fender. More lean, more reliable Crack Crack Crack... fatten it up, went away completely. Could use that as a diagnosing trick..
3 headers or manifolds? Could try a temp gun on the ports/pipes..
 
Another possibility. If the reluctor air gap is tight & the rel is slightly out of round, one of the teeth might be making contact with the coil. No spark on that cyl.
 
If you were closer We could hook up this old Girl.

IMG_0324.JPG
 
I thought this was going to be about a spokes model for Fire-Core brand.
 
I thought this was going to be about a spokes model for Fire-Core brand.
LOL. Not yet. Ray at HalifaxHops has given me a list of things to pursue. Depending on the outcome, I may have him scope it.
 
Another possibility. If the reluctor air gap is tight & the rel is slightly out of round, one of the teeth might be making contact with the coil. No spark on that cyl.
I'm checking gap on 4 ribs (quarters) tonight. If post is bent/out of round I'll know.
 
Auto Transport Service
Back
Top