Running on 7 cyl.

[RotaryRocketeer]

1976 one ton single cab with a 350. Vortec heads, RV cam, Accel HEI, Performer RPM, Edelbrock carb, unknown long tube headers.

Checking fluids after work today before the drive home, I noticed my #7 spark plug wire was touching its respective header so I moved it forward a bit. When I did this, the plug moved with it. Loose as all get out. So my buddy was hanging out talking with me and we decided to go to his house to tighten it (he lives way closer to work than I do.)

Got there and tightened it after a huge hassle. He doesn't have anything with headers, so the tool selection wasn't ideal for the job. Truck was running like a well balanced top beforehand, and now it feels like it's running on 7 cylinders and sounds like it too.

Made it home and figured that the #5 and #7 wires were too close to one another and arcing, causing #7 to fire 90 degrees early. Hopped in for a test drive and guess what. No change. Looking for a little input here. It woke up as a monster this morning and went to bed as a hot soft turd. Any help is greatly appreciated.

[oldpurple]

Any chance you mixed up #5 and #7 plug wires? I have done this before and it runs surprisingly 'well'....

[Dead Parrot]

Depending on the hassle and tools involved, is it possible you cracked the plug(s) in question while getting them in tight? A single plug loose but mostly in a hole will still fire and produce power. A cracked plug might not.

Won't help current problem but might be worth a trip to Harbor Freight or Meridian Tools for a low cost set of tools for your particular setup and a tool box/bag that you can keep under/behind the seat. That way you always have a set of tools needed for minor on the road repairs with you in the truck.

[rwhit57]

Even touching plug wires shouldn't arc. They probably are either cheap wires or worn out. I would replace the wires and plugs and i bet your problem will be solved.

[Pontiac1976]

I would think the wires are getting dry out. or knocked one out place ( not seat right )
run it at night in dark place pop the hood see if you can see any arcing. If not pop one wire off at a time see if it get wore that one should be good one. If does not get wore that wire or plug for the cylinder has to be checked.
( Tip with headers, make your wires last longer. Clean them with Silicone Spray. Then bath in lite coating let soak in after night lite dry wipe them re in stall (about ever 3 mounths). They will look new
should not arc. Un less there really old have cracks in the rubber salving (If the rubber does not feel smooth it drying out. If you do not let get to dry you can bath them per long life a little more. ( this can get you out of a jam sometimes ).

[RotaryRocketeer]

Thanks for the replies all. I was away at a concert for the weekend, and am just about to get home and check things out. I'm with Parrot, in thinking that I broke the ceramic insulator on that particular plug. I jammed a 5/8 socket in there to tighten it, because that's what I had.

The wires look good enough and I couldn't see any arcing in the dark when I checked the other night. Picked up a through-socket set and plugs/wires on the road yesterday. Will report back with results.

[RotaryRocketeer]

Thanks to everyone for the suggestions. It was a broken insulator on the #7 plug. Threw a new set of plugs and wires in and all is well. Back on the road and running great!

And to anyone running headers that doesn't have one already, the Pittsburgh (cheap, I know) through socket set from Harbor Freight is a life saver. Best $18 I've spent in a while. Thanks again!