440 misfire when hot curising

[bandit67]

A very old rule of thumb, misfire, or skipping as my Dad called em, at idle=plugwires; misfire at higher rpms=plugs, still my starting point.

 

[AR67GTX]

It sounds potentially like a bad plug wire to me. Engine pulls strong with full throttle but at light throttle cruise or idle you feel an irregular miss. I would suggest warming the car up at night in the dark and see if you spot any arcing from the wires or boots. And test the continuity ohms looking for an outlier wire.

 

[nigel]

So checked the car this morning and there was nothing jumping out at me. Pulled the cap on the distributor and the contacts all had black/brown marks on them. Cleaned it and reinstalled. Started the car and it ran rough. Was hard to pull away. Limped it for a short drive to the interstate and it missed like crazy. Once I got a clear run I hit it hard and it pulled like a train. Didn't miss a beat. Once up to 60mph if I lightly touched the throttle it missed but at full throttle it was perfect. Bringing the car down to 10mph off the interstate it misfired like crazy and even backfired. Yet again give it a good hit and it pulled perfectly. Limped it the rest of the way back to my workshop and when in park it idles perfectly. Rev it in neutral and slowly bringing the revs up it also acts perfectly. Going to pull the plugs and see how they are. Have a new set on the shelf so I'll install them

 

[1967coronet]

So checked the car this morning and there was nothing jumping out at me. Pulled the cap on the distributor and the contacts all had black/brown marks on them. Cleaned it and reinstalled. Started the car and it ran rough. Was hard to pull away. Limped it for a short drive to the interstate and it missed like crazy. Once I got a clear run I hit it hard and it pulled like a train. Didn't miss a beat. Once up to 60mph if I lightly touched the throttle it missed but at full throttle it was perfect. Bringing the car down to 10mph off the interstate it misfired like crazy and even backfired. Yet again give it a good hit and it pulled perfectly. Limped it the rest of the way back to my workshop and when in park it idles perfectly. Rev it in neutral and slowly bringing the revs up it also acts perfectly. Going to pull the plugs and see how they are. Have a new set on the shelf so I'll install them

See what the plugs look like.
All tan ? All grey ? All black ?
Wet or Dry ? Oil or carbon ?
Keep track of what cylinder each plug is from.
One old test for bad plug wires is to fire it up lights off in the shop and use a spray bottle to mist some water on the plug wires.
Bad ones should show up.
Or be like my brother and just handle each wire while holding your girls hand ( ;
Plug color can tell alot about what's going on. If its just screwing up a couple it's prob ignition, if their all wet and black or all grey/white it's prob fuel / carb problem.

 

[nigel]

I'm in the process of taking the plugs out. So far they are a tan/grey colour with a small amount of black but all dry. #2 was loose and pure black. I'm having a battle with #4 to get the plug wire off and plug out. It's super tight to the shock tower

 

[nigel]

So myself and #4 had a little chat and it finally gave up the fight. I won

 

[1967coronet]

I'm in the process of taking the plugs out. So far they are a tan/grey colour with a small amount of black but all dry. #2 was loose and pure black. I'm having a battle with #4 to get the plug wire off and plug out. It's super tight to the shock tower

The #2 & #4 might have better access from under the car. Depending on headers ?
How loose was #2 ?
If you find another one or two off color plugs or loose replace or clean them up and put a new wire on them.
If you have extra cap and rotor I would slap them on as well.

 

[1967coronet]

Just seen the plug picture. Yep #2 is fouled from the looks of it and the rest are close.
That helps, Your running to rich. Your new plugs would help for a short time but until you back off the fuel they won't last long.

 

[nigel]

#2 came out with my fingers. It was shaking on the threads. After I did the cam break in I checked everything and some of the plugs had worked loose so they all got tightened home. As for richness I knew it was rich ever so slightly. Going to hook up my vacuum gauge and tune it. Thankfully new plugs are on the shelf. Unfortunately it's now raining so I won't get out for a drive

 

[Darter6]

#2 came out with my fingers.

Just might be the problem

 

[nigel]

Just might be the problem

I was thinking that but it was really bad at low throttle. Part of me was thinking it was a major issue. I had to service my daily driver so I won't get a chance to play with it till next weekend

 

[Geoff 2]

A cold spark plug will cause your problem. Should be a 5 in NGK [ the best ] or equivalent.

MSD leads. I have had this happen a couple of times with the universal make-your-own kits.
They use a a spiral wire copper conductor which has some sort of insulated coating on the wire. Sometimes there is no contact with the terminal because of the coating. I scrape the coating off to ensure a good connection & measure the resistance when finished. So check the res of your leads if using the above.

I would also lose the brand H clone & fit an Edel 750 AFB or 800 AVS2.

 

[nigel]

I'll see it I can find a peanut plug in NGK. I'm more of an NGK fan to be honest. The leads were a pre made kit I got from summit. I hope to hell they are not bad. I ran the car with my workshop door closed and lights off. I couldn't see any arcing between leads or between a lead and ground. As for the carb I got it off a buddy that pulled it from his car and put a sniper on. His loss was my gain because he's had nothing but trouble with his sniper kit. I'm going to tune the carb and change the plugs this weekend to see how it goes. Fingers crossed it'll rectify the issue. Some other issues I was thinking was potentially a valve train issue like a broken spring. If changing the plugs sorts it I'll get some NGK plugs on order and swap them out

 

[nigel]

So ordered NGK 6630 today which has a 4 heat range and is the equivalent of autolite 23 but just slightly hotter. I tried to find a 5 heat range but was in a hurry this morning. If the 4 makes it run better I'll try order up a 5 range plug and see how that goes. Grabbed a new solid state voltage reg aswell because I have a feeling I might have a voltage issue since changing to the 130 amp alternator. Paid for express delivery so I should have them by Friday to have a bit of fun over the weekend.

As for the carb I couldn't spring the money for a new 750cfm carb. It will cost me around $1100 by the time I get it delivered to me in ireland so I'll battle with the quick fuel for the moment. If I get no joy with that I'll buy a new carb or my buddy has a proflow 4 kit for sale cheap so I might consider getting that

 

[Geoff 2]

Nigel,

I run NGK '4' s in my 455. Original spec was 5, same as Chrys 6 & 8 cyl engines. Engine idles smoother. Also have them in an engine that I tune for drag racing, has run 11.6 @ 119 at 3900 lbs with a 3.31 diff.
There a lot of engines out there with plugs that are running colder than they need to be, especially with alum heads.....

You might want to drain the float bowl. E fuel absorbs moisture. I have seen water globules in the bottom of a tin of E fuel that was only left overnight. Check for water & corrosion.

 

[nigel]

During my build when I was three weeks away from starting to motor I filled the tank. Two weeks after I filled the tank it dumped fuel on the floor. I checked the tank internals with a camera before I installed it on the car and dye penetrated the tank. Nothing showed up so I used the old tank. Foolish me. The water that the ethenol absorbed tore through the tank in such a short period of time. New tank installed new fuel lines but a used carb. I am running some lucas ethanol guard in the tank but I'll still check the carb this weekend to see how it is.

 

[Geoff 2]

Is that the same Lucas, known as the 'Prince of Darkness'.....

 

[nigel]

Well I still am on my testing period so as the lucas motto goes get home before it gets dark is something I've been living by. There's a few things I want to do with the car before driving at night and that is getting it running right and be comfortable knowing its trouble free. Friday can't come around quick enough to get my new plugs and get my game face on play with my car for the weekend. I was asked by my job if I would work Saturday. I told them I have car parts arriving Friday so they knew they couldn't twist my arm to work

 

[Scott Engelhardt]

While you are installing your new plugs, check your plug wire boots for cracks. My headers are hell on wire boots, so I went with ceramic boots.

 

[nigel]

I'm running summit brand headers and I doctored them for clearance before I installed them in the car. I'm also running heat sleeves on my plug wire ends. Had a look at them the other day and they looked perfect thankfully but I'll check them when I'm at the car today