C2 SB is not running right......

[Dwight P.]

Here is the situation...

Car is running fine and out of the blue there is a miss when the engine is rev'd above 1000 RPM.
Spark plug wires are about 1 year old.(Lektrik Limited replacements)
Spark plugs have about 75 miles on them.(AC Delco 44's)
All wires and plugged checked for conections and tightness.

When the stainless steel radio shield is removed, the problem disappears. I tried placing a cloth between the shield and the plug wires, but the problem remained.

Is there some "electric bleed" going on between one of the wires and the shield?

Thanks for any suggestions,

DP

[Richard L.]

The Problem is Your 2nd Bullet Item...

If you're having your car judged, keep them on and live with the miss...

If you want to see a nice light show, raise the hood, crank your car up in an unlit (but well ventilated) garage and watch the electrical show...

When you want it to run right, replace the replacements with a good set of wires...

I had three sets of LL's on my car and I couldn't wait to get them off...

FWIW...

Rick

[Chuck R.]

Re: C2 SB is not running right......

Hi Dwight,

It's very possible that a plug wire(s) may have broken down and are leaking by.

I had a brand new set of plug wires out of the box that were junk when it turned damp. That evening it rained and when I hit the first puddle, it started missing like crazy. When I opened the hood (it was dark outside) it looked like an aurora borialis all around the distrbutor and at least three plugs.

I now liberally spray all new wires with silicone water proofing and use high temp di-electric grease on the caps at both ends.

I'd also make sure that the wires are running through the looms as straight and uninhibited as possible without crossing over each other or touching metal. If this can't be avoided, I always put a wrap of electrical tape on the wires where they can touch metal or each other to reduce chaffing or better yet add additional looms.

Chuck

[Jim T.]

Re: C2 SB is not running right......

Dwight my original owner 68 and 70 will lose points for non original type spark plug wires if they were judged, however I do enjoy driving them whenever I want to. I have used Moroso Blue Max custom fit sprial core plug wires on my 68 since 1986 and when it came time to change ignition wires on my 70, I put Moroso Blue Max spiral core on it as well. Having used them since 1986 on my 327/350 L79 they still are giving excellent reliable service. The wires are installed like the orignals and have molded ends. No light shows under the hood.

[Jack H.]

Another thing to check...

is the wire from the ballast resistor to the coil. Sometimes, it's routed such that it 'rubs' against the lower lip of the distributor shield, wears through the insulation and then randomly shorts to the shield robbing the ignition of electrical power...

[G B.]

You do not want to know...

..how many "properly dated" reproduction plug wires I've had to replace to get engines running right. Now it's the first thing I ask about when a car owner says his engine is missing. The second thing I ask is why they're using that crappy GM ignition shielding.

I install a Delco 508N set that costs about $25.

[John D.]

Re: You do not want to know...

Also get rid of the AC44's. They are too cold today. And if you have a replacement coil that may be a problem also. Now you guys have me scared Jerry about the repro wires on my 63. I bought them when they first came out on the market. Long time ago?? Engine appears to run with no miss though. Idles at about 875-900. Has some good aftermarket Echlin points and condenser and a h NOS D310 cap. Has a NOS coil and a NOS ballast resistor but does have the repro wires. Oh well last week one of the nextel cup boys was going about 180 on only 7 cylinders. Meanwhile when you break down Jerry a little lite under the hood helps. It is almost Christmas you know. Got your order. Thanks, John

[Michael H.]

Re: You do not want to know...

John,

If your car runs properly and doesn't foul plugs, I wouldn't automatically switch to a hotter heat range just because someone told you it was a good idea. If AC 44's stay reasonably clean and function properly, leave em in.

There was a good reason why GM engineers chose the heat ranges listed in the service and overhaul manuals. They knew a few things about spark plugs and their behavior in all of the new model year engines that they tested.

The secret is to select the coldest plug that will survive in the conditins in which it operates in. Automatically selecting a hotter heat range is both unnecessary and unwise in most cases. If the recommended heat range plug fouls rapidly, there's likely something wrong with the fuel mixture or possibly higher than normal oil consumption.

A spark plug of the proper heat range may accumulate some deposits or soot in slow in town driving but as soon as the car reaches highway speed, these deposits flaked off the insulator. However, if the heat range is too hot, deposits melt onto the insulator, become conductors that short the plug and will not burn off. Along with the misfire, the deposits become red hot and cause pre ignition which will eventually cause more expensive sounds than just an annoying rattle.

The use of unleaded fuel today also reduces the amount of carbon buildup on spark plug insulators.

If all is well in your engine and your FI is functioning properly, and I'm sure it is, you should have no problem with the 44's that you are using. I've had the same set of AC 44's in my tan FI 63 for at least the last 15 years and it didn't miss a beat after aprox 6000 miles of around town and highway driving.

Same story with my 425 HP 66 car. I've used the recommended 43N plugs for the last 23 years and they function perfectly for at least 5000 miles. If a 425 or 435 HP car needs 45N plugs with todays fuel, there's likely an oil consumption or mixture problem within.

It would have been easy for those engineers to simply recommend 46's for all cars/all engines but because they knew a lot more than we do, they selected a proper heat range for each application.

[John D.]

Re: You do not want to know...

Michael, It's the gas today that is causing a lot of the spark plug problems. If you use good fuel today you can use the AC 44's providing you are doing a lot of open road driving. Most of the owners don't drive their cars that much anymore. Where I live you can hardly drive a tank on the streets without getting killed or slammed into. The traffic is terrible and most of the time you are stalled in long lines. Then the 44's would be in trouble. One thing that I am sure that you know is too much is said about the plugs and not enough about the ignition coil and other ignition componesnts. For the show cars, the seldom driven cars, and the cars that are just used for short hops you can't beat a nice set of AC 46's Mikey. Also for the oil burners a nice set of extended tip plus sure does help. Although you can't always run the ext. tip plugs for fear of hitting a piston. I advise my customers to stick of set of AC 46's in and forget about it. If they foul those then they have some problems. Course the price of those 46's at the flea markets is sky high. But you can get some good deals on ebay. If you see the name bidder 1 that's me. John bidder 1. Jerry is bidder 2. What number are you??? Jr.

[Michael H.]

Re: You do not want to know...

The junk that builds up on plugs today isn't a conductor like it was years ago. White ash is a lot different than the lead deposits from the leaded fuel era.

Won't see me bidding on any AC 46's. You can have em all.

[Mark W.]

Re: Another thing to check...

I agree with Jack. I have a '66 L79 and I had the exact same situation a few years ago. At idle and lower speed the engine ran smooth, but if I put my foot into the gas, it would start missing, coughing and running terrible. I checked everything I could think of and then checked them again, but couldn't find the problem. Finally, I saw where the distributer shield had been rubbed the ballast resistor to coil wire and I could see bare wire. What was happening was the shield was rubbing the wire, but only when the engine was under load, causing it to twist and come in contact with the now bare wire and causing the misfire. Once I fixed the wire, the problem ended and has run fine for the past 5 years.

[Verle R.]

Re: You do not want to know...

"Where I live you can hardly drive a tank on the streets without getting killed or slammed into. The traffic is terrible and most of the time you are stalled in long lines."

John,

You just convinced me I don't want to live where you are, why don't you move out here and we can go for drives most of the year.

Verle

[John D.]

Re: You do not want to know...

Michael, Glad you don't like the AC46's. Hate to be bidding on them and see your number. Heard it was bidder3. Seriously the AC44's were a good plug in their hayday but in 2006 they are not the answer for the old fuel cars unless you DRIVE them. Just putting around and starting them on occassion doesn't give the Ac44's a heartbeat of a chance of surviving long. If you don't like 46's then try the AC 45's. Even the R45's aren't bad. Dale Pearman and I used to talk about plugs a lot. He didn't like the R plugs as he said they weren't hot enough as the real deal. But to keep out of trouble I recommend 45's or 46's. If you like 44's that's great cause you know I always RESPECT your answers more than most people in this world. Also appreciate you sending me the 20 page article on spark plugs. Nice information Mikey. You have more info at your fingertips than the public library. John

[John D.]

Re: You do not want to know...

Verle, I slow them down around here driving a big Yukon XL with a monster hitch receiver sticking out the back that sticks out over a foot. When they see that they don't get on your bumper. Guys say why don't you drive your 63 more. I said scared to unless it's Sunday morning. John

[Michael H.]

Re: You do not want to know...

I agree, if a car is only driven off-on the trailer, 45's would be my choice also. My point was that you shouldn't recommend 46's for people that actually drive their cars. If 44's or 45's won't stay clean on cars that are driven with no lead fuel, there's something else wrong.