Spark Plug Extenders ... Opinion

Oldddddd thread butttt just snagged my 308 and realized i have “black””extenders. I have been having some misfiring issues. Looking at replacing them. Based in this site it looks like my 85 QV needs the red ones (longer?)


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I have both red and black extenders in my collection. Both are the same length. I don't know if 2V and 4V cars take different lengths or not, but I don't think you can rely on color to determine anything.
I suspect that at some point there is a difference where they switched to RFI suppression wires, plugs and extenders, so perhaps the later extenders have some amount of resistance and the earlier are zero ohms.

 

One advantage to red is if they crack or start to arc you can see it.

 

Any tell tale signs of the arcing?


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Brian Harper is right both red and black extender are the same length, although one of the Ferrari tech told me that the 328 uses the longer red extender, longer then the QV extender, can anyone confirm it?

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Look at the pic i shared.. it looks likr there is a red and black option that dont vary on uses but then there is a red one for the 288 and 308 QV... must be something different


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I saw the pic this is why I’m kind of confused, my 84 QV has the black extenders and has been since new and my car runs great, smooth, and no misfire at any rpm, but your pic shows that a QV calls for the red one.

 

When I had my 77 308GTB I inspected the spark plug end of the extenders I noticed that the rust had eaten away at it and I was missing a bit of it. Did it go down the spark plug hole?
After that I always inspected the ends before I blew out the spark plug well in the head with air. I also always covered the engine with some plastic before washing the car.

 

I don't have them anymore. I designed them out with spark plug wires that reach down into the hole without the pesky extenders. Chinese knock offs last no more than 6 months so I have had it with them.

 

I still have the originals on my 85 QV. They are black.

 

I think the first sign is usually a little stumble in the idle. But what you would see, if you see anything, is a black spot approx 20mm from the bottom of the extender. On a red extender this black spot might be so small it is hard to find. Of course finding a tiny black dot on a black extender is going to be even harder.

Next time I make new wires I think there's a good chance I'm going to follow Mitchell and run the wires through the rubber plug and attach them directly to the spark plug top.

 

And very quickly, it gets to a misfire permanently.

 

I am going from memory since it has been over 20 years since I swapped them. The orange extenders for 328's are slightly longer. The originals on 308 QV were resistive, about 2k and they would go to hi-resistance and cause misfire. The 328 version has 0 resistance and will not go bad.
Use the 328 version.

 

The only problems I had with misfires on my 85 QV were due to the Cavis spiral wound wires breaking internally. I have no idea if the extenders are resistive or not, but the spiral wound wire are.

 

There are other threads on the topic, such as:
QV spark plug wires and extenders - Black vs. Red

Most modern spark plugs themselves now have resistors built into them, so it doesn't matter whether you use the black or red type. The bajillion volt spark impulse doesn't really care about a few k of resistance. Per the photograph already posted they are both the same length.

 

With all do respect. It does care when the resistance go from a few ohms to infinity (open). The extenders with built in resistance can go open.

 

I believe the intended thought was not high resistance to being equal to open resistance.

 

So what is the ideal extender and plug combination for my QV?

 

If I remember you also have an 84QV, look at my post #32 and Johns post #35 our cars originally came with the black extenders without any issue so I believed yours did too, unless your spark plug wires were changed as some point that didn’t have the right resistance then neither black nor the red will work, so if you ask me black is what it’s supposed to have on your car.

 

High resistance is = to open or high resistance.

 

Incorrect. High resistance is relative to the design of the circuit; if there is *any* measured resistance, it is not open. Open = infinite resistance, meaning (as named) an open circuit.

 

Thorn, Let me express it this way A very high resistance is = to an open circuit (infinite ohms resistance). We are talking about the resistance thru a spark plug extender. If you measure the resistance from one end of the extender to the other end of the extender and it very hi ohms ( hi resistance) it is = to being open. The stock design was for around 2k ohms of resistance thru the extender. As an Electrical Engineering grad from UT and 34 years as a BSEE, I can assure you this is correct. Lo or 0 ohms = a short. Hi ohms ( infinity) = open.

 

I stated things a little more assertively than I should have. I apologize.

After some research, I decided to use for my QV 100mm 0 ohm ("black") plug extenders from Kingsborne Wire Werks (BER-4813) and NGK Iridium BPR7EIX plugs.

I like the Kingsborne extenders a lot better than the 0 ohm Mafer ones that were in the car; the spring clip for the plug is much smaller diameter so will be less likely to arc to ground. They are harder to push onto the plug however and require some care (and force) to get them to seat correctly.

 

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Id say i found the issue


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I suppose we're debating effectively vs actual. I'm simply being dogmatic, as I don't want someone hooking up a meter, seeing something that reads "OL", and assuming that a given value (say, 20K) also equals open. No offense meant to your creds.