1977 308GTB Spark plug wires and extensions

Hello Everyone,

I searched our website regarding the type of spark plug wire, wires ohm value, type of spark plugs used, red or black spark plug wire extensions and if its possible to use non Ferrari parts. There was a lot of debate and some very good science and advice given, which left me in a bigger conundrum than when I started my search for data so I do what I always do and go back to the basics and to the manufacture for information. Just a side note: If you make improvements or changes in parts or specifications, Please do us all a favor and mention all the part numbers and any numbers or data that you found ie: inches or temperatures or specs that you found. Its this type of minutia that makes our forum such a great asset.

I ordered everything new from Ferrari. Ferrari spark plug wires, Ferrari coil wire, Ferrari spark plug extensions and new NGK spark plugs (part number BP5ES I gapped them at 30K, there was some debate on using BP6 OR 7ES on other posts). Then I took the old spark plug wires, plugs and spark plug extension of my car and I ohmed everything and compared the old parts ohm values to the new parts ohm values. Below is what I found:

Old spark plug wires ohm value
Front of engine side ..... .......... Rear of engine side
1= .86K ohm ..... .......... 1= 1.4K ohm
2= zero continuity ..... .......... 2= 1.3K ohm
3= 4.3K ohm ..... ........... 3= 1.2K ohm
4= 1.5K ohm ..... ........... 4= 1.4K ohm
coil wire 60K ohm ..... .......... coil wire 10K ohm
All eight BLACK plug extensions were Ohmed out and everyone of them gave a "zero" ohm value.

New spark plug wire ohm values
Front of engine side ............... Rear of engine side
1= 1.95K ohm............... 1= 3.6K ohm
2= 2.4K ohm ............... 2= 3.1K ohm
3= 3.2K ohm ................ 3= 2.9K ohm
4= 4.6K ohm ................ 4= 2.4K ohm
Coil wire 2.6K ohm................ coil wire 2.9K ohm
All eight RED plug extensions were Ohmed out and everyone of them gave a different value but all maintained around 1990K to 2100K ohm value.

I did not ohm out the old spark plugs vs the new spark plugs. I was mainly looking at the value of the wires and I was planning on changing all of the spark plugs anyway.

Just a note, the new number 1 wire is shorter on the front than the #1 wire on the back so thats why you see a difference.

But if you look at the values "Old VS New" you can see a huge problem. Not only were some wires way out of value but one wire was not even working (causing a lot of exhaust popping). The coil wires were also way out of value.

Here is the debate. Should we use the new RED VS BLACK spark plug extensions. Even though I bought new RED extensions, I opted to reuse my old BLACK extensions. The old black extensions had a perfect ohm value on each one and even though they are 40 years old, they did not show any signs of age or abuse so I put them back in just to see if they work and since I am not experienced in these matters, I don't know what happens if you put a 2100K ohm value between a spark plug wire and a plug or what it does to the amp draw on the ignitions system. BUT!!! You can not buy old black spark plug extensions. Ferrari has superseded the old black type to the newer Red type that are used in the later 328 series. When I asked if they were the same, Ferrari said they were. But I have only my old black ones to compare the new red ones to and from what I have read on our site is the black extensions do have a very low ohm value. If anyone out there knows the difference or if its better to run the RED vs the Black extensions please let us know.

Result on start up.

I started the car on a cold 38 degree day and the car has not been started in three weeks. It fired up on the first try and sputtered a lot (probably from sitting and being cold out) but it hit its high idle and ran like a purring kitten. I let it warm up and took it off high idle. A huge difference in running condition of this motor. No popping, missing noises or back firing. At the time of this writing I did not road test the car today but of course I will and I will let you know.

I hope this information was helpful to everyone out there.

 

Nice post...

Not sure why red plug extenders would ever go on a 77. Our cars (I have two) are supposed to have black ones. As you figured out, they are different...not just the color. All of my extenders are original and show nearly zero resistance when tested and they work great. They are available NOS if you search hard enough but I would never replace them unless there was a reason. Are the Ferrari wires you bought Cavis? Probably not. So interesting that some of your new wires seem worse than the originals...although not by much. If your car runs great with all your new stuff, maybe try switching the extenders back to stock and return your red ones as they aren't right?

 

Thanks...

Just an update. I happened on a box of parts that came with the car when I purchased it from the last owner and the box happened to have a set of brand new black plug extenders. I ohmed every one of them and they all came in at zero ohms (just like the old original that came on the car). As you did, I did notice the difference that the new wires had higher ohm values than that of the old wires. Typically when wires get old or degrade the wires ohm value goes up quite a lot. I have heard that 328 wires are being sold as 308 replacement wires (but I did check to make sure that I had received the proper part number) you never know. The pink 328 plug extensions do have a high ohm value, maybe the 328 wires have a higher ohm value also and that's what was sold to me. ???