TIPS When making your own plug wires

I made new plug wires for my TR yesterday and wanted to share my experience. I bought the wire in bulk, for a TR you'll need about 40 feet of it! I also found the 45 deg. crimp connectors locally - for a change! The spark plug boots will only accept 7mm wires unless you enlarge the hole. I chose to leave them alone. You'll need some slippery stuff to help move things along, I used silicone spray but vaseline would be good too. To get the plug boots off you can either try and pull the old wire through and snip off the connector, or do as I did and CAREFULLY pull the wire out with the old connector in place. It takes a bit of doing but it will come out, just go slow. Also you'll need to slip off the red silicone jackets and be careful not to loose the little bands with the cylinder numbers on them. To determine the exact length needed, you can use the old wires. But I went and loosely fitted the wires on the motor and cut to length to get the cleanest install possible. Next lube up and push the wires through the plug boots far enough so you can crimp on the connectors. Strip the wires back about 3/4 inch leaving just the carbon core conductor sticking out, then bend it around the end of the wire and place the crimp connector onto the wire and pinch it good. I bought the special crimp pliers to do this job right. Then very carefully pull the wire back through part way untill the connector is just starting to go up into the boot, then use a screw driver and PUSH the wire the rest of the way into the boot. If you try and pull it all the way you run the risk of compromising the crimp connection. I then sprayed lube into the silicone jacket and slipped it over the wire and up onto the boot, and the wire is essentially done. After each wire is assembled, but sure to check the resistance to verify everything's okay. Next clean out the dist. caps, for the contacts carefully use fine sand paper or emery cloth, and see that the carbon button and spring are in good order. I had to replace one button and spring as they were nearly "disolved". I found that a Mercury Tracer cap has nearly the same button, and a little sanding made it fit perfectly. I made a new spring from a ballpoint pen, not rocket science here. Next I installed the wires onto the motor and ran them through the looms back to the dist. cap. I then did any last bit of trimming needed to get a clean installation. Insert the wire into the dist. cap and tighten the lance-screw. IMPORTANT: Even though you have verified the resistance of the wires themselves, do it again with the dist. cap too. What appeared to be a good tight connection was NOT! I had to snip and retighten 5 out of the 12 wires to get a good reading. It is a struggle to get all the wires through the rubber dist. cap cover and lots of lube will be needed. You don't want to use too much force for fear of damaging the work you've already done. All in all it's a very satisfying feeling to know you've got good connections...and you did it yourself! A bit of trivia....once done the resistance of my wires from the dist. cap contacts to the plug connectors was from 13k to about 19k ohms. I also checked the plug extenders and they were "0". Bottom line is that for less than $100 I have new wires!

Hi Jeff,

Nice work. And I know your engine will love you for it. From the sounds of your old components the engine was ready to start miss firing at any moment.

Where did you buy the wire and crimp ends in bulk?

Regards, JRV

I have been following your work here. I cant get over what a great job you did.

Jeff,
Thinking along those same lines of checking the connections you made whilst building your new wire set, I'd strongly advise doing the same with a new OE wire set. If I had taken my own advise....and so many years of experience working on these cars, I would have done the same test on the new OE wires I purchased for my BB.

Likely, this would have saved me much aggrevation in trying to determine why the car ititially ran so poorly after the engine rebuild.

Who would have suspected a "bad" OE wire set, right out of the box...HA!

Excellent post, Jeff.


Regards,
David

As I am going to make a set of wires, this EXCELLENT post is timely.
Thanks a million!!

Looks really nice – which leads me to my question – Has any tried to squeeze 8mm wires into a old marelli distributor cap? Do TR s have marelli caps?

Also, is there a source for red, wire wound (like the original 13kOhm/foot) 7mm ignition wire. I cut my number 2 wire about an inch shorter than I should have. It has been bugging me for 2 years. All I need is the Red inner wire, the white silicon sleeve is fine.

Thanks

Aaron

Yes....TRs do have marelli distributor caps. If my memory serves, I think 8mm wires will fit into the marelli caps. I would have used 8mm wires except that the spark plug boots would not accept them. I tried every which way and just couldn't get it to work out.

Aaron...does the wire you need have to be red or can it be another color? Since the wires are covered with a sleeve it seems that colors don't really matter. So you could buy wire from a number of sources.

Jeff,

As far as the wire color – actually no, the wire does not need to be red, but being the nerd I am, I probably will not go to the trouble of changing it unless it matches the original wires. I have this thing about consistency, which exceeds necessity.

What ever I put in will need to have similar empedance/resistance. I bought new wires when I rebuilt the engine in ‘02 and they will hopefully be fine for a few more years, it is just that one wire that makes a tighter turn and does not look as pretty/consistance as the TR set up. As I said, it works fine, just degrades a smidge from the overall picture.

The C4 uses straight in plug connectors which are easy to fing and the new 8mm wires are much more durable and flexible. My thought in the future is to switch from Ferrari original to the new stuff. My only concern with this plan was 8mm wire compatibility.

Thanks,

Aaron

I am using 8 mm wires on my 308 and they just barely fit into the stock caps with the use of dielectric grease.
DJ

Spasso,

Thanks for the input, you’re the first person that has actually done it and thus put my question to rest.

Aaron