I'm running some Hedman Elite 1 5/8" LT headers (Hedman 68487). Fitment is great, but my #3 spark plug boot is really close to a primary. I thought the gap was big enough, but the boot moved a little bit and melted on the header, so it now arcs there. I thought of putting a fiberglass sleeve (DEI makes some) on the boot to protect it from the heat, but the gap is small enough that the sleeve would be touching the header, defeating the purpose. Plan B was to find some shorter spark plugs - even 1/4" more gap would allow the fiberglass sleeve to fit. I did a ton of research, and I found a Motorcraft (SP485) and Champion (CHP 71) plug that were supposed to be about 1/4" shorter on the insulator side. I bought the both just in case, and when I got them home I found they're exactly the same length as my existing plugs (Autolite AP3923)!

I've heard NGK and Bosch plugs tend to be shorter, but I'm not about to just buy one of every NGK and Bosch plug the parts store has in stock to find one that's shorter. Any suggestions?

If I can't find a shorter plug, I see two options: dent the headers, or get a wire with a ceramic boot. I have to return the headers for replacement under warranty, so I don't particularly want to dimple them, and those wires are friggin expensive ($100+ per set, IIRC). The clearance is so tight I don't think I can leave it as-is though. Perhaps leave it as-is with a thin heat shield? Maybe some aluminized sleeving or a thinner fiberglass sleeve.

 

Can you zip tie the wire to the bracket to keep it away? Also would a straight boot work and go around the back of the bracket? ACCEL makes a shorty plug.

 

I had problems with my hedman headers melting plug wires. I routed them carefully, used the boots and carried spare wires. However I still had issues and would burn a plug wire at the worst time, like on a track day. It seemed like the temps under the bonnet on a hot day with lots of stop/start traffic would be enough to compromise them even. I bought the ceramic accel wires and some Morosso wire holders I saw someone else using. I wish I did this from the start. I've been running them a year now and they have been faultless. Yes, the ceramic wires are expensive but then so are several sets of stock wires and boots. And I can drive my car enthusiastically and not worry about ignition, that's worth £100 all day long.

Attachment 48342686

 

While the wire is melted in the pic, that was my own fault and is an unrelated issue. The little wire separators I got do a pretty good job of keeping the wires off the primaries - the issue is the boot, which can't really be positioned/rotated/adjusted any which way so it's away from the primary. I came across those Accel plugs, but curiously they don't seem to be any shorter than anything else. I measured pictures of them and a bunch of other 0.75" reach plugs to compare insulator length, and I found the plugs I have in there are about as short as they get. A straight boot could work, but I'd really have to bend it to keep it away from the header. How much can you bend them?


("Overall" measured from tip of terminal to end of threaded section, "Insulator" measured from end of threaded section to flat of plug beneath gasket, and "Threads" calculated by subtracting the two. Assumes "Threads" is 0.75in in all cases. Estimated +- 0.1in accuracy.)

Glad to hear some feedback on the ceramic wires. I was wondering if they really worked. Thanks!

 

Accel makes a specific shorty plug. All their other plugs are normal length.

 

Yeah, the two I measured are listed as shorty plugs. Are these not the right ones?

https://www.holley.com/products/igni.../parts/0414S-4
https://www.holley.com/products/igni.../parts/0416S-4

 

I had the same kind of issue burning a boot or two with my Headman headers. I now run Pertronix ceramic boots on MSD wires, custom fit. I bought bulk MSD 8.5 wire and made mine and they work GREAT! You will not have to worry about burning a boot again. Ceramic boots

 

Interesting! I didn't realize that you could buy just the boot - that seems like the way to go. It would be even better if I could just cut off the burned part of this wire and use that boot, assuming it's long enough. $13.50 for a single boot would be a lot nicer than $120 for a whole set of wires.

 

Yeah know, I didn't know that you could get them in single packs and an eight pack. I thought you had to buy the wire sets which I almost did until I stumbled onto these. WOW! Awesome! Just what I was looking for. I planned on replacing my ACCEL 8.8 wires anyway, so the timing was perfect and they really work great. Even if they sit right on the header tube, they don't burn unless your tubes get to 2,000* F? At that point, I think will have more things to worry about than the boots burning. Good luck and hope it works out good for you as well. Make sure you have a pair of double crimp pliers. I think those come with single crimp terminals if I remember correctly, When I bought the MSD wire, I also bought a 50 pack of MSD double crimp terminals which I like much better, nice solid connection. The choice is yours.

 

Hmm, hadn't thought about needing crimping pliers.

I'm pretty ignorant about electrical hardware, and Google hasn't been much help. As I understand it, there are two types of crimping pliers: and crimp, where single crimp has an oval-shaped jaw that does not penetrate the insulation, and double crimp has a two-pointed crimping die that gives a more secure crimp but pierces the insulation; the former is suited to heat-shrink connectors, and the latter gives a more secure crimp on nylon-sheathed connectors. Then, as far as I can tell, there are also single- and double-crimp terminals, which is unrelated to the type of pliers: a single-crimp terminal is just crimped onto the wire in a single place, whereas a double-crimp terminal is separately crimped onto the conductor and the insulation for a more secure connection.

My understanding is that in either case (single- or double-crimp terminals) you need double-crimp pliers - is that right?

I use heat-shrink connectors for everything on my car, so I probably would rarely if ever use a set of double-crimp pliers for anything else. That makes this option go from $13 for a boot to $43 for a boot and a tool I'll rarely/never use again. I'm trying to figure out a way around that.

Edit: Actually, looks like MSD makes a $10 tool (MSD 3503) that does the job. Seems reasonable enough.

 

Like I mentioned above, the choice is yours. I don't worry about the price of any tool I have, even if I would only use it one time. If I need something to do the job right the first time, I buy it. I have collected a few tools that I know I probably will not use it again, but if I need it, I have it. The one you are looking at would probably do the job, I guess. I do not have any first hand knowledge of that tool either way. The terminals come either single or double like you stated and I prefer the double crimp and they can be a tad more finicky to install, but that's just me. After looking through the terminals that are provided by Pertronix, they are the single crimp type and the 50 pack of MSD crimps I bought are double. I just tossed the singles into a container. I measured each wire after making them and never saw more than 60 ohms per foot using the MSD 8.5 wire. I can not say that about the ACCEL 8.8 wires that I replaced which were all over three times that amount on all of them. Do I think that makes a huge difference? Not really, but resistance is resistance even with a large amount of voltage. I like having less resistance.

One more thing, I believe those boots are for 8mm wires? I have 8.5mm. If your wires are 8.5 or more, you WILL need some silicone to put on the wire to slide easily into the boots, once there you are golden. I tried some 8.8 wire into them with silicone and they worked OK, but a tad harder to get in. 8.5mm was OK for sure. Just thought I'd mention that. Good luck with your project.

Here is the double crimp pliers I have and work just fine on single and double crimp terminals.

 

Had the same problem with Hedman headers on my C3 and after burning a couple of boots up I initially tried the ceramic boots but they seemed to get too hot so I settled on wrapping just the section of the header near the spark plug with exhaust header tape, problem solved.
In fairness to Hedman their headers were okay on the original heads but the spark plug location on the alloy heads I fitted is slightly different.

 

After a month, the Pertronix ceramic boot still hadn't shipped. I called Jegs, and apparently Pertronix has been saying they'll ship them out in two weeks since April. So, I canceled the order (and Jegs was kind enough to not only waive my return shipping for the crimp tool but also refund my original shipping cost)! No one seems to carry a single, black, 90° ceramic boot, so my next option was $110 for an entire set of Accel ceramic boot wires.

I seemed to recall starting the engine with that boot not fully seated on the plug, causing it to physically contact the header. I'm hoping that if I don't do that again, 1/8" airgap will be enough, especially since my headers are coated.

So, I repaired the damaged boot with some self-fusing silicone tape, swapped the damaged wire to a spot with a lot more clearance, and just took a little more care in arranging the wires to keep them off the headers. Not a perfect solution, but it cost ~$0.50. So far (after several good drives and one hard one), the repair seems to be holding up. Worst case is the airgap isn't enough and the header cooks one more wire; in that case I'll be no worse off needing 2/8 instead of 1/8 of the ceramic wires.

 

Holy cow! $110 for a set of ceramic boot wires, what a ripoff! OK, sarcasm off.

​​​​​You had no trouble with the expense of ceramic coated headers, what's the big deal about another $110? Mods cost $

 

WOW! That sucks and maybe I got the last ones that were available. They do work for me, but may not for everyone. Good luck with your fix.

 

... but why spend $110 I don't need to for zero performance benefit? Don't know about you, but I'm not Scrooge McDuck swimming in a pile of money. I was able to drop the cash on headers because I don't spend money on stuff I don't need to, like this. There literally has to be less than a 1 in 200 chance of this working for it to not be worth trying.

Lucky you! I would absolutely have gone that route rather than repairing the insulation, and if that boot ever comes back in stock I may still end up doing that.

 

It's $110 to finish the modification. You installed the headers, now finish the job. You can't just throw headers on a machine and not expect fitment issues, this has been going on since the inception of headers. $110 bucks is too much? You picked the wrong hobby.

 

I really like my Accel Ceramic Boot plug wires on my camaro. I don't see a part number for '90 corvette though. You could try the 75-86 under the valve cover set (or even the over the valve cover set) for HEI but no guarantees. https://www.holley.com/brands/accel/...rk_plug_wires/

Worst case you can dent in the header tube(s). Pretty common practice actually.

 

But... it works...? Lol.

Thanks. I *think* the 9001CK would do the trick. I considered dimpling the header, but I'll probably leave that as a last-ditch. Even knowing it's not hurting performance I think it would just bother me having a dent in my header, ha.

 

Can't you fabricate a small heat shield and fasten it to the stud/brace mount sitting right there?