I have built a SBC and its still on the engine stand. AFR Street 195's with straight plug holes. Hooker Long Tube Headers. So I'm finding that the Spark Plug Boots are right up against the Header Tubes with standard NGK's. So I got a set of Accel Header Plugs and they are maybe a 1/4" shorter than the NGK's. The last time I used the Accel's was 40 years ago and I remember them being way shorter almost like Lawn Mower short. Since I'm not doing anything out of the ordinary what are You guys doing. I remembered reading here that angle plug heads were an issue with Headers if I was to do it again I would of used angle plug heads they look to have much better clearance.

 

Header plugs and DEI plug Wire protectors

 

I used a hammer and a deep socket to make room for the really tight ones. A little torch heat helps too. It was a set of mild steel headers, not stainless steel. Plus a lot of patience.

 

3 gaskets, msd "race" plug boots, and the boot sock heat protector things.
The idea is to get an air gap, and plug boots that can take the heat.

 

I have a High Compression 427 in my 1968 Corvette and have full length headers. With high compression it is even more important to use good covers over the spark plug boots. I use the DEI boots on all eight spark plugs.The MSD 8mm Superconductors can bend pretty far and have worked great on the 427. One nice thing is in 1968 you can reach all eight spark plugs easily from above the engine. I don't even need any special sockets or extensions.

Higher Compression raises the temperature of the combustion and makes enough heat to Burn-off the first 5-6" of the ceramic coating. It also makes the engine run at higher temperatures unless you plan for it. I use a complete original factory L88 Hood and Intake system. I have the wedding cake assembly on my carburetor and it draws all the combustion air from near the windshield base is. It is the ultimate Cold air induction system and keeps my engine from detonating with cast iron heads.

Having an air gap around the boot cover is important as on my engine when one DEI cover touches the header it burns for a while and smells awful. I have never had any spark plug wires short out on this engine.

I am using Hedman Hedders on my C3 and have been very happy with them fitting. They bolted right on without any issues. They left enough room around the plugs to work, might be a consideration in the future.

Don't try and break in the new engine using any kind of coated headers. The header Coating companies all warn of the higher temps or breaking in a motor can damage the ceramic coating. I would consider checking inside the pipes to be sure they are coated inside and out if coated at all. They offer a higher temp coating (used by NASCAR) that will tolerate higher temps without burning off the pipes.

Seems strange nobody makes a spacer that pushes the tubes away from the spark plugs. That might be a marketable item. I am using the soft aluminum exhaust gaskets between my heads and the headers and they have lasted over 25 years.

Best regards,
Chris

 

When i first put my Hookers on my 86 I still had the factory iron straight plug heads. I had the same problem,if I remember correctly,was number 5 plug. I just used an autolite race plug in that spot until I changed to angle plug AFR's. I have all kinds of room now with the angle plug AFR's. The angle plug afr heads are listed as having an "L98 angle" which is not as extreme as the normal angle plug on a set of Chevy bow-tie heads. I will say this also. when I had my angle plug afr's in the shop I also had a set of straight plug afr's that were for a Malibu i was building. I noticed that the straight plug afr heads worsen the plug location condition over factory heads because afr moves the spark plug off center in the combustion chamber. It was not a problem with the Malibu headers but I noted that a saw big problems with the corvette headers. the direction the plugs were moving was right into the header tubes.

 

Yes I had this problem back on the 86's iron heads, I had to use a plug boot sock protector from Summit, but still it would eventually burn through. I'd have to periodically inspect the two that rubbed. I might get 6-9 months before the MSD wire showed a bad spot, so the socks do work. My AFR angled plug heads fixed the issue. Never found any other workaround.

 

I found this old picture . yes,it was #5 plug you can see #5 is off the tube now with the autolite race plug. #7 on right still has a full size plug.