Help!! Mac headers, plugs advice needed!

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Hi guys new here and happy to have found this site specific to the SN95 5.0L.
I have a '95 GT and in the process to upgrade the HIC but have run in to a bit of a dilemma. I bought this as a stalled project which came with all the parts to finish......he said lol. I have the GT40P heads with upgraded springs and would like to use these however two things are holding me up, the headers and the plug length. Cylinder number 4 no clearance for the plug let alone the spark plug boot. The headers are the MAC short tube 90-8690. These run very close to the AC line which I'm prepared to move. The plugs are the Autolite copper 104 with .708" reach. Not sure what I'm going to run up against on the drivers side??
So my questions are: is there a shorter plug I can use to gain the clearance and can i clearance the header with a big hammer?
Thanks
 

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Mustang5L5

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There isn't a different plug that can be used. Usually a few 90* boots on the wire ends does help as well as dimpling the headers slightly. Expect to burn a plug wire once in a while. It's the main drawback of the 40P heads and why the Ford P-specific headers sell for $$$ when they pop up for sale.
 

lwarrior1016

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Wish I could help, I’m not very versed in the pushrod stuff. I remember getting a set of “header plugs” for a 350 a while back. They were short plugs, but I don’t know if they would fit your engine or even work for you.
 
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Just an update on my dilemma, So the only issue I had on the engine was cylinder #4 plug, drivers was totally fine. So i clearanced the tube for cylinder #2 to allow a regular sized plug fit using a 90* boot with heat shield sleeve. I did find a shorty plug but its Accel P526S different plug but could work in a pinch.
Using Explorer heads requires the reach on the plug to be .708, most shorty plugs either come in .460 and .750. Not sure if one can use the .750 without interference issues, please let me know if that is doable because they are a lot cheaper.
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lwarrior1016

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I can’t answer you right lug question, but I will say, those boots that slip on the spark plug wire will cause problems. They heat soak and transfer a bunch of heat in to the plug wire. I can’t tell you how many of those fiberglass and titanium plug boots I have seen that melted straight in to the plug wire.
 

Mustang5L5

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Ah, you are running equal lenght. I’ve rarely seen that attempted with the 40Ps.


Edit. Equal, not unequal
 
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I think these are equal length based on how they are run. Yeah funny how the driver side was awesome all kinds of room and then the passenger side with 3 out of 4 great just the 4th cylinder issue. These are MAC headers??
 

Musturd

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Usually I’ve used standard shortys or long tubes with p heads
 

Daryl

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Welcome to the Forum! Quite a dilemma you have there because you certainly don’t want to have to change plugs/boots all the time. So, I thought of a possible solution thinking backwards! Instead of cutting plugs, replacing boots at whatever intervals the issue rears its ugly head, what about Musturds idea of long tubes?

It seems to me that what you’ll spend for the long tubes will eventually equal or exceed what you’ll spend for replacing plugs/boots PLUS you have to calculate in the headache factor of doing that intermittently. If it were me, I’d get an appropriate set of long tubes that work and clearance the plugs and wires, be done with it and never have to worry about it again. Then you can move on to the next headache and leave this one behind!

Maybe even sell the equal length headers you have to help offset the cost of the long tubes.

Just a thought… good luck with the project. Keep us posted and have a safe, happy and healthy New Year.
Cheers!
 
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I have thought about changing headers but going to long tube means more exhaust changes so if I did anything I would go with standard headers as long as they have the clearance for the plugs. For now I want to get this thing running to see if there are other hidden issues not apparent right now!
 

Daryl

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I have thought about changing headers but going to long tube means more exhaust changes so if I did anything I would go with standard headers as long as they have the clearance for the plugs. For now I want to get this thing running to see if there are other hidden issues not apparent right now!
Sounds like a plan. Have at it, good luck and keep us posted!
 
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Well I have the headers on and clearanced the one plug to fit, will need a modified spark plug tool to get it off and on. I will go with angled boots and sleeves to protect the wires. Headers aligned well with the exhaust so that was a bonus.
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lwarrior1016

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I’d seriously reconsider using the boots on the plug wires. They will cause problems. Get a good set of wires, msd wires with bendable boots are good, or 90° or 45° boots. If you keep it off the header, it will do better than those boot covers
 
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I’d seriously reconsider using the boots on the plug wires. They will cause problems. Get a good set of wires, msd wires with bendable boots are good, or 90° or 45° boots. If you keep it off the header, it will do better than those boot covers
I will but there is one boot that will probably be right on the header and that one has me concerned needing some help.
 

lwarrior1016

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The covers will not stop it from burning through the wire though. I actually dealt with that exact thing this morning. My buddy’s procharged ls swapeed Monte Carlo had a wire with a wire cover/boot on it. It was brand new from yesterday and melted the wire on our way to work this morning. Only got about 30 miles out of it.
 

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20170417_160039.jpg

if you look at the spark plug wire i installed heat shield fireproof jacket around the plugand wire
 

lwarrior1016

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View attachment 31724

if you look at the spark plug wire i installed heat shield fireproof jacket around the plugand wire
That’s the thing I’m talking about. Those soak up heat and melt wires. Mainly when they are touching the headers. It’s kind of backwards to what they say it’s supposed to do, but I have fixed many misfires by removing those.
 

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