Eddy head spark plug interference

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supertruck

supertruck

Unretired Old Fart stock car racer
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I have an issue with the Edelbrock aluminum heads on the 340 I'm building. I got a set of NGK plugs today and threaded them in. Before they can thread in far enough for the washer to seat, the points on the hex head where the socket goes hits the head and it won't turn. Does this on every plug. I've had a lot of experience with plugs but never this. Am I missing something here?
 
Wrong plugs, you need cad plated not black and 5/8 head not 13/16.
 
Edelbrock clearly states that on the product description for there cylinder heads.
 
Learn something every day. These NGKs were the equivalent to the Autolite 65s I wanted, at least according to the store. Shoulda checked myself. Thanks guys.
 
72Dart6pack said:
Edelbrock clearly states that on the product description for there cylinder heads.
The paperwork in the box says only 14mm threads and mentions a Champion part number. Says nothing about 5/8 vice 13/16.
Click to expand...
 


I'm sure the Champion plug number was an RC12YC or an RC9YC and the C would tell you it's a 5/8 hex and 3/4 reach.
 
If your not willing to concede on the plugs, you can always have the pistons machined down so they sit in the hole deep enough to clear the plugs...compression is overrated anyway

:poke:
 
Sorry that you glossed over important information that they gave you. I can see your next post (NGK Plugs for sale)
 
Been running Edelbrocks on 2 different engines always use Autolite 3924's...
 
man , some people need to read better. the 13/16" hex hit the head, not the plugs hit the pistons
 
supertruck said:
I have an issue with the Edelbrock aluminum heads on the 340 I'm building. I got a set of NGK plugs today and threaded them in. Before they can thread in far enough for the washer to seat, the points on the hex head where the socket goes hits the head and it won't turn. Does this on every plug. I've had a lot of experience with plugs but never this. Am I missing something here?
Click to expand...

I used the Edelbrock recommended plugs with no issues. I understand some like certain brand plugs, but proper cross reference is on them. 65'
 
I did the same thing on my Indybrocks. Thinking that all Sb's used the 13/16 plug, I bought a set only to run into the same problem. Then I found out I had to buy the smaller plug. Like a Autolite 3924.
 
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