Spark plug reach

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Craig Burriss

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Hey guys,
I’m trying to find some spark plugs that fit a 5/8 wrench because the 13/16 are way to hard to get in and out with my Schumacher headers on my 440.
My problem is that all of the 5/8 plugs have a .750 reach.
I have 452 heads that are shaved down, and flat top pistons at 0 deck height.
It seems to me like a .750 reach would be too long for these heads. Does anyone know of a 5/8 plug that has the .375 reach?
Here’s a picture from when my heads were at the machine shop. You can see the thin wall around the spark plug hole. If a .750 plug were to be installed, it would stick way out into the cylinder. I don’t think it would hit anything, but it seems wrong.
97FA4DFA-CDB1-4B39-984E-B1977204098B.jpeg
 
This question is why we need to go back to about 1970, 1980, 1990 and if not paper catalogues with actual information, then the electronic versions thereof.

This sort of thing, here

https://www.championpowersports.eu/assets/II-Partnumbering-structure.pdf

In Champion speak, "J" as in J-12Y is a 3/8" reach plug, H is 1/2, N is 3/4 like small block Y is extended insulator, so a J-8 is still 3/8 reach but the insulator doesn't stick in as far, and adding an R to the front means resistor, a C to the rear means Copper

They make a CJ-*** which is "compact" for power equipment, it is then 3/8 reach but "compact" meaning smaller (3/4?) hex and short insulator. There are other combos, which is why, in this day and age, we need damn catalogues!!!

Only thing I can suggest is search around for other brands of catalogues and when / if you get a number and confirm "it is good" then interchange that to a brand you really want
 
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Hey guys,
I’m trying to find some spark plugs that fit a 5/8 wrench because the 13/16 are way to hard to get in and out with my Schumacher headers on my 440.
My problem is that all of the 5/8 plugs have a .750 reach.
I have 452 heads that are shaved down, and flat top pistons at 0 deck height.
It seems to me like a .750 reach would be too long for these heads. Does anyone know of a 5/8 plug that has the .375 reach?
Here’s a picture from when my heads were at the machine shop. You can see the thin wall around the spark plug hole. If a .750 plug were to be installed, it would stick way out into the cylinder. I don’t think it would hit anything, but it seems wrong.
View attachment 1715612411


AFAIK, you have no choice but a 13/16 hex. And that sucks.

I have never seen that “J” series plug with anything other than a 13/16 hex.
 
All this came about due to a note about my Kahr .40

From the manual:

"Insert the magazine into the magazine well at the base of the grip until the magazine catch engages fully.Pull the slide fully to the rear and lock it back us-ing the Slide Stop. Next push down on the Slide Stop to chamber the first round into the barrel. Do not chamber a round by pulling back on the slide and letting go of the slide. This may cause the slide to not go fully into battery.

Note: Do not load an individual round into the chamber and then close the slide. This can dam-age the extractor. Only chamber rounds from the magazine as described above."
========================================================
I used to do that very thing. But I have not had trouble simply cycling the slide on a full mag, but I like to have it "fully loaded" as they say, so I load the first one from a full mag, then remove the mag, and insert one more round. Of course when swapping mags it's not a problem, as obviously, the slide locks open, you stick in a loaded mag, and release the slide lock.


I've had other semi auto pistols, and never knew this to be a problem. I have always "tossed one down the tube" and then stuffed in a full mag.
I carry a Kahr CM40 everyday!
I also keep it topped off like that.
 
AFAIK, you have no choice but a 13/16 hex. And that sucks.

I have never seen that “J” series plug with anything other than a 13/16 hex.
I have the same problem with my Hedman 78030. #6 plug is hard to reach in the first place, and the tube interferes with a 13/16" socket. But I'll be fixing it soon... by putting on aluminum heads that use a 5/8" plug :D
 
QUOTE="Craig Burriss, post: 1973170706, member: 51401"]I carry a Kahr CM40 everyday!
I also keep it topped off like that.[/QUOTE]

LOL posted in the wrong thread. This post belonged here:

"Brutalizing the extractor"
 
906 heads with 2" TTI's. Done years ago. Contacted all the major plug manufacturers a couple years ago and as stated above, there is nothing truly compatible in 5/8" and the short 13/16"s are not correct either. No plans to make anything either as most guys are putting on aluminum heads which makes sense nowadays. Number 6 so hard to get too; a young 'wiry' tech friend was able to do get it done. He builds Subaru turbo engines and said the back plugs are so close to the firewall that he's had plenty of practice. Number 7 so close to the tube even a header socket didn't work. Had to use a crowfoot and was a pain. But not something that needs doing often enough to change the heads. Runs super clean and are probably good for the rest of my life. If I were doing an engine today then aluminum heads would be part of the build. Here's a pic of my modified crowfoot:

Crowfoot.jpg
 
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