Thread inserts in the Norton head

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Jim Comstock wrote: "Regular helicoil inserts -not the solid ones- work fine for spark plugs. Just install them 2 or 3 threads deep to keep them from coming out."

This caught my eye because I know a couple of friends who had a problem with the helicoils unscrewing with the spark plug. I am not sure what it means to install them 2 or 3 threads deep, or why this would keep them from coming out with the spark plug?

Stephen Hill
 

comnoz

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Jim Comstock wrote: "Regular helicoil inserts -not the solid ones- work fine for spark plugs. Just install them 2 or 3 threads deep to keep them from coming out."

This caught my eye because I know a couple of friends who had a problem with the helicoils unscrewing with the spark plug. I am not sure what it means to install them 2 or 3 threads deep, or why this would keep them from coming out with the spark plug?

Stephen Hill
Screw the helicoil in a couple turns after it is flush with the plug seat.
Because the sharp end of the coil will usually dig in a bit so it doesn't come out with the plug.
To help I used to take a punch and mash the thread a little just above the helicoil and use a spot of antiseize on the plug.

Are they perfect, no, but at least they don't crack the head like the solid plug inserts often do.
[And that's why I started doing the stepped Al/bronze inserts.]
 

comnoz

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And to make it more embarrassing, I couldn't find a 5/8" length 3/8-16 helical wire insert from any other manufacturer (Recoil, Precision, E-zlock, etc.). It seems like they all mostly pick lengths as a multiple of the thread nominal diameter, i.e. 1.0x, 1.5x, 2.0x.

Ken
I just buy them all long. Then wire snippers will make them any length I need.
P1030054.JPG
 
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The helicoil may measure 9/16" overall but it only measures 1/2" down to the tang. Removing the tang requires a deeper hole and its a messy job that doesn't always go smoothly (the tang can bend instead of breaking or jam into the bottom of the hole). Removing the tang gives you about .540" length but most people probably just leave the tang alone.




Starting with a longer helicoil and cutting it to length isn't a good solution because you still have to cut it close to 1/2". That's because the helicoil kit comes with a plug tap and you have to drill a deeper hole than the helicoil to tap it deep enough and leave extra depth to be able punch downward to remove the tang. The photo below shows a helicoil plug tap compared to a bottoming timesert tap for a 5/8" long timesert. A helicoil bottoming tap would help but you still have to provide the extra depth for the tang and/or its removal.


The studs in a Norton head are in blind holes and that limits your drilling depth. I still think the best option is to use the longer 5/8" timeserts instead of the shorter helicoil. Plus a timesert looks better, won't retract like a helicoil can and you don't have to fuss with removing a tang.

Vids like the "Thread insert deathmatch" do not really apply to a Norton head because you can use a longer timesert (than a helicoil) in a Norton head.

Here's a vid showing how the install the 5/8" deep timeserts in a Norton head.
 
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