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Sun Aug 30, 2020 2:50 pm

See Solid threaded insert thread https://www.thesamba.com/vw/forum/viewtopic.php?p=8902559#8902559

Mon Aug 31, 2020 1:51 pm

It's almost impossible to thread any insert into a head and have it successfully seal combustion gases over the life of the head. However if the spark plug hole is not cracked it's always worth a try if you do your own mechanical work. The real problem is there is not a good sealant to use on the insert to head threads. There are cement sealants like "JB Weld Extreme Heat" 2400'F however it will probably develop a pressure leak after a few heat cycles. I have not confirmed this yet but worth a shot!
I have tried Permatex Red High temperature threadlocker 450'F and it bubbles out and leaks.

Worth a try when doing an insert would be Duda Energy PTFE Yellow Teflon Tape 3.5 mil thick, it's available on Amazon. I have used it for everything from the oil drain plug to sparkplug threads. Rated as high temperature as 698'F it's always held up on sparkplug threads for me. I would use 1 1/4-2 1/4 wraps on the Head to insert and make sure it's going in and not bunching up. It can also be used on the sparkplug threads at 2 1/4 turns for a spark that never will seize up. (A word of caution here though, Teflon tape is a good insulator so you will need an insert that is not so wide at the top that the metal on the plug only seals against the insert. The plug needs to make electrical contact to the head somewhere.)
Avoid inserts that are wrong for the spark plugs you use. The kind of inserts that require a hammer tap are wrong for Bosch and other Air Cooled VW plugs (I had one of these knock a considerable amount of the sparkplug hole boss loose into my combustion chamber. The engine spit it out ok though. The head had to be removed from the engine for a welded repair but still leaks to this day unless I use the teflon PTFE tape to seal the sparkplug threads. )

If I ever get into a situation where a insert is needed on a sparkplug again I would probably use the ACN Time Sert and install it with the head removed from the engine maybe try the Teflon Yellow PTFE tape. I think it has the best chance of sealing however, I would also use it on the plug side too from then on, so the plug unscrews easier than normal and maybe reduce the tightening torque on the plug to 18 foot/lbs If the engine was running good on a given plug I would not change it at the normal 6000 miles. Why risk the insert coming out?. (It's best to Never change plugs on a hot or even a warm engine due to the heat expansion of the spark plug.)
Sign of a leaking spark plug seal:

JB Weld 2400'F Seal:

Wrong insert Wrong method to install Wrong sealer:

White Teflon Tape 3 1/4 Turns will also work:

This Weld Repair stripped out:

This second try held but leaks a little and I think it may strip out soon:

Mon Aug 31, 2020 2:31 pm

Cusser wrote: See Solid threaded insert thread https://www.thesamba.com/vw/forum/viewtopic.php?p=8902559#8902559

This has worked fine for me.

Engine has not been apart since I assembled it in 1986, so this repair has been very successful.

Mon Aug 31, 2020 5:06 pm

1986 spark plugs? :D

Cusser wrote: Cusser wrote: See Solid threaded insert thread https://www.thesamba.com/vw/forum/viewtopic.php?p=8902559#8902559

This has worked fine for me.

Engine has not been apart since I assembled it in 1986, so this repair has been very successful.

Tue Sep 01, 2020 2:45 pm

Check out this 36 Horse head, Not sure if they all had inserts or what, Looks Factory:

Tue Sep 01, 2020 5:44 pm

nope, not factory, maybe VW rebuilt insert or a specific brand. I have several in my small parts drawer.

Tue Sep 01, 2020 7:51 pm

[email protected] wrote: 1986 spark plugs? :D

Cusser wrote: Cusser wrote: See Solid threaded insert thread https://www.thesamba.com/vw/forum/viewtopic.php?p=8902559#8902559

This has worked fine for me.

Engine has not been apart since I assembled it in 1986, so this repair has been very successful.

John - you know better than that, quit funnin' me !!!

Obviously, replacing spark plugs, changing oil, etc. is NOT taking an engine apart !

Sat Aug 03, 2024 6:48 am

When putting the heli coil on the plug should I remove the washer that comes on the plug? I have 1/2” coil and it seems a touch too long with that washer