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On 28 Dec 2001, at 17:40, Herman Haustein wrote: > I'd recommend, if you pull the head, not to go with the helicoil as > this is at best a temporary fix. Rather have a machine shop do inserts > - if you can have both heads done go to 3/4" thread. The 3/4" dimension is the LENGTH of the thread and there just isn't that much metal there. The SP hole is crammed right in between the 2 valve seat inserts, so increasing the diameter to 3/4" (even if there was such a size) would weaken the head too much (it's already weak there.) I really dislike the solid inserts as they tend to come out every time you change plugs, so they aren't nearly as good a fix. They also have a shoulder on the outside which the plug seats against. This is in the primary cooling path for the heat flow out of the plug. Changing the thermal resistance along this path effectively alters the heat range of that single plug. The Heli-coil inserts wedge themselves in there and won't come out unless terribly abused. The amount of abuse that this takes is MUCH more than a normal, unrepaired, SP hole should be subjected to. All this assumes that the Heli-coil is properly installed. It should be recessed 1/2 turn below the outside surface, with no extra material projecting into the combustion chamber. I have one engine (about to be replaced) with a solid insert. It is an annoyance EVERY time I have to pull that plug. I have a couple of engines with Heli-coils in them. I know they are there because I installed them, but I've forgotten exactly WHERE they are because they never call attention to themselves. Sorry, but I just really don't like the solid inserts. Many mechanics do, but I believe it is just because they are easy to put in. That gets the car out of the shop, but it starts a chain reaction of annoying incidents for years to follow. - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- Unsubscribe? mailto:type3-request@vwtype3.org, Subject: unsubscribe