is it best to only mess with aluminum heads when cold?
same on intake... I've had the pleasure of pulling out some threads
on an aluminum intake one time when the engine was warm.
I felt the $$ floating away about the same time...
Not really because aluminum expands fars the stell when heated so the
hole size will grow quicker than the plug does.. If you have had
problems with threads coming out it is because either there were to
loose and leakge burned and gummed up thread so they strip or they
were over tightened when they were installed.
I love this one. you are kinding right? If it was going to "oval" it
would if plug was in there or not. Aluminum is stable and predicable,
it just has a different expantion rate the steel/cast iron.
On Fri, 07 Jul 2006 21:31:42 -0400, The Nolalu Barn Owl
That is because the aluminum block expands quicker and more than
insert which expands at same rate as plug. But if the helicoil is
sizeed propelry and inserted in head when it is hot so that it shrink
fits around helicoil, this will not happen. Blame this problem of the
individual installed the coil, not the head or its content. It is
still best to remove plug for a normal aluminum head will it is warm.
No I am not kidding. The chances of it actually happening are probably only
slight, but that is what they preach. The reason being that (as you have
already pointed out in previous posts) that aluminum expands at a different
rate than iron. An engine is assembled and torqued cold. As things heat up
the head has all kinds of push/pull stresses forced upon it. Which is fine,
the engineers have designed it to handle this. But when you take out one
simple spark plug, you have changed the structure.
Every engine head does distort a little when assembled so there is no
aurgument there but at what point is it a issue. THe hole may disort
by .001 inches or so from being true round but I would not cal it
oval shaped. Aluminum heads bolts to a cast iron block are usually
pretty reliable if properly torqued and not over heated as the bolck
helps keep them in shape so to speak.
If I may interject some information. I posted the original question
about aluminum heads and spark plug removal. The answer that SnoMan
gave to me was to remove the plugs with the engine COLD but if there
is any problem then WARM the engine up. There was no mention of
bringing the engine up to operating temperature.
SnoMan's answer was simple and concise and as far as I am concerned it
is also the most logical.
I thank everyone who showed an interest in the question.
All kinds of answers for a simple question. But a important step was only
touched on once. Once you get them out and are reinstalling be sure to use
antiseize on them. A good metal based antisieze, preferably nickle or second
best copper. Don't be afraid of it but be sure not to get any on the
electrode. Next time there will be no problems. Also just as a side note.
Use good quality platinum plugs, your choice. I prefer Bosch but OEM are
great also. Just pulled the plugs out of my wife's Pontiac Montana with 65K.
Measured gap and it was @ .062. .060 is factory setting. They were factory
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