Copper coat works fine, just make sure it is a thin coating. Add this to your
list of prep things if you don't do it already;
1)bottom tap the bolt holes - in case you don't know, a bottom tap cuts thread
all the way to its very end, it has no taper at the end to help start the tap.
This means you can't use it to make threads in an untapped hole, but it works
fine in a hole that already has threads and will add threads to the bottom of
the hole where the regular tap originally used didn't cut any threads
2)countersink the bolt holes - I have a big multi-fluted 45 degree countersink
that I use - give it a generous countersink, about 1/4" deep. This will create a
"pocket" at the top of the hole which will give any material that is pulled up
around the bolt a place to go without it affecting the flatness of the top of
the block and without affecting the sealing of the gasket.
By countersinking you will lose a few threads near the top but that will be
offset by the bottom taping and combined this will actually move the clamping
zone even further down in the block, which means a better hold and less
distortion of the block. In fact I use this procedure on *every* bolt and stud
hole on an engine. The countersink may create a small raised ridge around the
hole, so I do all this before I have the head and block surfaced, but if you
have already surfaced the parts, you can remove the ridge with a fine
scotchbrite wheel on a die grinder if you are careful.
Last thing, be careful with torque values on oiled or lubricated fasteners. As
far as I know, torque values are always given for dry fasteners. You have to
reduce the torque considerably if you lubricate the threads. If I recall
correctly, ARP says to reduce torque by 45% for oiled fasteners, maybe someone
on the list has better figures on this. This won't decrease the clamping force
the fastener applies to the parts because you will have turned the fastener the
same amount as you would have with dry threads and the original torque figures.
Torque figures are calculated to provide a certain clamping force based on the
torque required to turn the fastener. The fastener's resistance to being turned,
due to friction between the mating threads, is part of this calculation. They
use dry threads to make the calculation and if you oil the threads there is less
friction and therefore less resistance and you will actually over tighten the
fastener if you use the original torque figures.
datsunmike wrote:
>
> Chris,
>
> Make sure the head is true and check the block too. Clean all gasket
> surfaces thoroughly, I use fine scotch brite wheels mounted in a drill then
> lacquer thinner. Chase the head bolt threads on the block to get the crap
> out and so you get a good pull with not too much friction from dirt and
> crud. I use oil on the bolts. Clean the crud out from the cylinder bores and
> elsewhere. As Fred Katz said, use paper towels as they are not as
> destructive as cloth.
>
> I am using Cooper Coat on the headgasket unless someone has had bad
> experiences with it. Please send your comments.
>
> Mike
>
> ----- Original Message -----
> From: <Christhman@aol.com>
> To: <datsun-roadsters@autox.team.net>
> Sent: Sunday, May 27, 2001 3:49 AM
> Subject: cylinder head removal
>
> > anything in particular i should look out for? and is putting never sieze
> on
> > the head bolts recommended? thanks, damn head gasket blew (previous
> > owner).......Chris
--
Marc Sayer
82 280ZXT
71 510 2.5 Trans Am vintage racer
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