Is Loctite Green 290 appropriate for use on the head studs on a 246GT (Iron) Block

No!!!!! Use a drop of oil only and re torque heads several times over a 72 hour period. Glue is not what keeps bolts and studs tight, stretch keeps them tight. Re torque is because studs stretch and lose their torque over time over a short time and this is one way to make sure of tightness w/out the need to remove head nuts and re torque after initial warming of a new engine. Because, you have to remove cams to access head nuts.
clay

 

Coolant keeps studs from rusting in the block, Use DVM to measure electrolysis in the coolant to check status of your coolant. These block head combination rarely show damage from electrolysis.

 

Yes, in the block, but up from that the exhaust side studs suffer from corrosion and caking.
Here are photos of myself and Bernd Buschen of European Autowerke disassembling the engine of Dino 05702. Note the last photo, where the exhaust studs are really grungey while the intake side are fairly clean. All are being replaced regardless of condition and only 2-3 on each side were difficult to remove.
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Either you or I misunderstood the question, that appeared to me to be about the end of the studs that go into the block (and often penetrate water jackets), not the nuts which go on the other end of the studs.

The equivalent of the ultimately-recommended Loctite 572 would be Permatex part number 59235, by the way. They both come in 50ml tubes for $11-$12 USD, also.

 

no damage, no loctite. damage, replace studs and maintain coolant w/a good antifreeze. When you remove studs you will find no corrosion on threads.

clay

 

wont new studs have initial stretch that long established ones have gone through?
why change them if they are not broke?

 

I think replacing them is a good insurance policy, specially if they have been known to strip the threads on torquing down.
If they break on a re-torque of the heads while in the car, well...you can see the inherent pain that otherwise could have been prevented beforehand, with the engine out.
I am also curious about what sort of product to use on the stud threads at the block, as you certainly would not want the stud to unthread itself if you loosen the head nuts to re-torque the head gaskets after a rebuild.

My guess, blue Loctite, as they are never coming back out, right?

Regards, Alberto

 

do you replace the because of old age or times disturbed, re-tourqued?
Or if in doubt change?

 

All the possible reasons you mention, lack of quality, unknown history, etc, etc, ....and that I like to sleep well at night....

Regards, Alberto