Let head bolt sealer "skim off"?
When using a sealer like Permatex #2 or an RTV is it recommended to apply the sealer to the male and female threads and then allow it to set up or skim off...as you would when using the product as a gasket or gasket sealer?
I've always just applied it and then inserted and torqued down the bolts. But in a number of threads folks have noted that the sealer, when used with gaskets, should be allowed to set up and form a skin before mating the surfaces. So I'm wondering if the same holds true for sealing head bolts. Or would allowing the sealer to set up be potentially detrimental when using it on bolts and having the threads cut and possibly dislodge the sealant? Might it also effect torque readings if allowed to set up or skim off first, especially when applied under the head of the bold to reduce friction during the torque down process?
I only let the sealer "skim over" for about ten minutes or so when using it on the ends of the block for the intake manifold.
I also use it to "glue" the cork gaskets to the valve covers.I don't use any sealant on the cork valve cover gaskets to the heads.
When using on head bolts, I just apply it to the threads only and install with no "skim over" time. I put a few drops of oil under the heads of the bolts. Then torque from the center out in three step increments. This works for me.
FWIW, I've not found it to be necessary to put anything on the female threads- just on the bolt threads. I use Permatex #2, myself. It's not as slippery as RTV or most thread sealers, so I add a couple ft/lb to compensate.
If I were to use RTV, I agree- no skin time. BTW, it is fine to use. It doesn't set up immediately in the absence of air, so will still be pliable when a retorque is done. After an extended period of time and heat cycling, it does eventually set up, and this is born out when disassembling engines that have had RTV used on the head bolt threads. Permatex #2 doesn't harden, but is much more viscous than RTV.
As for lubing the bolt head/head surface interface, I use a smudge of moly lube around the head's bolt hole surfaces. This is just a matter of convenience, it makes little difference whether the bolt or the head's surface gets lube- as long as one or the other gets it. RTV will be a poor lubricant in this instance (between the bolt and the head)- way too much pressure for it to truly act as a lubricant, IMO. But better than nothing.
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