a small amount of sealant can help, any excess will squeeze out when the cap is torqued before the stuff hardens. I have used a special sealant made by loctite? for sealing 2 machined surfaces that do not use a gasket. look at a machined surface like a main cap under a microscope
At the risk of sounding like a broken record. Please research what I have previously spoken of. Fretting. Also research "Ted Talks Astroturfing".
Now, on to my reply. I researched the official site for loctite and could find no reference to any type of product that they recommend using on the machine surfaces of engine caps before assembly. Do they have bearing retaining loctite? Yes, used for a totally different purpose. There is not one reference in any official publication on the use of any substance between the machined mating surfaces of engine main caps. Is there reference to coatings on bolt threads and different torque values for dry or coated bolts? Yes.
Anything that can allow a main cap to creep is a very bad thing. Silicone between the mating surfaces is a bad thing. If you look at the pictures he posted of his main cap mating surfaces, I'd want to know what the imperfection is to the far right of the picture. I'd be very worried that the surfaces aren't true, thus allowing all kinds of issues. Maybe the kind of issue he was experiencing. What about the uneven wear pattern in just the one main cap bearing. And have I looked at the machine surfaces under a microscope? Not sure were we are headed with that one. But I'll say NO just for factual reference. I'll also say that some machine surfaces have specified surface finishes. Think head gaskets, but that's another story.
Let me see if I can explain this a little easier. When your building an engine or anything for that matter. It's like traveling down the highway with guard rails on both sides. If there is a lot of tolerance in what your building, the guard rails are very far apart and your chance of crashing into them is very unlikely. No mater what kind of mess you make of things. Think farm equipment, mostly operated at low rpm, minimal wear, minimal heat. So you can have a lot of variances all over the road map and the thing will work all day long. Hell, olde Jon boy down olde creek road can fix that for you. I hear he has an awesome set of tools.
Now lets step up a bit. Your daily driver or in your case the street/track car. The guard rails are a bit closer together, and even closer when you run at the track at even higher rpms. Your tolerance must be held to a bit higher standard. Will snake oil tricks still work? You bet. But your chance for failure increases. Let me ask. When building a motor and doing your final plateau honing of the cylinders. Should you wipe them down clean with a paper towel soaked in a 50/50 mix of WD-40 and AFT fluid? Some say yes, some say no, some use a different magical blend. Is it wrong? Not if fits between the guard rails. Is it best practice? I don't know, how many box cars of paper towels did the big three order last year for there engine build shop.
I could carry this farther. Let take for example the space shuttle. Even with the best practices and hundreds of certifications and inspections. Things can fail. Why? Because the damn guard rails are so frecken close together, there is no room for "I read it on the internet, it must be true, it worked for me.
In closing. I will say. It is not the best practice to apply any coating between the machine mating surfaces of the main caps before assembly and final torque. They should be clean and true. Apply a touch to the seal ends, clock the seal ends? Sure if you want. Put some in the corner of the main cap after assembly? Sure why not. But assemble a motor with coatings where coatings don't belong.
LOOK OUT FOR THE GUARD RAILS!!!