Painting head gasket?????

[hjsmith00843]

About to put my motor togather and I was told to put a very light coast of hi temp paint on the sealing surface of the gasket.

Also on the 3 piece gasket I was also told to take out all but the top layer. This is to increase compression.

I was also just going to run HIGH Temp RTV on the cylinder jug between where it attaches to the block.

The specs on my engine are below. Would you do all of this?

[aDviSol2y]

How much would you gain from it? Are the risks going to outweigh the rewards? not sure.....

[F-16Guy]

I've heard of people coating one layer of a MLS (muti-layer steel) head gasket with high temp paint to aid in sealing with good results. It has to be either the top or bottom layer; the middle layer is just a shim to set deck height.

The purpose of using one layer of the head gasket and eliminating the base gasket doesn't really have as much to do with raising the compression ratio as it does with achieving the correct squish band clearance around the edge of the piston at TDC. With a piston that has the stock wrist pin height, the 400ex has a very large squish band. By thinning the head gasket and eliminating the base gasket, you are effectively raising the piston in the bore and thinning the gap between the edge of the piston and the corresponding area on the head at TDC.

What does this do? As the piston approaches TDC, the mixture of fuel and air that is lingering around the outside edges of the bore is squeezed into the center of the combustion chamber as that gap between the edge of the piston and the head closes. That concentrated mixture is now swirling around right in the middle of the top of the piston, and when the spark plug lights it, you get a more powerful, more efficient explosion of the mixture. The more efficient combustion transfers more energy to the piston and reduces combustion chamber temps, which means that you can run a slightly higher compression ratio on a given octane rating.

The head gasket is a good idea. The only reason I might advise against the base gasket being substituted with RTV is that there's an oil passage that goes from the case, up through the cylinder via the base gasket, and into the head to feed the cam. If you get RTV into that passage, you could starve the top end of oil and scatter the head. I have an FST-style secondary cooler that bypasses the cylinder passage, so it's not an issue for me, but if you don't have that, you're taking a risk.