This is a topic which gets aired fairly frequently.
18 or 20lb.ft should be perfectly OK, better still if you tighten in small increments following the recommended sequence.
Personally I never use any sealant, just a smear of grease.
The nuts should be torqued up again after initial running.
Always tighten with the engine stone cold.
Otherwise the main thing to consider is whether your head and block upper face are truly flat. Cylinder heads are often slightly concave in the middle. I prefer the old-fashioned remedy of lapping out any hollows on a surface plate (milling or grinding takes off too much metal and hikes the compression ratio).
If these surfaces are not flat within a thou or two the gasket will struggle to seal.
18 or 20lb.ft should be perfectly OK, better still if you tighten in small increments following the recommended sequence.
Personally I never use any sealant, just a smear of grease.
The nuts should be torqued up again after initial running.
Always tighten with the engine stone cold.
Otherwise the main thing to consider is whether your head and block upper face are truly flat. Cylinder heads are often slightly concave in the middle. I prefer the old-fashioned remedy of lapping out any hollows on a surface plate (milling or grinding takes off too much metal and hikes the compression ratio).
If these surfaces are not flat within a thou or two the gasket will struggle to seal.