I was considering ways to reduce engine noise and had a thought.... 

What about filling the low areas in the "corrugated" engine compartment cover with "silicone seal"  or some similar caulking compound.    Not just the hatch-cover, but the whole top surface and forward-slanting front surface of the engine / transmission enclosure.  

My concept is that this would be similar to the factory-supplied foam pad that is under the rug in the central area of the van that similarly levels-out the corrugation in that section of the floor.

Any thoughts or other suggestions would be appreciated.

Fin Beven
'84 Vanagon GL, camper-conversion
'90 Vanagon Carat, camper-to-be