Why is a lower displacement motor better for boost? Always have wondered why.
Thicker walls i believe.
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The cylinder wall thickness is the same, the change in displacement is due to a change in stroke.
We always push the 392 over the 426 for high boost/nitrous applications for 2 major reasons.
Compression Height and Crankshaft Overlap
Compression Height: When Compression Height gets as small as 1 inch, it often requires narrow piston rings. It may also require the rings to be closer to the top of the piston than you may want for nitrous or endurance use. Short piston height means lighter weight, which is good, but it may also give up reliability you need. Sometimes a compromise for less stroke or shorter rods is prudent.
426 Compression Height: 1.085"
413 Compression Height: 1.115"
393 Compression Height: 1.218"
The increased compression height allows us to utilize a thicker crown for extreme boost/n2o applications. You will slowly see us transitioning from 393 builds towards 413's for our higher hp applications. As soon as I get my car back, we will be building a 413 for it. The 393 is still going to be a stronger option, but the 413 will allow us to make the same amount of hp as a 393 with less boost due to the additional 20 cubes.
Crankshaft Overlap: Crankshaft overlap is simply how much of a crank's main and rod journal diameters overlap each other. As stroke is increased, moving the rod journals farther away from the main journals reduces overlap and compromises strength and durability.
426 Overlap: .255"
413 Overlap: .330"
393 Overlap: .430"
