Years before Chrysler put a flimsy aluminum intake manifold on the 225 and loaded the top end with a maze of superfluous vacuum hoses and wiring, the automaker attempted to make the slant six ...

We dyno test several intake manifolds plus a Dutra exhaust manifold on an aluminum-block Chrysler 225 Slant-Six and get 177 hp.

Slant Six guru Doug Dutra has a solution in his new cast iron Dutra Duals manifold set. They delivered 162.4 hp at 4,200 rpm and 215.1 lb-ft at 3,300 rpm, gains of 11.4 horsepower and 11.1 lb-ft.