The history of exotic cylinder head conversions for production engines is distinguished with legendary names like Westlake, Ardun, McGee, Lyons, Riley and Moser. Even Mickey Thompson developed a 3-valve head for the small-block Chevy. You can also add Chet Herbert to such a notable list.
“This is a one-off billet aluminum cylinder head that Chet built for the small-block Ford while he was alive,” says Bob Vrbancic of Vrbancic Brothers Racing and the Carb Shop, the teams behind the engine in the video. “We had dealt with Chet for a long time when he was based on the West Coast. He started making the heads and asked us if we would do some R&D for him.”
Initial development work started around eight years ago on a Ford FE application.
“We have a big-block Ford with those heads that we run in a Top Sportsman car,” says Vrbancic. “It makes about 1,440 horsepower with a Roush block.”
This small-block version is based on a Dart Iron Eagle 9.5-inch-deck block bored out to 4.165 inches and fitted with a Lunati 4-inch crankshaft (436ci) and Diamond pistons (9.8:1CR). The cylinder heads have limited coolant flow and feature custom rocker arms.
“There’s actually a very small combustion chamber at 46cc. It is a true hemi but basically, it’s all valve,” says Vrbancic, noting the valve sizes at 2.400 intake and 1.900 exhaust. “There is water going through the head but it’s not a conventional water jacket. It does keep them cool, though.”
Herbert also designed a custom 3-piece billet intake manifold in which the center section is actually part of the intake port, according to Vbrancic. Sitting on top is a pair of Carb Shop-prepped Holley HP carbs. Rounding the engine assembly are a Jesel belt drive, Meziere water pump and MSD distributor.
With a “small solid roller” the engine makes just over 800 horsepower at 6,600 rpm on pump gas. Peak torque was 671 lb-ft at 5,200 rpm. Final destination is a street rod.
“The customer wanted something no one else has,” says Vrbrancic.