It's been over 25 years since stroking a 350 small-block V-8 first became easy to do-hence, a very popular move-with impressive results. We're talking about the beloved torque-monster 383. We recently visited noted engine builder Joe Sherman at his facility in Santa Ana, California. Joe won the inaugural Popular Hot Rodding magazine Engine Masters Challenge seven years ago and has not looked back. When we asked him what a 383 had evolved into, he grinned and said, "As the 383 is to the 350, the 408 is to the 383."
He continued by telling us about his many hybrid 408 small-blocks, plus his latest one. The basic-form 408 Chevy small-block has been around since at least 2003-2004. But so have a lot of other non-stock Chevy small-blocks, including many factory crate engines. Why was Sherman touting his 408s, which he refers to as hybrids? Four reasons:
1. It is an internally-balanced engine. Some less powerful Sherman 408s (550 hp or less) have successfully been built and put into service using a factory 350 iron block. Hence, to the onlooker, the engine looks like a 350, as the block's casting number would so dictate.
2. Many of his USA and Western European customers have requested his 408 in different horsepower levels and have reported good results.
3. With a beefier aftermarket engine block (example: Dart) Sherman has created single four-barrel, solid, reliable engines, like the one in this story, producing in excess of 660 hp with over 560 lb-ft of torque.
4. Depending on the 408, the maximum horsepower is at 5,800 or 6,800 rpm, both very livable engine speeds.
408 CombinationsThe key to producing the maximum obtainable torque and horsepower in a given combination is to have the correct top-end combo: camshaft, heads and induction. Sherman's 667hp 408 has a roller camshaft which delivers over 0.700-inch valve lift with 1.6 ratio Jesel shaft-mounted roller rocker arms. It was ground with a 270/280 split duration and features mechanical roller lifters. It was also ground specifically for this engine. For your convenience, we have listed all component data in the technical sidebar. Yes, flat tappet cams can be created with the same lobe lift spec but roller cams create less friction and their lobe design lets the valve stay open longer-hence, more cylinder filling and power production.
To best work with the roller camshaft, Sherman's intake manifold of choice is an Edelbrock Super Victor. It was designed for maximum power production between 4,500 and 8,000 rpm. Sherman's carburetor of choice is a 1,095 cfm King Demon from Barry Grant. So here we have a 408ci small-block with 11.50:1 compression ratio pumping out 506 hp at only 4,800 rpm with 554 lb-ft of torque. The numbers increased to a maximum torque output of 562 lb-ft at 5,600 rpm and 667 hp at 6,800 rpm.
Sherman feels there is something special in Air Flow Research's newly designed 210 Eliminator heads. He thinks it could be the combustion chamber design and/or the water jacket cooling design- along with their large 210cc intake ports. The AFR stainless steel valves feature narrower 8mm stems with bead-lock retainers. This equates to a 10 gram weight reduction in valvetrain weight.
Both the crankshaft and rods are right out of Scat's catalog. The forged steel crankshaft has a 4.00-inch stroke. The I-beam connecting rods are super strong, generally lighter than others and have rod bolts that are clearanced to avoid contact with the cam lobes.
The pistons are also right out of a catalog, in this instance CP's. They are race-type pistons and feature short skirts, three-rings and flat tops with dual valve reliefs. With a 0.014-inch deck height, 65cc combustion chambers and a 0.030-inch thick/4.125-inch bore Cometic steel head gasket, the 667hp 408 engine's compression ratio is 11.50:1.