When Chris Henderson of Henderson Machine looked to build a top-level street engine, he lo
When it comes to building power on a budget, the surefire formula for success is to start with the biggest factory engine you can find and use that framework to its maximum potential. In the world of Chevrolet small-blocks, that framework is the factory 400 block. The capacity for power is already built into the 400, with a bore size that dwarfs the other factory small-blocks at 4.125 inches, standard, and a factory stroke of 3.75 inches. When looking to make Chevy power on a budget, the appeal here is that you really do not have to make radical alterations to the factory combination in search of cubes; you can spend your time and money optimizing those cubes for serious horsepower.
That was just the plan Chris Henderson had in building a small-block Chevrolet for the AMSOIL Engine Masters Challenge. The idea wasn't to reinvent the small-block. Rather, Henderson makes the most of the best of what's already there. Henderson's philosophy is to pay attention to the details, and letting all of those small improvements add incrementally to a good basic package.
If you are going to build serious horsepower, you'd better pack some beef into the block.
This engine was based upon a production 400 block, but Chris was looking to improve on the factory's original layout. First thing on the hit list were the short OEM rods. One of the drawbacks of the original 400 Chevy was the short 5.565-inch connecting rod, which increased cylinder wall loading and led to accelerated bore wear when the engines were delivered as OEM. While a common upgrade when building the 400 is to use 5.7-inch connecting rods, Henderson is a believer in the long-rod advantage, leading him to employ a 6.00-inch rod combination. Henderson explains his thinking: "I selected a 6-inch rod so that there will be a longer piston dwell around TDC. This will require a small enough port to keep an accelerated air velocity for good cylinder filling, but with a large enough port to make enough higher-rpm power."
While it seems like this situation would create a difficult balancing act, the port size was largely determined by the intake manifold of choice, Edelbrock's Performer RPM Air-Gap. Henderson tells us, "My rod-to-stroke combo has a 1.6:1 ratio, which responds better to larger port volumes, with larger cfm carbs relative to the displacement. My ports are as big as I can practically make them with the intake."
Starting with the production block, Henderson began with modifications to ensure the block's integrity at the expected high power level. The block was prepped with a partial fill using Moroso block filler in the water jacket, a move that increases the cylinder rigidity and also helps with piston ring seal. Eagle billet four-bolt main caps clamped with ARP studs add even more
security to the lower structure. Prepped like this, the factory block can be very reliable at high power levels.
The crankcase was relieved for reduced windage and improved drain back. The grinding and p
You will not find the factory crankshaft residing within the reinforced block structure, but rather a Scat Aero-wing crankshaft in the factory stroke. The crank is made with 350-sized main journals rather than the larger 400 mains, with COMP bearing spacers taking up the slack. This move reduces bearing speed and drag, and Henderson is always looking for ways to reduce parasitic drag in the engine assembly. Henderson favors this crankshaft for windage reduction, a theme he carried through to his block prep by relieving and polishing the inside of the crankcase for increased clearance to the crank as well as improved drain back.
To further reduce the possibility of unnecessary windage-related power losses, the lifter valley was fitted with standpipes, and the oil drain directed to the front and back of the engine. Henderson says, "Up front with the Jesel beltdrive, there isn't anything for the oil to get caught up in; it's all smooth up there." Completing the rotating assembly, Henderson filled the bores with off-the-shelf Mahle domed pistons with a compression height of 1.125 inches, giving a compression ratio of 11.4:1.
Taking the windage reduction further while substantially increasing the strength compared
A large part of Henderson's build strategy centered upon the conversion to long 6.00-inch
Note the short 1.125-inch compression height of the piston when the longer connecting rod
Up at the lifter valley, the astute observer will note that the return of oil from the top
The cylinder heads and the associated valvetrain components are a key to performance and r
Looking down the intake ports, the handwork done to the passages is evident. The final int
A stiff valvetrain with minimal flex helps reduce the possibility of valvetrain deflection
In keeping with the idea of creating a stiff valvetrain while looking to achieve this goal
A Jesel beltdrive system turns a COMP dual-pattern custom cam, ground with 246/258 degrees