Cam, Heads & Induction

Looking to run in the Street Division of competition in the 2012 AMSOIL Engine Masters Challenge, a hydraulic roller cam was required equipment. Henderson wanted to run aggressive lobe profiles and had a custom camshaft ground using solid roller lobes from COMP Cams. Henderson arrived at the specification of 246/251 degrees duration at .050-inch lift; "I had more duration in the cam than many of the other engines in the competition because I was working with an inline-valve 23-degree head. The cross-sectional area is limited at the pushrods, and the flow is less than you might get from a canted-valve or Hemi engine. The cam puts the power where it needs to be in the rpm range." To work with the cam, Henderson used a set of COMP's limited-travel retrofit hydraulic roller lifters. As Henderson points out, "With a hydraulic roller at this rpm range you do not have to worry too much about lifter pump-up, but there is .160 inch of travel for the lifters to collapse, especially with high spring loads. The limited-travel lifters eliminate that possibility. I set them up at about .006-inch preload, which is very close to zero lash when up to temperature."

Topping the engine is a set of AFR Eliminator 235 cylinder heads. These heads feature the common 60/40 shift, where the intake and exhaust valve are relocated to increase the clearance for larger valves. Henderson tells us, "With this head, an offset rocker provides increased valvetrain clearance, but I was using a standard set of COMP Hi-Tech Stainless rockers in a 1.7:1 ratio. The relatively high ratio delivers .725/.734-inch lift, but the clearance to the intake port was limited with this head and rocker combination. I ended up having to grind for pushrod clearance and also had to use 5/16-inch pushrods. Bigger pushrods would have been better, but I made the 5/16-inch pushrods stiffer by going with a wall thickness of .015 inch."

Henderson says the AFR cylinder heads are the best you can get in a conventional 23-degree Chevy small-block head. Henderson ordered the heads with AFR's competition level CNC porting with little further modification: "With these heads you will have a hard time improving the work done by AFR. I know that they invest significant R&D in developing their ports. All I did was a port-match and add the springs and titanium retainers." Henderson went with a COMP Cams dual valvespring assembly delivering 140/500 pounds closed/open load, and found the arrangement worked very well in the operating rpm range of the engine. Henderson disclosed: "I didn't go crazy with the spring loads, but the engine pulled cleanly at high rpm with no sign of valve float or instability."

Feeding the cylinder heads is an Edelbrock Victor single-plane intake manifold converted to fuel injection by the late Jeff Kobylski of Modern Cylinder heads. Henderson details, "The Victor manifold had the cloverleaf Dominator intake flange I wanted, and the runners have a nice taper to them. Modification to the intake was just a basic cleanup and blending, and adding the bungs for the injectors." Working in conjunction with the Victor manifold is a DFI electronic fuel injection system from ACCEL. The Dominator-flanged four-barrel throttle body from ACCEL is nothing short of giant, with an airflow rating of 2,100 cfm. This unit meters the air, while fuel is supplied by ACCEL 55-lb/hr injectors and ACCEL rails, and control is provided by an ACCEL ECU and software. The EFI system incorporates a complete ACCEL ignition system to handle the spark timing requirements.

Henderson spoke enthusiastically about the ACCEL system: "This was my first experience with fuel injection, and the support I got from ACCEL was outstanding. The EFI system allowed very precise control of the fuel and spark, and that helped optimize the power possible from this engine combination. After my experience with ACCEL, I would not run any other fuel injection system."