Cylinder Heads
Currently, Indy offers two different basic AMC heads: the Street-Replacement 401-SR head and the full-race 401-1 with huge valves and raised intake and exhaust ports. For this street-driven engine, Brandes chose to go with the milder 401-SR design to enhance midrange torque output. Unlike the full-race version, the SR's intake-port entrance, exhaust-port exit and valve spacing mirror the original AMC design, simplifying installation in a street car. However, the SR head's 2.10 intake/1.650 exhaust valves are longer than stock, making them more compatible with stout aftermarket valvesprings.
As delivered from Indy with a mild bowl-port and intake gasket-match, the SR casting considerably outflows the AMC stock heads over 0.400-inch lift -- even the '70-and-later design with its improved dog-leg exhaust ports. Brandes turned the heads over to his main "tumble-and-swirl" man, Ron Sharp at Advanced Airflow. Sharp is mum about the exact details, but he does reveal that the as-delivered Indy three-angle valve job was upped to a five-angle on the intake to help atomize incoming fuel. The exhaust-side valve job is completely radiused with no discreet angles off the seat.
Sharp also reworked the intake-side short-turn radius, then opened up the cross-sectional area around the pushrods. He touched up the chamber and reworked the exhaust-port roof. All this results in significant flow improvements across the entire lift range.
Intake:
Stock AMC | 
Indy 401-SR
The intake floor on the Indy 401-SR head is smoothly radiused in its approach to the valve bowl. It has generous 235cc intake runners -- 69 cc's larger than typical high-perf AMC heads. | 
Exhaust:
Stock AMC |
Indy 401-SR
The exhaust side has the most "sweeping" changes. Note the Indy 401-SR head's smooth and consistent cross section. As-delivered volume on the enlarged port is 105 cc's, yet it still exits in the stock location. | 
When this engine was built, Indy heads were the only aftermarket AMC castings available--but for 2004 there'll also be Edelbrock AMC heads with 2.02 intake/1.60 exhaust valves, 58cc combustion chambers and adjustable stud-mounted rocker arms. Intake and exhaust ports remain in the stock AMC location. | 
The Indy head's thicker outer flange area can cause interference with some header sets, which may need to be ground for clearance. The engine was dyno'd with a set of ceramic-coated Hooker headers (PN 7104-1HKR, 1 5/8-inch primaries x 3-inch collectors). |
Camshaft and Valvetrain
One of AMC's advantages is its large 0.904-inch-od lifter foot, the same as a Chrysler. Most GM and Ford stock flat-tappet lifters measure only 0.842 and 0.875 inch, respectively. The larger lifter diameter results in a greater foot-to-cam-lobe contact area with reduced unit loading. This allows grinding really aggressive flat-tappet lobe profiles that approach roller-cam performance without the expense of a billet roller.
Brandes worked with Comp Cams to come up with a custom, "real AMC" mechanical flat-tappet grind that takes advantage of the big foot, matches the flow characteristics of the Indy cylinder heads and complements the engine's high static compression ratio.
Camshaft Specs
Manufacturer: Comp Cams
Part No.: 10-000-5 (custom)
Grind No.: A8 6585/7118 S 108.0
Type: Mechanical flat-tappet
Valve Lift (1.6:1 rockers): 0.621/0.624 inch
Duration (at 0.050): 255/262 degrees
Intake Opens/Closes (at 0.050): 19 degrees BTDC/55 degrees ABDC
Exhaust Opens/Closes (at 0.050): 59 degrees BBDC/23 degrees ATDC
Intake Centerline: 108 degrees
LDA: 108 degrees
Valve Lash (Hot): 0.018/0.020 inch