All it took was a call from a long-time Mopar friend, Vic Palumbo. "Hey Dan, I bought a set of Indy SR [Stock Replacement] heads. Could you port and bolt 'em on my '67 GTX?" My reply: "Sure Vic-providing we could use your car for testing. The Indy SRs would have to prove themselves against a set of 906 heads with the typical modifications." Vic didn't realize the change would require new headers and an installation kit from Indy Cylinder Heads, which includes longer pushrods, an external oil line kit, and head bolts. One thing not included was the valley cover plate that would be necessary to perform the head swap. We ordered a set of TTI headers, specific for the Indy heads, along with a complete TTI exhaust system. Also ordered was the aforementioned install kit and valley cover from Indy. Vic's '67 already had sufficient hood clearance with a Hemi hoodscoop, and at this point we felt we were good to go on with the swap.

Before ponying up the jack for a set of Indy heads for your big-block, consider this: Your B/RB will need at least a 10:1 compression ratio, a high-lift, high-velocity cam (preferably a solid roller), a high-stall converter (matched to the cam, heads, and gearing), and steep gearing of 3.91s or better. The 440 in the GTX is a 10.5:1 Ray Barton Racing Engines (RBRE) short-block with a Comp Cams hydraulic cam with .501 inch lift, and a duration of 244 degrees at .050. The 906 heads came from a local machine shop with the larger 2.14/1.81 valves, light bowl work, and gasket matching. On the flow bench the iron heads were good for 241 cfm at .500 inch lift (flow stalled above .500 inch lift). Stock 906 heads with the 2.08/1.74 valves will usually flow 210-220 cfm at .500 inch lift.

Max Port
Our original intentions were to fully port and polish the Indy SRs, back-cut the intake valves, and retain the stock 906-size intake port openings. We brought the aluminum castings-one ported and one stock-to the RBRE facility in nearby eastern Pennsylvania. Mike Barton flowed the SRs (Mike has flowed and ported many Indy heads), and back-cut the intake valves to 28 degrees. Satisfied with the flow numbers, we called Russ Flagle at Indy Cylinder Head (ICH) about our results. Russ highly recommended we enlarge the port openings to the Max Wedge size. Max Wedge ports are typically 1/2 inch taller than a stock 906 port. We also removed .150 inch from the pushrod pinch area and blended that area as well. The Max Wedge-size port openings raised the flow numbers at low, mid, and high lift through the roof (see charts). Indy sells the SRs already CNC-ported with the Max Wedge-size intakes. This will save you many hours of porting.

We wanted to reuse the Edelbrock Performer RPM intake, and gasket match it to the Max size. The problem is, there's not enough material to do so. This prompted us to use the Indy 440-2D RB dual-plane intake. This intake features taller runners and larger ports, but is similar in design to the Performer RPM, which utilizes stock 906-size port exits. Fortunately, the Indy intake had plenty of material for us to port match to the Max Wedge size. This street/strip intake delivers a high, broad torque range with excellent throttle response-great for street-driven cars. The same 850 Speed Demon carburetor was employed for all strip and dyno duties.

Install And Combo
So far, the head swap required the Indy intake installation kit and TTI headers, because the Indy exhaust ports are 3/4 inch higher and 1/2 inch wider than stock ports. Earlier we mentioned a high-velocity cam would be advantageous in promoting air velocity with Indy's larger intake ports. So we tossed the stock 1.5-ratio rockers in favor of Indy's 1.6-ratio roller-tip rockers. We also enlisted a pair of Indy's thick-wall rocker shafts. The SRs can use any stock-type replacement adjustable rocker, and there is no need for expensive offset rockers. The 1.6 rockers will help the .501-inch-lift Comp cam to act like it has .530 inch valve lift while speeding up the valve and airflow.