After decades of convincing people to spend the money on aftermarket aluminum heads, the first question people ask is why? Some assume it might be cheaper, but unfortunately that is not the case. Honestly, well ported Performer RPM heads will flow as much air, weight less, and features a closed chamber for quench. Since they are made out of aluminum repairs are easy if anything ever does go wrong.

Then next question is the same as the first, why? “906” iron heads are hard and difficult to port. They also are now at least 40 years old and need valve guide work, new valves, and hardened exhaust seat for unleaded compatibility, BUT if you have a 68-70 ½ Chrysler product, these are the correct heads for your mopar big block. Since the 68-70 ½ years might be considered the “premium” years for mopars of value, there are a large amount of people who want to improve engine output, but still maintain the OEM appearance. These CNC’ed 906 heads are not only for hot street cars but for a number of OEM appearing class racing organizations like FAST (factory appearing stock tire).

To meet the demand of this niche’ market we now offer CNC porting for 906 heads. I have been asked many times about programs for other castings such as 452 heads. The problem is that because iron is much harder than aluminum, it takes more machine time to port the heads. The iron heads are also harder on tooling. Because of these reasons, CNC porting iron is more expensive than aluminum. Honestly, In a performance application other than OEM appearing, you are better off upgrading to an aftermarket aluminum head for a hot street or bracket racing application. Our CNC ported 906 heads are specifically designed for class racing and people with certain year cars that want to maintain OEM appearance.

EVERYONE is obsessed with flow numbers. While they are important they are not everything to making power. To sooth the information junkies that exist out there, here are the flow numbers.

	INT	EX
.200	153.5	128.4
.300	222.3	165.2
.400	267.9	200.1
.500	303.8	215.4
.600	313.1	223.5
.700	309.4	223.5

Head flowed w/2.14-1.81 valves, 45 degree VJ, 2.375 bore, no ex tube.

As you can see the ex easily flows over 70% of the intake and with 313 cfm you can easily support well over 650 HP.

For Muscle Motors to supply complete heads that feature: CNC porting with polished chambers, Stainless valves, new bronze guide liners honed to size, hardened exhaust seats, surface milled, any hydraulic or solid cam springs, 10 degree locks and retainers, new seals and are fully assembled, $2299 outright, no core charge. If you send your core heads deduct $200.

Mike @MM