Some M1 porting pictures and flow numbers

gzig5 said
Who did the additional port work to get the heads to 305cfm? I’ve got a set of ProMaxx 171’s that will need upgrading. I love this thread. I plan on a similar iterative process with an AirGap, M1, and TR5 tunnel ram. My M1 may be heading East for a makeover.

The “305 cfm” heads are big block heads Fishmen was talking about.

DNasty777 said
Does PBR have these heads on hand? I’d love to hear what he has to say about them. I know he said the trick-flows would be tricky (pun intended) to squeeze bigger valves in them because of the seats. Seeing as these two heads are very close in price, I’d love to know if he thinks he can get more out of the shockers.

@pittsburghracer

As he said….

The ProMaxx heads are chink castings bought to
Rainbow City, AL, and worked by the ProMaxx fellas. These were delivered to me with excellent craftsmanship. They stand behind their work. Since they are the chink heads, I’m sure there’s more in them. In speaking with ProMaxx on the phone about them, they were telling me there CNC program was what they thought was fitting for the head without pushing it to far while getting a great return in flow with the port shaping they came up with.

I would say that these heads at 185cc and the reported head flow would make these an excellent street head with great throttle response. They’re 10cc and 20 cfm down at max from the trick flow heads and I personally have a set of those on the wife’s 360 now. The ProMaxx heads will perform the same with low lift cams. It’s not until you start getting larger in duration and lift with the TF outshine the PM heads.

Look at there reported flow rates and compare.