That was me who posted about the 5 CFM . Had a friend port my heads and he went to the Mondello school . Did some BBC and the 6.5 heads for me . I have never seen any numbers from Chris on his ported heads . If you are in the business of selling 6.5 heads , why wouldn't you post some numbers ...
This have the 2 master cylinder brake system ? One on the firewall and another under the truck mounted to the frame under the seat ? I would almost try taking off the master cylinder and starting the truck to see if the seals are blown . Are the pressure return lines on correctly ?
Good , that's what I'd do with my ported heads . I would do a " line of sight " with the runners . That looks like a lot of taper on the runners and very short for the intended RPMs . You'd be doing great if that causes the heads to only lose 5 CFM .
Try checking voltage at the starter while cranking . I have a 91 Suburban 350 that eventually stopped cranking . Voltage was good at the battery end and on the starter but went to nothing when cranking . Replaced the cable , had battery voltage while cranking and started .
There were issues with the trans harness at the connection on the side of the trans . If you pull the connector and find trans fluid in the cavity , there are updated parts to repair that . This was on the earlier trucks , I have a 91 Suburban , and the ends were different on the newer parts .
Rock Auto is showing two different part numbers for the 96 and 97 3500 . I would think you would need to know the brake system numbers for ordering the correct parts i.e. JB7 or JD8 etc . These are on the glovebox door with all the other codes .
I remember reading those pages on the theory about precups when you posted them a while ago . First sentence is a red flag for me . Only 40% of the swept volume is in the prechamber ? Where is the other 60% ? Remember this is at TDC . Not happening as you have stated because of the pressure...