K4fxd MMR and other brands are designed off removing the factory freeze plugs, and install a crossover line between the heads for coolant flow, all they did is copy what was done from the 4.6L motors that Ford made from the factory. That's what Jackson1320 posted a pic of.
Used Bama tune for a few years. Had issues at steady throttle in the 1800-2100 RPM range. Had an PMAS intake and Boss manifold with 47LU injectors, and headers. Changed to 18 mani still same throttle issue. Swapped to boosted setup and Palm Beach Dyno tune and no issues since. Bama was ok for...
I installed the upr version of this, when the motor was out. Haven't noticed a difference. When my first motor blew it took out cylinder 6, not quite 7 or 8.
When the crank timing gear was on the end of the crank the crack was open quite a bit. It was a very snug fit when they went on. If I had to guess they are cracking due to it being too tight and when the metal expands from heat and it's running at a high rpm they crack. They do look beefier then...
Don't know what the issue with MMR is. I know there engine builds aren't that great or people who balance there rotating assembly but parts seem ok. Want to order Modular head shop 1200hp rotating assembly. Also have phenolic spacers and upgraded VMP intercooler pump to go in with mods...