Zippy, I had the understanding that the latest aluminum heads sold by MP with standard valve sizes were “fixed”, meaning they had no issues as the earlier ones did. Date codes on the packages were around 2012-2014 I think. Have you heard this or not so?
I had Edelbrock made MP Hemi heads in the shop a few years prior to 2012....... so it would seem the heads like in the pics should have been out of inventory by then.
Zippy, you’re correct on the stock iron head flow. Original, unmodified 559 heads flow in that 300cfm range.
Funny thing....pretty much everything I had access to that was tested either at the CTC airflow lab or at Arrow racing engines matched up (within a handful of CFM) to flow numbers you've posted, fast68plymouth. I remember noticing that and going "well, it's basically like a lightweight stock head then."
The transition from the 110-M to the Edelbrock-manufactured 110-M1 (someone had a sense of humor with the casting number) began slowly in the 2008 to 2009 range under the same management regime I worked under/same one that replaced the megablock with the world block and did alot of other good, but because these parts don't exactly fly off the shelves and not much of anything was really advertised.... not everyone noticed the 110-Ms had been replaced. Took awhile for word to get out.
Edelbrock layed the option of a higher flowing head on the table, but my management decided to stay with something close to oem replacement. I'd have to guess nobody was ready to open that can of worms.
Don't forget..... MP used to get yelled at all the time by non-racers, for things like 509 cams being used in otherwise 100% stock vehicles (which brought on the wide LSA version, better idle but kind of a dog, and a poor seller), Hemi blocks with wedge motor mounts ("now my exhaust won't fit! thanks alot, pal!")......The last thing anyone needed to hear was "where did all my torque go? I put your $3000 heads with giant intake runner volume on my stock 426, and........"
