I wonder how many Hemi engines the magazine writer has disassembled and fixed? My guess is ZERO! I have done a hundred cams and lifters in them and no issues with the MDS lifters ever. I just finished one a couple days ago in my 3/4 ton 5.7 (and many other 3/4 tons) or 6 speed cars that didn't even have MDS, I would like to hear how MDS ruined those... Never have I personally seen a bad MDS lifter and very few pictures on the google machine, most are the non MDS lifter and a lot of miss labeled pictures showing non MDS lifters claiming they are actually bad MDS lifters. I bet the magazine writer can't produce a picture of one either he personally took out of an engine. I have also never seen an MDS solenoid get stuck or go bad in any form. I will not say that there has never been a bad MDS lifter or solenoid butt there is definitely NOT a "common scenario" where they go bad, not even close. The scenario he describes is a lot more like what happens in the chevy AFM engine. They go bad because the needle bearings inside the roller wheel are too small, when they switched to the bigger needle bearing in the lifter the failures quit.
I'm going to agree and Disagree with Dave here, 95% of the lifter failures are the NON-MDS lifter........ there was an issue in 15 where MDS lifters where failing due to needle bearings(hence FCA"s "FIX" call all new lifters Hellcat lifters"...marketing it's wonderful thing. )
the failures are due to a combo of issues ,most of the early failures can be linked back to bad valve springs(inconstant valve spring pressures) some too weak to hold the lifter against the Cam, which allowed the lifter to bounce, some too strong which drove the lifter into the lobe.....once FCA realized what was going on spring manufacture was changed, and we all know that it didn't stop the issue...but it cut back the under/over 100Kmile claims by due to lifter failure by 45%
Oddly 09-11 failure rate was 1 in 38k units it went to 1 in 12k between 2012 and 2015, now it's back to 1 in 38k ..it is a problem but GM rate with their D.O.D system is 1 in 15k
For those who don't know the lifters galley is divided in to 4 sections....the oil passage from front to back of the block has a "wall/divider" between the front and rear section on each bank. each MDS solenoid controls 4 of the 16 lifters.
HOW MDS ruins engines... "danger zone" is when the ECO(MDS) light comes off and the engine enters "low lift mode"(between 11MPH and 20 MPH) before the oil pressure " fully pumps up" the MDS lifter. at this point the MDS solenoid is opening and closing depending on throttle demand under 20MPH it's proportional to Throttle demand ,3.79v /full throttle opens the solenoid fully ...after 20 MPH the systems reacts to throttle request differently , it becomes more aggressive in it's opening rate per Throttle request based on RPMs above 1800/1900, it's different per model and engine. but it's roughly anything above 2.10V of throttle request ..(.side note it's the only good thing about those pedal commanders)
When in ECO(MDS activated) the only oil getting to the lifters is from the rocker gear, , the MDS lifters bleed oil out the hole and it runs down and lubes the roller..., the NON MDS lifter's roller only gets trickle down oil from the push rod seat in the top of the lifter...basically what ever seeps past the diameter clearance....In essence till that Solenoid opens up it's being starved for oil...may only be nano seconds...but if that sticks....those 2 NON-MDS rollers in the section of block are going dry.
When in standard operating mode, the lifters are feed from both the rockers and the main oil galley. there are 4 passages that come off the main galley to feed the rocker and Valve gear , about half way up they break off in to a Y which is empties right under the MDS solenoid and feeds the lifters like an Old SB/RB/G2 hemi....or like almost any other V engine ever designed.
Now if you change to a NON-MDS cam, you should remove the Solenoids and replace them with the plugs.....the tips of the solenoid may not be much of an obstruction in the passage, but why have an obstruction when you don't have to.
Now the trick........If you are building a G3 from scratch..........Grove the lifter bore (comp cams has a nice lifter bore grooving tool for the .842 DIA lifters)
And for the record I completely disagree with the " the larger Needle bearings solved the issue comments........the 03-08 5.7s & 06-11 6.1's all used the same NON-MDS lifter and the increase in cam/lifter failures didn't start till spring manufacture was changed in 2012 .....needle bearing change happened in 2015 with the hellcat lifters and went across the board in 2016 and still have the same failure rate as pre- 2012
