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2004 GTX
32 Posts
what is GM's stance on the matter, do you know?
They are in the same boat, can't fix the heart of the issue , because it's an emissions control function, you can make the system tighter , can't make it " looser ,

For the Hemi it's the VVT system and the different ramp rates for the MDS and "solid" lifter..I use the term solid only because it's the lifter that doesn't bleed down.

I'll touch on some of it here,
The MDS cam, has two different ramp rates one for the MDS lifters and one for the "solid lifter" there is also a slightly different lift, between the two(495Vs 490...If I remember correctly) so basically 4 cylinders have one cam profile and 4 cylinders have a different one..........
All the warranty claim info that was shared with us(and CFI Ric's company) stated that NON-MDS system vehicle failures (09-13) were due to 1) wrong camshaft 2) there was bad run of valve springs and 3( my favorite) some of the NON-MDS engines received MDS lifters. FCA was not prepared for the demand of sales in 2010-2012 so in order to complete sales some MDS Long blocks found their way in HD2500/3500 trucks. I heard of run of 200 consecutive vin HD2500 that had NON-MDS lifters in MDS trays , which causes a different issue all-together , the lifters turn slightly in the tray and don't ride true on the lobe.

The early engines had two different opening/closing rate valves springs, the stronger spring was to be installed on MDS cylinders to,
1 help the blead down of the lifter.
2 keep the lifter from "skipping/bouncing" across the cam lobe during what is called Low lift duration.
EDIT: the 5.7 stick cars were not supposed to get the 2 different spring rater springs, the ones that did were prone to wiping out cams, because the lifters under the softer springs would bounce off the lobe in higher RPM situations.

Low lift Duration happens when the ECO light goes off and the MDS lifter pumps up.
the srt392 stick cars that have had issues, was a bad run of cams.
I'll touch on the oiling issue tomorrow.

Proud Canadian
208 Posts
Discussion Starter · #22 ·
And issues with their direct injection system. My neighbor's newer Chevy has spent more time at the dealer than he has actually gotten to drive it lol.

by the looks of it, in a few years he won't take his new Chevy to a mechanic, he will take it to an electrician instead :sick:
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