Okay to drive on a wiped cam. 5.7l hemi

[flipper35]

Originally Posted by Jeff Higgins

Wow - that sucks. So the heads capture the lifters underneath them? Whose clever idea was that? I'm having a hard time imagining any advantage to such a design.

Might have something to do with the bar that blocks them out for the MDS as well.

[Jeff Higgins]

What is MDS?

[gordner]

Multi displacement system. 8 cyl becomes 6 or 4 depending on requirements.

[stevej37]

[QUOTE=AZ_porschekid;10805668]BIL wiped his cam and one lifter on his 13' hemi 2500.

Sorry that I am slow/behind the times. But what does 'wiped' mean?

[asphaltgambler]

The individual cam lobes are 'egg shaped' and when the micro hardness surface layer wears through the lifter bottom (flat tappet) and lobe start to wear against each other until round. Doesn't take too long and all those filings get picked-up by the oil circulation and before long catastrophic damage.

[stevej37]

so...the problem is from the factory?

[Jeff Higgins]

Originally Posted by gordner

Multi displacement system. 8 cyl becomes 6 or 4 depending on requirements.

Wow - I thought that particular bad idea had gone by way of the dinosaur when the Caddy proved to be such a failure. Shows you what I know about newer cars and trucks. I just don't stay current... maybe because so little of it interests me...

[unclebilly]

Almost all modern pickup trucks have variable displacement engines of one form or another...

GM and Chrysler are MDS which knock out cylinders when the power is not needed. Ford has turbo charged engines that have a constant displacement but the turbos and engine management system controlled fuel injectors pack in more or less air and fuel to result in the required amount of horsepower based on driver inputs. Toyota still has the 5.7 liter from 2007 with no gizmos... until late this year when it is rumored that they will have a hybrid drive system like a McClaren P1, Porsche 918, and Ferrari LaFerrari... small fuel efficient engine for cruising and combined electric / internal combustion for when the power is required...

[gsxrken]

I’m hearing more and more about the lifter failure. My 2011 has 70k on it. On the other hand, outside of the P- tax world where rings can cost $140 per cylinder and pistons/cylinders are $4500, you can get an entire rebuilt Hemi engine with a 5 year warranty for about $4k. Pain in the ass but doable.

One example of many:
https://www.powertrainproducts.net/Dodge-5-7-Engine-Hemi-2009-2016-W-MDS-p/1365b.htm

[asphaltgambler]

Originally Posted by stevej37

so...the problem is from the factory?

The faulty lifters, yes. For some reason the 6.1 engines ( SRT8) of the same era do not. We have one with 170K on the clock all good. Back in the mid-70's GM was cost cutting every way possible. One of which was not heat treating their camshafts as much therefore the microscopic layer was 'thinner'.

Problem is if the engine ever ran hot or oil changes became neglected the hardness would wear off and the lobe(s) would 'wipe'. Usually on the rear cylinders / exhaust lobe. So when that happens the exhaust valve barely opens and the subsequent explosion / mixture goes back up into the intake manifold. The more you open the throttle, the worse it runs.

[stevej37]

^^^ Ok ...thanks for the explanation.

[Brando]

I'm guessing MDS failure and it is eating up the cam. Search on any of the Ram forums and you will see threads galore about reversing the damage or disabling it to prevent failure.

Find a rebuilt long block, transfer the accessories, get MDS disabled with a tune, and drive it until the next catastrophic failure.

[asphaltgambler]

There are problems across all makes with the 'variable' displacement. GM / LS series suffers piston oil ring sticking and sludge. When running the cylinder that 'deactivates' runs suddenly cooler as there is no fuel and little pressure. But hot oil is still splashed up onto the cylinder wall but now the oil ring ( lowest) is 'cold'. Frequently it leads to sludge build-up. Then slowly the sludge starts to pack the oil ring / land and then prevents ring 'float' and drain back. Soon liquid oil is getting past the oil rings and creeps into the combustion chamber. Rapid oil consumption, plug fouling and emissions system damage follows.