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Discussion Starter · #1 ·
Okay, the question above may sound a little stupid, but I have been thinking on this for a while.

Why? a stock cam rotates just like an aftermarket one. So unless there is something special about the stock cam (or 6.4L cam), then what is the problem with running an aftermarket one with MDS?

I thought all MDS did was lock open the intake and exhaust, and quit fuel and spark to the 4 unused cylinders?

I am assuming the knowledge I am lacking is either about the cam or MDS.

Any info is highly appreciated, Thank You.
 

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Okay, the question above may sound a little stupid, but I have been thinking on this for a while.

Why? a stock cam rotates just like an aftermarket one. So unless there is something special about the stock cam (or 6.4L cam), then what is the problem with running an aftermarket one with MDS?

I thought all MDS did was lock open the intake and exhaust, and quit fuel and spark to the 4 unused cylinders?

I am assuming the knowledge I am lacking is either about the cam or MDS.

Any info is highly appreciated, Thank You.
Q: Why must MDS be shut off with a cam?
A: It doesn't.

So. There you go.

That said, there are some (very aggressive) cams that do require disabling MDS. It may be the amount of lift, the overlap in the timing interfering with the MDS lifters or any of a number of mechanical issues I don't fully understand. You can get a great cam and keep MDS. (I speak as someone who has done just that.)
 

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Discussion Starter · #3 ·
I don't mean to make a problem, but do the 2006-08 5.7's have MDS?

I believe they don't, and if that was so, how would you have just swapped a cam into a car with MDS?

Is it a different car then the one in your signature?
 

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I don't mean to make a problem, but do the 2006-08 5.7's have MDS?

I believe they don't, and if that was so, how would you have just swapped a cam into a car with MDS?

Is it a different car then the one in your signature?
It all depends on the size of the cam. If the lift of the cam is more than the MDS can handle it must be shut off or you will risk damaging the lifters.
If you are getting a 6.4 cam for a 2014 5.7 make sure you get the cam from the MDS 6.4. You won't have an issue then. The early 5.7 car couldn't handle much more than 540 lift on an MDS lifter. Once the Eagle 5.7 came out and the lifter was redesigned that number went up to the .570 range. With the new lifters since the 6.4 came out it's higher yet. And yes, MDS has been in Hemis since 2004.
 

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Discussion Starter · #5 ·
What would the limits be for the duration of a cam in the 5.7 eagle, to retain functional MDS?
 
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