[GMG_2743]

Below is a quote from fargo59's post on the new 5.7L Hemi code named 'Eagle'.

"tappets: i wouldn't normally cover this, but i actually made notes in class because of this. they have been revised for higher lift with proper MDS actuation. the stock cam lift now is approximately equal to that of the spartan/sparrow cams currently available. both of which are supposed to be the border line of MDS capacity. the new lifters do this constantly in factory form. further more, they are backwards compatible. they will drop right in to an older 5.7 (or any previous hemi built with MDS)"

Link

Has anyone thought about swapping out all of their current lifters to this newer version when doing a cam swap to a spartan or cam with similar lift? I would think this would give increased reliability as the spring will not be compressed as much.

Going further does anyone have any idea on what a full set would run (if you can even get one)? Would push rod lengths need to be altered as well? In that thread the push rods are also supposedly ~4mm longer. My guess is this is due to head design changes as the new lifter design I would think would decrease the required push rod length if anything.

 

[392Stu]

I have some coming in to test. I'm pretty sure this will require different and probably custom pushrods though.

 

[rander]

Keep us posted stu. BTW, what gains do we get out of this? More lift with the cam we already have?

 

[monty1269]

opcorn:

 

[GMG_2743]

I'm not the engine guy here but I don't think you will see any gains at all just swapping the lifters out (all other things being equal). The only way you would be able to make gains would be if the newer version has less friction losses in regards to the rollers on the cam shaft. Which I highly doubt and the gains would be negligible.

What these lifters could allow is larger lift cams. I am basing this off of the other parts of the post about the new cams having lifts similar to that of the spartan and other cams.

This comes from the following idea.
The limiting factor to lift and retain MDS is coil bind in the MDS lifters. The spring in the lifters must be able to "absorb" the maximum lift of the cam without opening the valve. From the factory the max. lift of the cam only used a percentage (say 60%) of the maximum amount of spring travel to coil bind. Cams like the spartan that retain MDS use up more but not all (say 90% of spring travel to coil bind).
Going further with the new cam having a larger lift than the spring in the lift would be longer to retain the 60% (of travel to coil bind) number. This means that cams with even larger lifts or cams currently out there could be MDS compatible when used in an 09+ 5.7 hemi w/ MDS or possibly an earlier 5.7 MDS Hemi depending on the compatibility.

Further:
The reason I possed this question is reliability. The further you compress the spring in the MDS lifter the more stress you put it under. The factory is/should be concerned with reliability and longevity so they only compress the spring a certain percentage. From an engineering class I took in college (Mechanical Engineer) I recall something like 60% of coil bind and a spring is pretty indestructible. Beyond that the life "can" be shortened depending on the quality, care, environment... As with anything if the spring has a flaw when it is formed it can fail under very little stress or travel.

I purchased a spartan and big valve heads from stu last summer but never got around to installing them because of job & personal stuff (I moved and got a new job). Given the economy the original idea of getting a daily driver and leave the charger for weekend and nice weather fun is not in the cards in the near future. I still want the extra power but if I can add a bit more reliability I will when I have the install done.

 

[rander]

I read some where that if we were to use these or similar rocker and lifters we would get closer to our true cam intake/exhaust lift.