Happy holidays moparts folks!

I am going to check the lash on my new .557 MP cam and it got me thinking-
I set solid cam lash on Harleys and slant sixes for years and never had such a large lash spec as the .557 cam (in the neighborhood of .030!)

To a certain extent it makes sense to provide assured clearance despite heat expansion, and I understand that the slow ramps of the old MP designs won't beat up the valvetrain like say a violent solid roller. My MP 557 runs about how I expected- soft and smooth with a violent top end like a fat girl on crack. Nice typewriter/sewing machine noise, but no radical clackityness.

I know the lash can be experimented with and can indicate a too big or small cam if it helps to add or remove lash. Did MP make a nasty cam on paper and tone it down for the actual target audience with a huge lash? Would it self destruct with .010/.017 lash? Is it beating the tar out of itself with the big lash spec?

When and why does a grinder recommend more lash than strictly needed to ensure a closed valve on the heel of the cam?

Can`t speak for the Mopar cams but I`v always ran my Isky up as much as .010-.012 tighter and never had any issues and they called for .024-.028 hot.

This is my 2-cents (opinion), FWIW.

The lash is a large function of how the beginning and end ramps on the lobe were shaped (ground). That being said, some variation is tolerable. I wouldn't run a cam speced at 0.016" lash at 0.028" for any length of time (just a test). And a cam designed for 0.028" I would like to make no tigher than about 0.020"

On that particular grind (MP .557"), many people have run them around 0.024-0.026".

One other consideration. The lash will change as the engine heats up.
- Exhaust valve might need 0.002" more lash for the same ramp
- iron block, iron heads cause lash to tighten with heat
- iron block, aluminum heads cause the lash to loosen with heat, typically 0.004-0.005"
- aluminum block, aluminum heads and you might see 0.020" change from 50F to 200F.