Re: [AMC-List] AMC six ignition timing -- got it!

["Swygert, Francis G MSgt 436 CES/CECM" <Francis.Swygert3@xxxxxxxxxxxx>]

> fine. NO ping at all, I had it in to keep engine temps down as
> my shortblock is a warranty pull for piston noise when hot,
> so I thought I'd keep it cooler and see what happened. I've
> never heard said piston noise and enjoy my "free" 4.0L greatly!

Wow, that's weird. Some piston scuffing a wall when hot?

-----------------

A machine shop tech who rebuilt a lot of warranty blocks for the local
Chrysler dealer when I was in Warner Robins, GA, told me that the
factory piston to wall clearance on the 4.0L was something like 0.020".
They discovered that when the clearance was increased to 0.040" there
would be a piston "tick" due to the skirt rocking a little, mostly at
low speeds (more at idle than anything). It would generally go away at
highway speeds, but could have been other noise masking it. This
occurred on a lot of low mileage 4.0Ls made in the early to mid 90s --
shortly after Chrysler took over. The permanent fix was coated skirts
and some additional webbing for the 96 and later engines. Could be that
as the engine warms the clearance increases in Mark's engine, but
doesn't increase enough to cause a discernable noise under 200 degrees
or so. A lot of people "in the know" bought relatively low mile
Cherokees in the mid 90s from owners who were still worried after being
told the engine noise was normal. Those who were leery dumped 40-50K
mile Cherokees at good prices! 

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