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

[Mark Price <markprice242@xxxxxxxxxxxx>]

I never really tried to figure out exactly what was up with the noises cause. The guy that gave me the shortblock said the noises usually occured when the Jeeps were HOT, up around the range the cooling fans cycled on and off. I figured with the larger grille area in the American, I'd try a 180* t-stat and see what the reult was as I could see the bores and they were spotless, with no scuffs of scratches evident. I knew th eowrst I would do is have a piston or other engine rattle.
  The engine in the American is not as noisy as the one in my wifes 97 and it is supposed to be the "new" engine!

--
Mark Price
markprice242ATadelphia.net
Morgantown, WV


---- "Swygert wrote: 
> > 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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