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12 Posts
Discussion Starter · #1 ·
I had my machinist build a new 4.6L for my '97. Probe pistons were a less-expensive forged piston than good old JE, and used a "low-expansion" 4032 alloy. They recommend piston-to-cylinder wall clearance in the range of .0015" to .0035", instead of the .004" to .0045" that you might used with a 2618 alloy forged piston.

So I fire up my new more powerful engine and take it out for a run. After about 400 miles, she starts developing a rattle in the bottom end. Not good. We pull the engine out, and guess what? The pistons are scuffing!

For my naturally aspirated, heavy duty towing application the brain trust at Probe Pistons recommends .0025" clearance. Foolishly, the machinist and I accept their recommendation. It was obviously too tight, and they were fatally wrong...

Yet who pays the price for their bad advice/lack of knowledge? You got it. Me. No new pistons will be forthcoming from Probe Industries, in Torrance, CA. Despite having the irrefutable evidence in front of their beady eyes, they slander my machinist with foolish statements like "improper assembly" or "contamination" with absolutely no indication of this having been the case. All the evidence points clearly to incorrect cylinder wall clearance. But do they make any attempt to compensate the wronged customer? Nope.

Watch out for Probe Industries. You should not trust your engine to them.

12 Posts
Discussion Starter · #2 ·
Here's a pic of what it looks like when your piston clearance is set
.0005" to .001" to tight, based on the recommendation of a
disreputable piston manufacturer.

Although viewing a picture is not the same as dragging your fingernail
over the grooves galled in the cylinder walls, the photo still shows
the darkened area in the bores where these grooves lie. This area is
coincident with the widest part of the piston skirt. There can be no
doubt that insufficient clearance caused this hard contact of the
skirts alone as the piston expanded under hard use.

Probe pistons scuffed 4.6L cylinder bores

The ring gaps didn't butt closed, it wasn't shiny on the ring ends and
the rings didn't gall into the cylinder walls. The cylinder scoring
is in the piston skirt location. The engine had high compression, no
blowby and more power than stock.

The engine had oil pressure. Bearings were good, except for some
embedded metal particles circulated off the cylinders. Bores were
checked before assembly and after the disaster for diameter and taper.
Clearance was .0025" to .0027" top and bottom, all 8 holes.

This is a '97 4.6L SOHC Ford Crown Victoria. Probe Industries
recommended .0025" clearance as their pistons use a "low-expansion"
4032 alloy, and I wasn't running a supercharger. I explained I would
still be using the engine at full throttle for extended periods on the
occasions when I tow my boat, and specifically asked if that wasn't
enough abuse to warrant extra clearance. They still insisted .0025"
was enough clearance, only blown motors needed .003" - .0035". Not
wanting unnecessarily rattling pistons, my machinist and I accepted
their advice. They actually list the clearance specs on those pistons
as .0015" - .0035". Ford cast piston clearance is .001".

They were obviously wrong, and refuse to admit their mistake, replace
the pistons, refund my money, or even return the damaged pistons I
sent back to them for their "inspection". They could offer no
explanation for what happened. I talked to the owner. He is

I would definitely not recommend buying pistons from Probe Industries.
I have had good luck with JE, CP and TRW.

- Lifespeed scoring sm.jpg

12 Posts
Discussion Starter · #4 ·
The pistons were correct for the 4.6L. The clearance specification was incorrect. This is traditionally supplied by the piston mfg, based on intended usage.

Yes, I sent them all 8 of the pistons at their request for inspection. As of yesterday, I heard they sent the damaged pistons back to the distributor I bought them from. Not that it makes much difference, their mistake still caused me to build this engine twice at huge expense.

They refuse to refund my money, replace the pistons, or admit they were wrong. Of course, Probe Industries has no explanation as to what happened. They're just certain it wasn't their fault... Doesn't look that way to me, or any other experienced machinist. I've reported them to the Better Business Bureau (2nd complaint on record), sent a nasty letter, but not an attorney letter. Would be small claims territory, anyway. Don't buy Probe pistons! There are alot of quality mfg's out there, like JE, Ross, CP, Manley, etc.

Now, I'm not waiting on these jokers to get my engine back in my car. I've got a new block, CP forged 2618 alloy pistons, and the block honed with torque plates to .0035" on CP's recommendation. Should be back in the car by the end of the week.

- Lifespeed

Silkwood said:
Ok let me get this straight... they sold you the wrong pistons, even after you persisted that it might be tight. The pistons were wrong, damaged the block, and wasted your bore job, gasket set, bearings, labor and of course, the pistons. You sent them 2 or more of the failed pistons so they could inspect them. Now they won't replace the pistons with the correct ones, nor will they refund your money, nor will the even return the failed merchandise you bought from them?

Did they ever admit fault?
Did THEY request that you send in those pistons?
Did they tell you they werent going to return the pistons you sent back?
Are they offering ANY suggestions for recovery?
Have you checked for a Better Business Bureau or the like in the area of the company?
Do you know an attorney that would at least send a letter suggesting to the company that they cooperate with you? Attorney letterhead is pretty potent stuff.
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