FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: plovett on October 23, 2020, 11:11:40 PM
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What does this look like?
pl
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To me, it looks like someone didn't deburr the bottoms of the cylinders. Could also be insufficient clearance.
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Agree completely, are you trying to reuse?
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That is a clearance issue. To high up on the skirt. Mike
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Ring lands look like very short run time. Skirts dry on install, not enough clearance, or dirty piston at install.
Do they all look like that?
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Ring lands look like very short run time. Skirts dry on install, not enough clearance, or dirty piston at install.
Do they all look like that?
I'll find out later today if they all look like that. Not very short run time. Several thousand miles, somewhere between 5 and 10K. The rest I am not sure about.
pl
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Yup, they all look like that. Not all to the same degree, but yes. You can see the corresponding wear on the cylinder walls.
pl
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Take a pic of the bottom of the cylinder.
If there’s a sharp edge there, it will roll the aluminum off the piston and then you get metal up in the cylinders.
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Take a pic of the bottom of the cylinder.
If there’s a sharp edge there, it will roll the aluminum off the piston and then you get metal up in the cylinders.
WILCO on that. I ran my finger along the bottom of the cylinders and it didn't feel like a sharp edge to me, but I will take a pic.
thanks,
pl
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Probably was one when fresh, just burnished itself over time...hard to avoid if you don't knock it down during prep
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Hard to get a good pic with the crank in there. I will take another one after it's out. The bottom edge of the cylinder feels "half-way sharp edged". Definitely not a large chamfer or radius there, but not sharp either.
The pattern is only on the thrust sides.
pl
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Piston skirt scuffing typically happens right away - on first fire-up. As mentioned above it can be due to dirt, a sharp bottom edge, or tight piston-bore clearance.
At Ford we did a lot of work with skirt coatings to eliminate scuffing with tight pistons. We were going tight to minimize NVH for future engines. Even though the coating would wear away quickly, it did its job in those critical first few seconds...
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Yes material will score up high on piston and cylinder from debris (should have explained better) but at the point of bottom dead center the amount of piston skirt out of a sharp edge cylinder will show a more pronounced area or scored harder usually at that point. Widest point of piston is around 3/4 of the way down but need to check you spec sheet as everyone is a little different. Pistons are not round nor are they tapered evenly, more like a offset whiskey barrel shape taper. The pistons in the pics are very evenly scored is leading me to believe it is a clearance or lube problem. This is just a guess from a pic though. Any crank scraper or screen stopping the lubrication on the walls? Most all rods are direction sensitive and yours are to as they have a oil passage to hit the thrust wall, any problems there? Just throwing it out there.
http://blog.diamondracing.net/how-to-check-piston-to-wall-clearance.
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I'd say Brent-o-bean is correct. This is the worst cylinder, number 5. It looks like a sharp edge and "scrape-age" occurred there. It might not be the only issue, but it looks like one.
pl
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Agree completely, are you trying to reuse?
Not reusing. Just intellectual curiosity...and mechanical prophylaxis. Not reusing pistons.
pl
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A lot of particles in those pics! I am not sure if that is just from the block being exposed or if they were already there. Going to take a closer look.....
pl
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The particles seem to be 99% leaf debris from my garage.
pl
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If they mic good no reason you can’t reuse Could coat or just let it be there for a little extra oil retention :)
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If they mic good no reason you can’t reuse Could coat or just let it be there for a little extra oil retention :)
Whole new rotating assembly going in. Just looking at pistons for information/learning purposes upon disassembly.
thanks,
pl
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I plan on boring the block, the minimum amount. It is currently at 4.155". I hope to go 4.165" if possible. I would go 4.160" if that would work.
pl
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Paulie, I'm trying to get caught up on your engine. Was this teardown from the concern about the valve lash moving every now and then? I spot what looks like an unhappy cam bearing in the last couple pics. Could explain why the lash moved and why the skirts got scuffed. I also agree a sharp edge on the bottom of the bores is a likely cause as well. Hope you get it resolved.
(https://i.postimg.cc/3Nbrz203/bore-ridge-b.jpg) (https://postimages.org/)
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I spot what looks like an unhappy cam bearing in the last couple pics. Could explain why the lash moved and why the skirts got scuffed.
A very unhappy cam bearing. That's a burred edge sticking out the side of it. Might have happened when pulling the cam out, but you can see the edge of the bearing is rolled over also.
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I spot what looks like an unhappy cam bearing in the last couple pics. Could explain why the lash moved and why the skirts got scuffed.
A very unhappy cam bearing. That's a burred edge sticking out the side of it. Might have happened when pulling the cam out, but you can see the edge of the bearing is rolled over also.
I've been looking at that, too. The cam didn't pull out easy. I didn't think much of it at first.
pl
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Paulie, I'm trying to get caught up on your engine. Was this teardown from the concern about the valve lash moving every now and then? I spot what looks like an unhappy cam bearing in the last couple pics. Could explain why the lash moved and why the skirts got scuffed. I also agree a sharp edge on the bottom of the bores is a likely cause as well. Hope you get it resolved.
(https://i.postimg.cc/3Nbrz203/bore-ridge-b.jpg) (https://postimages.org/)
The teardown is just to build a new motor. I didn't have a specific reason other than that. So these issues are pretty much academic other than I don't want the new motor to have the same issues.
When I pulled the cam it didn't come easy at first. There was some resistance and then it came easily. I didn't think much of it at the time. So I am not sure about the cam bearings. It looks like something was going on there, but I might've tweaked 'em more on the way out.
pl
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Well, I did have a "feeling" that I should tear this engine down, LOL! It has always run good, leakdown was good, etc. It's also been been run hard. I didn't keep track of the miles, but it's less than 10K, I think. I am glad I did tear it down now. It might have had multiple issues.
Thanks for all the comments and insight.
paulie
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That is a clearance issue. To high up on the skirt. Mike
Agreed, as generally a more defined parting line would exist at the stopping point the exposed piston skirting if solely a ruff edge at the bottom of the cylinder; and probably every bit as guilty is the compounding foreign particulate intrusion. ;)
Scott.
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That is a clearance issue. To high up on the skirt. Mike
Agreed, as generally a more defined parting line would exist at the stopping point the exposed piston skirting if solely a ruff edge at the bottom of the cylinder; and probably every bit as guilty is the compounding foreign particulate intrusion. ;)
Scott.
That makes sense. Thanks.
pl
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Respectfully to all those that have offered up opinions , what "I" see is "debris" in the skirts , with the second ring as the probable source as it looks to be 50% or more worn. The "bottom of the bore" is often a source of mild scuffing BUT normally leaves a whitness "line" LOW on the piston as only a half inch or LESS comes out the bottom of the bore. The scratches showing go farther up the piston and are small grooves as most often associated with "foreign matter". It seems also to be limited to below the rings , leaving out coming through the carburetor because of a lack of air cleaner. The multiple narrow scratches are not consistent with clearance scuff or "black death" caused by literal melting of the skirt material that turns black and is "smeared" looking.
"I" would look at the ends of the rings for a shiny spot that indicates the rings were butting. My opinion is from my 30 years in the aftermarket custom piston business and looking at thousands of damaged pistons for "root causes" , which I still do everyday.
Randy
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I am far from an expert but but what Randy said matches my findings on my pistons when there was metal in my oil. Motor was spotless on the build but the dizzy gear depth was wrong and sent iron through the system along with other metal material. Not nearly as bad as yours but strikingly similar and with only dyno time. Just another opinion.
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I'll add that the pistons are not "scrap bin" parts as the skirts could be hit with Scotchbrite and coated to be perfectly usable. I wouldn't say that if they had "black death".
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Good info on both posts Randy...I agree, I'd either clean them up, or clean them and coat them if you wanted to be fancy :)
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I'll add that the pistons are not "scrap bin" parts as the skirts could be hit with Scotchbrite and coated to be perfectly usable.
Just to expound on this: The procedure which has proven to work well in salvaging pistons in this condition for us has been to glass-bead (new clean material please! ::) ) the damaged skirts, this beats down the crowns of the peaks pushing some of this material back to a useful placement, also tends to work well at lifting out the foreign particulate impinged in the surface, and tends to "fluff-up" through the peening process the surface thereby blending and recovering some of the lost diameter of the piston, and then yes, "Scotch-Brite" the surface, by hand (no flap-wheels & drill motors please! ::) ) thoroughly to remove any impinged blasting media, and to smooth and lay down the surface additionally. This is not difficult but does require some technique in order to acquire pleasing results. And yes the further inclusion of a coating process is a nice option but necessarily a requirement for function. :)
Scott.
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Thanks guys! I have no plans to reuse the pistons. I was just asking for the sake of knowledge. I guess I won't throw them in the scrap bin or melt them down just yet, though.
pl