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Piston and cylinder damage
So, I found this on an engine I am looking to reseal and have the heads done. Looking for advice or opinions on what the downside is to putting this back together as is. Or other input. So, The cylinder definitely ate something. Pits and dings on the bottom side of number four piston with Gouges on the piston wall. The gouges are the black marks. Was unable to get reliable leak down test. Aside from the dings on the piston, it looks no different from the others with carbon buildup. Thanks https://cimg0.ibsrv.net/gimg/rennlis...857a1c2ef.jpeg https://cimg9.ibsrv.net/gimg/rennlis...bc4d9fa3b.jpeg https://cimg1.ibsrv.net/gimg/rennlis...ba5512131.jpeg https://cimg2.ibsrv.net/gimg/rennlis...bef459b4a.jpeg https://cimg3.ibsrv.net/gimg/rennlis...c9d125d66.jpeg |
The dings and gouges are in mostly harmless places that could be easily fixed by decking the block, even if you don't the fire ring should take care of it.
The scratches aren't unusual but if you can easily catch your finger nail in it you should either machine that cylinder to the next size piston or get a new block. You definitely need a new piston though. |
Personally I would look for another shortblock. Talk to Mark..
I say shortblock because then you know bore and deck condition. Worth checking bottom end and crank endfloat on any replacement candidate too but I am sure Mark can help with that... |
Agree, get another short block.
Checking with a boroscope would have shown this damage prior to buying it. |
But I now like to see the deck area as well having bought a car with eroded deck previously...
https://cimg9.ibsrv.net/gimg/rennlis...ce7a3fd7b4.jpg |
I did not notice this until after it was cleaned up. I have doubts that it would have been seen with a borescope.
Possibly, but I am looking forward at this point. Appreciate the input. |
That would be easily visible with a good average scope.
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One of the pix is the cylinder prior to cleaning. The wall scratches are visible, but not the piston dings. |
Well, unfortunately my machinist concurs. Need a new block or sleeved. That was not the answer I was hoping for. |
Originally Posted by firemn131
(Post 15671335)
Well, unfortunately my machine is concurs. Need a new block or sleeved. That was not the answer I was hoping for. |
What year engine are you looking for?
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This is my extra engine for my 87. |
Originally Posted by firemn131
(Post 15671422)
This is my extra engine for my 87. That 87 is fighting you tooth and nail throughout the duration, isn't it? |
Well, I can’t really complain it’s been a daily driver for eight years and The thrust bearing damage was done well before I took ownership. So the fact that I can still drive it every day is a testament to how robust the engines are. I am a bit frustrated now because I had a full head of steam to begin the build process. It will all work out just a little bumpy along the way. I will tell you, that if it wasn’t for the great support of this forum and all of the vendors I wouldn’t even consider any of what I’ve done so far. I really do feel pretty accomplished in what I’ve had to do so far. at this point I am debating on starting on the black 89. I really wanted to get the red car back on the road. I guess right now I am in a holding pattern until I hear what options I have from the seller. God is good, it will all work out. |
Getting a "perfect" core engine, ready to install rings and bearings is getting to be extremely rare....after all, they are all 25+ years old, now.
It's my opinion that selling/buying a "good" engine is foolish, these days. I'd be selling "unopened" used engines as "rebuildable cores"....only. That's what I always hope to get....something I can rebuild. Fortunately, Porsche still has 1st oversize pistons (100.5mm) available for the S4 engines (the only pistons they have for '85 and later engines)....and they are not "mega" bucks. I keep a set in stock, at all times, so I don't have to wait for pistons to come from Germany, when someone needs a set. Bore that thing and deck the block. Brand new. |
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