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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Just curious if you more experienced builders would be concerned about these vertical scratches appearing on the thrust surface of the cylinder wall, 100 miles after a rebuild.
And here's an image of a gouge on the top of my front piston, which I'm really hoping happened during assembly:
Did you install new pistons or just re-ring the existing ones? If the list in your signature is what you used than my question is answered, new. It may just be the view the scope give ya but that second shot sure looks like theres been small debris bouncing around near the center of the piston.
Maybe it's nothing to worry about - which is what I'm looking for opinions regarding. I'm hyper alert to any issues with these pistons and cylinders because this is the 2nd set, the first set having been taken out within 500 miles from galling. There was no clearly identified cause last time around, and I'm watching this like a hawk this pass.
Correct, pistons, rings and cylinders are all new, S & S 100" kit.
Just make sure no one glass beaded anything that is part of the intake system or has contact with oil. I've seen too many cases in my days of engine work where we do a long block for someone and they bolt on an intake manifold, valve covers or any tin ware they glass beaded. Then the glass medium gets where it shouldn't be.
I think you are washing the piston with gas, and those specs are from detonation. I would start by putting all the timing to 0 in the map. Did you get your afr gage yet?
Last edited by xcbullet; Aug 27, 2018 at 05:30 PM.
Going to assume that is fresh crosshatch from medium grade stones. That is in my opinion, the rings just deburring it. The crosshatch is so shallow, it's not measurable. I am sure the grit size can be translated to depth. I saw similar on my Jeep I just rebuild. I used cast iron rings on unbored cylinders. So I used new medium stones with gasoline for a lubricant to make them rough but not take any more out. Probably did not hit them running slow more then 15-20 seconds.
By the time I got pistons in and rotated a few turn, I saw the same thing. Not an expert however. I have rebuild a few dozen engines.
If you look close, most crosshatch scratched are still visible under the shadow. So those scratches are microns deep. Why I think the sharp burr edges of the crosshatch rolled over. You could not detect that with your fingernail.
Think medium is 265um. Not sure how to translate to micron
Last edited by Jackie Paper; Aug 27, 2018 at 06:27 PM.
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inspection scope pic of cylinder wall and piston
