383 LT1 thrust side wear
 

I'm in the process of tearing down my fairly fresh 383 (Maybe 3k miles) because I was dumb and tweaked the oil ring on cylinder #1 while installing it and still put it in. Here's my issue, the thrust sides of the cylinder walls have worn down the cross hatching on all cylinders. (pics below)

This is Scat 9000 series crank, Scat 5.7" Pro Series I-beams, and Mahle 4.030" forged pistons. Too much fueling/washing out the cylinders? (spark plugs are coffee brown)

This wear is the same on EVERY single cylinder.

My plan was to re-ring cylinder #1 that was burning oil and have the assembly balanced again (because of a weird vibration at 3-4k rpm) and put it back together.

I don't remember the exact clearances but I have an LT1/LT4 rebuild book and all the clearances came in where they needed to. I know I have read that a 5.7" rod 383 can cause more thrust side wear than a 6" rod 383 but this seems excessive to me.

What do you guys think? The car ran great, never did a compression test though.

(these pics are from cylinder#5 although all the cylinders have VERY similar wear)
https://cimg3.ibsrv.net/gimg/ls1tech...f9de6db77f.jpg


https://cimg0.ibsrv.net/gimg/ls1tech...22825b6cb4.jpg

yeah a 5.7" rod will cause more side loading...which is why many, including me, used 6"...I have over 40k mi on my 383 build ...YMMV

I pulled all the pistons out and they all have the corresponding wear marks on the skirts of course. They just looked scuffed a bit. Rod bearings show some dirt/dust from reassembly but no gouges. What is everyone's standard for replacing rod bearings?

From the research I have been doing I guess cylinder marks like the ones I'm seeing are fairly common. Usually they are on cars with quite a few more miles though. The general consensus seems to be just put it together and run it.

You should measure the bores. Wondering if the pistons are rocking...

If the pistons were rocking wouldn't the wear be on the edges of the skirt and top of the piston? Basically the bottom and the top of the piston?

dunno. wouldn’t hurt to measure them and find out what the tolerances are supposed to be between cylinder wall and piston skirt.

The problem I have now is I don't have my bore gauge. My buddy has it as I didn't think I would need it. It's not easily accessible as he's 4 hours away and needs it himself. hmmm... I don't really want to buy another considering how little use mine gets as it is.

I don't have an easy way to bring the block to the machinist either. Everything is working against me! ha :)

Of course my micrometer is not "deep" enough to get down into the bore. I can only measure the top 1" of the bore.

Well screw it I ordered one of the cheap bore gauges on amazon. From the wear I'm seeing it looks to be piston to wall clearance issues. I'm surprised because all the specs were lining up fine. Pretty sure I would have remembered if a spec came out wrong.

Now I'm wondering if I can just hone the cylinders and re-ring all the pistons and be ok. No idea how much material the pistons took off the cylinder walls. Maybe just enough to solve my clearance issues! haha

Here is a piston pic. All the pistons have the same wear pattern. Also no deep scratches, just wearing down the coating on the skirt.


https://cimg4.ibsrv.net/gimg/ls1tech...d7816a9e1f.jpg

https://cimg7.ibsrv.net/gimg/ls1tech...b8e4af512e.jpg

The triangle wear pattern is interesting.....what does the other side look like? Or are those two pics showing both sides of the same piston? If so, makes me think that the clearance was too tight(since pistons are smaller at the top than the bottom)....but I'm no expert engine builder.

I'd ping a good engine builder with those pictures or call the tech help line for the piston manufacturer and send those pictures.

Have a look at these....

I decided to take everything to my local machine shop. He said he is going to take a look at everything to try to figure out what happened but he seemed to think it was incorrect clearance between the piston and cylinder wall.

Th nice part is the cylinders aren't too bad so I might be able to get away with a hone and new rings. Fingers crossed!

I will update once I find out more.