I have an engine.....20-30 passes on it everything is pretty fresh. After pulling the heads and the cylinders have a good hatch but the thrust side of the pistons looks like scrapes on the cylinder wall.

Is this normal? everything is still pretty smooth......Should I re-ring it or is it o.k.? has good compression and everything else in the engine looks fine, I am just inspecting it while the heads are being reworked.

If I do need to re-ring it.....what are some good rings? The last set I just bought from the maching shop.....was a moly top ring file fit.

 

Pictures would be somewhat helpful - if you can catch your fingernail on any of the scuff marks you definitely need a hone. It's really one of those things you need to see in person, so have a machinist check it out.

 

I was just trying to get opinions from here.....I know it needs to be seen in person. You can't get your nail on it its slick, but only 20-30 passes I was expecting to see a better cross hatch there....it can still be seen but the direction of the piston can be seen.

I tried to take pics earlier but you just can't see it.

I have to take it to my machinist anyway to check P to V clearance and cut the intake to fit the heads...so its not too big of a deal.


Thanks for your help

 

Mine had the same thing at 100 miles. It is normal on the thrust side. Most will make a straight line down the cylinder wall, really more of a "polish" type mark instead of a gouge or scratch...at least mine was.

David

 

Thats a better description of what it is...more of a slick polish

 

You will see it more with short-skirt stroker pistons - 383?

If there is more wear than is normal you will need to look at piston to wall clearance and timing settings.

 

Whenever I see excessive piston/bore scuffing I check carefully for signs
of abnormal combustion. Mild end gas detonation can cause piston rock
leading to scuffing.

 

I will try to get a pic later........its hard to gfet a good pic with the lighting etc. of the area i'm talking about

 

If you shine a light on it you can still see pretty good cross hatch in the shiny area

 

I'd like to see a picture of the piston top at TDC. This may not be
practical, the spark plug insulator under a magnifying glass.

 

I have no idea where those plugs are..long gone.

 

IMO the most important thing here is to determine why the piston skirt is
rubbing the bore so hard. With only 20 runs what you are seeing is very
excessive. More than likely the problem is related to the tune up; either
detonation or too much liquid fuel in the cylinder.

 

I agree there was some detonation....I was trying to use a factory PCM....first tune bt pcmforless had alot of timing, Shon heron fixed it, but still had some, car would fall on its face out of the whole.

I have since gone to aftermarket pcm.....my question is do you think it is re-usable shortblock? The polished parts is very smooth no scuffs..so at the most I think it would just need a hone and some rings.......

 

Personally I would run the short block the way it is, ring seal should be
good. Some people won't agree and would disassemble it for an
inspection to look for other signs of damage, bearings, piston pins
and skirts etc. Get more opinions.

 

I wll do that.....I do think the rings are sealed good, the car picked up 2.5 m.p.h. from the first pass to the last, It did improve. My problem was never getting the tune right.

Also it was towards the end of the season(getting cold) so some of those 20-30 passes are only 1/8 mile