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Cylinder Wall Scoring

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dsm-junkie

10+ Year Contributor
277
1
Jan 20, 2012
miami, Florida
Hey guys I have a question! Heres some pics of all 4 of my cylinder walls! You can see where there is scoring! Now is this considered bad? Should I have the block honed?? The member I bought the short block claimed that there was only 25 driving miles and only a few hours of idle time! Does this look like he was telling the truth? I also did a compression check when I had the motor in and the numbers were super low! 70 psi in cylinder #1 and 65 psi in #'s 2,3, and 4! It did have a new OEM head gasket! I couldn't do a leak down test! :no-good: So I took the head off and the camshafts out and all the valves were seated fine! I did the water test and all valves passed! So my final conclusion would be either timing marks were off or I have bad rings! What do you guys think???

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Well a few hours idle time on a fresh motor is a good way to screw up the ring seating process.

There has been too much contact from the skirt to the cylinder wall. Can you drag a fingernail across it and catch it? It appears to be from incorrect PTW clearance.

Can you drag your fingernail up the bore and catch a ridge at the top of the cylinder? It looks to have a lot more than 25 miles on it IMO. Mine had 18k and the top of the cylinder bore was still clean.

You need to measure the pistons and the bores and see what the clearance is. I would say you are going to need to rehone it at the least depending on how far off the PTW clearance is from spec.
 
^^ Thanks a lot for the help guys! I came to the conclusion that I am going to rip out the pistons, rods, and crank and get a stock 6 bolt short block from a friend. I am gonna send it to the machine shop and get it bored .20 over and get it all right then just throw my existing rotating assembly into it! (After inspecting it all) Im most likely gonna trash the short block since its a non turbo block anyways! :ohdamn: Such a waste of time and money but hey...No pain no gain!
 
Please update this thread with what you find for future reference. ;)



Oh I will for sure! :hell yeah: I should be taking the rotating assembly off sometime in the next couple weeks!!
 
^^ Thanks a lot for the help guys! I came to the conclusion that I am going to rip out the pistons, rods, and crank and get a stock 6 bolt short block from a friend. I am gonna send it to the machine shop and get it bored .20 over and get it all right then just throw my existing rotating assembly into it! (After inspecting it all) Im most likely gonna trash the short block since its a non turbo block anyways! :ohdamn: Such a waste of time and money but hey...No pain no gain!

If you bore it .020", you'll have to use .020" pistons and rings. You can't use std bore pistons/rings in an bored block. If it's a non turbo block, keep the block, the rods, and the pistons; the only things different from a turbo block are the pistons and the lack of oil squirters. I've built many a stout motor out of a N/T block.
 
If you bore it .020", you'll have to use .020" pistons and rings. You can't use std bore pistons/rings in an bored block. If it's a non turbo block, keep the block, the rods, and the pistons; the only things different from a turbo block are the pistons and the lack of oil squirters. I've built many a stout motor out of a N/T block.

Well my current N/T block is already bored .20 over! So I basically have the pistons, rods, and crank ready for installation! It basically comes down to trusting someone else's words over my own! I'd rather take the stock 6 bolt to the machine shop and know exactly what is done to the block! New bearings and new rings and I should have a brand new setup! That I also know is new! (peace of mind)
 
I hope the block you rob the pistons and rods from is also a 6 bolt.

Rod width differs between 6 bolt and 7 bolt.
 
I hope the block you rob the pistons and rods from is also a 6 bolt.

Rod width differs between 6 bolt and 7 bolt.

Oh yes it's a 6 bolt for sure!

Would you guys consider the old N/T block that I'm gonna have leftover to be junk??? Or can it be salvaged for some extra $$$? All of my clearances are in oem spec don't know about piston to wall clearance but everything checks out!
 
Depending on how bad the scoring is, it may hone .030, or have to be bored/honed .040

It dosnt look bad rnough to junk, strip it, put wheel bearing grease on the machined surfaces, place in a couple decent trash bags, and set it in the corner for when you need it again.
 
Thanks bogus!

So for my stock 6 bolt im gonna get it bored .20 over and honed! What else should I have done aside from cleaning!
 
Hhhh
 
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Wear in that area is normal since that is the part of the piston which rubs the cylinder walls, especially on a piston that doesn't have moly coated skirts like these:

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However, that much seems a bit excessive. Possibly too tight of a Piston-To-Wall clearance or not enough lubrication? Did you try to rotate all of the rings to make sure they aren't pinched? If it were me, I would get the block bored/honed first and see what size pistons you need. It's possible you won't be able to use those pistons again just because the cylinders will be too large for them. I personally wouldn't want to run a piston that looked like that.

I also wouldn't trash that NT block. They don't have oil squirters which means more oil to the bearings. Keep it in the corner for a rainy day project.
 
Hhhh
 
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Great thanks for the help! Well right now I have a completely stock spare 6 bolt block! I think that I am going to get it honed and use stock 1g pistons with my eagle rods! Would my eagle rods that are in my .20 over pistons be fine paired with stock 1g pistons??

The eagle rods won't be compatible with stock pistons because there are no grooves for the pin lock circlips. On stock rods the pin is pressed into the rod. With the eagle rods the pin is floating.
 
Hhhh
 
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Who did the machine work? The only reputable machine shop I know of near you is Rettig Bros. I hope it wasn't them, cause I use them for small projects.
 
Who did the machine work? The only reputable machine shop I know of near you is Rettig Bros. I hope it wasn't them, cause I use them for small projects.

I purchased the block already machined from the previous owner! I'm guessing that I got ripped off! Where exactly is Rettig bros located???
 
Hhhh
 
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I purchased the block already machined from the previous owner! I'm guessing that I got ripped off! Where exactly is Rettig bros located???

Modesto. They do 90% of their machine work in house and their turn around times are exceptional. Which is why I take the 1.5 hour drive out there when I need something small done at a very reasonable price, at an even better time frame. I prefer using Dave's Engine machining out here in Newark for my high performance stuff (its a trust thing). But for stock setups, cleaning, honing, they (Rettig Bros) can get it done.

You may want to take them your pistons and block to check piston to wall clearance. They may be able to clean everything up for you or at least inspect everything for a small fee and let you know what can and can't be used.

Be sure to keep the pistons matched or numbered to the bores so they can accurately measure things.

There's also a decent Mexican food spot me and my girl stop at when in Modesto called, La Huerta Vieja. :sneaky:
 
Hhhh
 
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OP, that doesn't look like scoring, its just some rub marks. My current more actually has quit a few deep scores in it. I put it back together as is, and it still runs great. It just has a little bit more blowby than I'd like. But it will get my thru untill next summer when I can build another motor.

If I were you Id be checking the ptw clearance. Making sure its at least .004" If its not, that was the issue.

I would also clean up the scoring on the pistons with some 320 grit sand paper then some 600. Finally, I'd take it to a shop and have it lightly honed to clean up the cylinders. Or honed to get the ptw clearance correct. Then put it back together with new rings.
 
OP, that doesn't look like scoring, its just some rub marks. My current more actually has quit a few deep scores in it. I put it back together as is, and it still runs great. It just has a little bit more blowby than I'd like. But it will get my thru untill next summer when I can build another motor.

If I were you Id be checking the ptw clearance. Making sure its at least .004" If its not, that was the issue.

I would also clean up the scoring on the pistons with some 320 grit sand paper then some 600. Finally, I'd take it to a shop and have it lightly honed to clean up the cylinders. Or honed to get the ptw clearance correct. Then put it back together with new rings.

That sounds like a great idea! Once I get some extra time and $ I'll take everything to the machine shop and get it all checked out, but for now I'm just gonna go with an oem 6 bolt shortblock!


Fyi If anyone has a set of 6 bolt oil squirters laying around I'd be glad to take them off your hands!
 
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