I'm tearing down a new to me block w/117k miles on it, and there is
significant cross hatching visible and no ridge at the tops of the
cylinders. (It does appear that one has been removed though) Am I correct in
reading this as a ring job done in the not too distant past? I can't find
any numbers as to how long the cross hatch pattern from honing lasts, any
info would be greatly appreciated. There is some vertical lining on the thrust side of the cylinder walls, but the cross hatching is still clearly visible. I would suspect that any marks from the
factory would be long gone at this point, correct?

Thanks in advance!

 

is it a consitant crosshatch? and in all the cylinders? you might have caught a break then. How much, if any, carbon deposits on the pistons?

 

Might be a sign, might not be. In the book "Rebuilding the GM 60 degree v6", Tom Currao wrote that it's not uncommon to still find the factory crosshatch in the cylinders. You might just have a motor that was taken very good care of! But if there's evidence of a removed ridge at the top of the bores, it does suggest that something was done. Do you have a telescoping gauge, or any way to verify the bore diameter?

 

Look for heaver crosshatch marks on the bottem of the bore visually compare them with the upper marks. If there similar then its possible its has been rebuilt rescently. Do check the bore for stock size though. 4 of the 6 2.8's I rebuilt dident need to be bored and were all in good shape around 150K. Full sythentic oil can keep the engine in good shape also giving the results you see. Sounds like you got lucky either way, minimal machine shop cost.

 

The stock engine number 1 cylinder will have a considerable ridge on it if it hasn't been machined before. The coolant passage enters there and causes that cylinder to be a little tighter than the others. Also, if it had been done, you need to check the cylinder bore and verify the size. I believe tha the stock diameter is 3.504" on our engines. I just rebuilt mine and would be glad to answer any questions that you have!

dale

 

No, there is no ridge on the #1 cylinder. Nice and level, used a machinist's rule down the bore, couldn't slip a feeler gauge under it. Unfortunately I don't have a pin gauge, just a digital caliper so I cannot measure mid-bore. Top bores are all factory though, something I found a little odd itself. I haven't had a chance to open the bottom end yet, hopefully this weekend. It'll be interesting to see what it looks like. So far this motor is looking a lot better than my 2.8 did ~100k miles after rebuild.

Does anyone know a good place online to buy rings? Can't seem to find a decent price locally. I'm thinking that if I can afford them, I might as well hone and re-ring just to be on the safe side.

p.s.: Should have mentioned in my first post, this is a 3.4 from a 4th gen. Didn't find any info about different cylinder wall composition for them, but maybe...?