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Help cylinder wall pitting

42K views 12 replies 9 participants last post by  BogiesAnnex1 
#1 ·
Hey folks got a question for ya! I am building a 383 using an old 350 4 bolt block that has been laying around for years. The cylinder walls had some rust in them. I told the machine shop to check the block to see if it was good and if so bore it .030 over! Got the block back 2 weeks ago and I am ready to start putting this together. I was looking down each bore and admiring his work when I noticed mid way down the number 8 cylinder wall a slightly darkened area about the size of a silver dollar. I ran my fingers over it a few times and could feel a very very slight change in surface there. I got a high powered flood light to inspect it and it was almost not noticable but I could see a small amount of pitting there. Will this cause a problem or am I over re-acting? The machine shop didn't say anything about it when I picked it up.
 
#2 ·
It will probably be fine, however with all new internals you may want to find another block for peace of mind, personally ifit is barely able to be felt and you had to use a flood light to see it I'd use it.Oil on the cylinder walls does the sealing and will seal many things that look horible to the naked eye.
 
#4 ·
I would call the machine shop and talk to them about it. If all the cylinders cleaned but that one you may want to consider just sleeving that individual cylinder and boring it out to the others. Then you can still use the pistons (if you have already bought). What I don't like about this situation is that one the machine shop should have called you when they found it wasn't cleaning up during honing to decide what to do next (ie overbore more or sleeve) or they did not even notice, either of which isn't very good imo. Good luck with fixing that.

I personally dont like leaving things like that because it is always in the back of my mind when I am building and when it would be in the car.

Dennis
 
#5 ·
camaro freak said:
Hey folks got a question for ya! I am building a 383 using an old 350 4 bolt block that has been laying around for years. The cylinder walls had some rust in them. I told the machine shop to check the block to see if it was good and if so bore it .030 over! Got the block back 2 weeks ago and I am ready to start putting this together. I was looking down each bore and admiring his work when I noticed mid way down the number 8 cylinder wall a slightly darkened area about the size of a silver dollar. I ran my fingers over it a few times and could feel a very very slight change in surface there. I got a high powered flood light to inspect it and it was almost not noticable but I could see a small amount of pitting there. Will this cause a problem or am I over re-acting? The machine shop didn't say anything about it when I picked it up.
If the rings don't wipe over this area, it'll be OK. Unless this is a flaw in the casting as rust that has penetrated as deep as .015 inch is pretty serious rust, so you gotta know what this is.

In either bad case, the cylinder could be rescued with a thin wall sleeve.

Bogie
 
#6 ·
Great advice from all!!!

Ok, I just talked with the NAPA machine shop that is doing this. The machinist said that he noticed it but didn't think it would be a problem. He said that is why he didn't call me! He said that with break in it should be cleaned up by the rings.
 
#7 · (Edited)
camaro freak said:
He said that is why he didn't call me! He said that with break in it should be cleaned up by the rings.
But what if it doesn't and uses oil in that cylinder? Is he going to stand behind his statement and make it right.....I doubt it.

Vince
 
#8 ·
The older you get, the more you view things from a different perspective than those who have fewer experiences on this rock. This is one of those things I would call a "loose thread" that's hanging out there in the breeze. If you don't make this right before you bolt the motor together, it's gonna be on your mind the rest of the time you own this car. You may even get to the point that you subconsciencely don't want to drive the car at all. I don't mean to turn this into a drama, but I do have some experience with loose threads.
 
#10 ·
cylinder wall pitting

hi camaro freak, the first thing you should do is say goodby to your napa machinist. pitting where your rings travell is not good. a sleeve in your engine is not advisable as you would certainly distort the #6 bore. if you want to fix it right then sleeve it and rebore all cyls. to .040 or start over again with diff. block.
 
#11 ·
camaro freak said:
Ok, I just talked with the NAPA machine shop that is doing this. The machinist said that he noticed it but didn't think it would be a problem. He said that is why he didn't call me! He said that with break in it should be cleaned up by the rings.
I'm not there to see this and a picture probably won't do it justice, but I've never heard a machinist say it would be OK to run rings over such a site and it will heal. And I've been at this an awful long time.

Rust and or pits don't form a surface that one would want to run rings over. This will always be a place where the roughness of the pitting or softness of the rust will either wear on the rings like sand paper, will hold oil in the pits or softness that the rings can't wipe off which will then find it's way around the piston and into the combustion chamber, and or allow combustion gases to escape around the rings into the crankcase.

It is often considered acceptable to leave minor rust rust damage if it's below the zone of ring travel, especially if such damage isn't on a thrust face. But since the the thrust faces are perpendicular to the direction of crank rotation that puts a V8's pistons lowest point on the outside wall which is where water will accumulate if the engine is in it's normal upright position.

I really think, again not seeing, that the best thing to do is to install a thin wall sleeve that is finished to the piston size you're using. For a few dollars more this insures there's no problems, which are a lot more difficult and expensive to deal with after the engine's in service than before.

Bogie
 
#12 ·
Somebody brought this up before: where is the area of pitted material? If its low in the bore there's a good chance your rings won't make contact with the area at all and this is a non-issue entirely. If the rings do make contact with the area or you're not sure, I'd get that fixed in whatever way you think is prudent. I can't imagine ring break-in removing that much material from the bore to smooth out that surface. Even after break-in and several thousand miles you should still be able to find the cross-hatched pattern in the bores of a well-maintained motor. If the rings don't remove enough material to polish the bores clean of their honing/scoring there's no way they're going to wipe away pits! Rings were not designed to remove imperfections in the bore anyway, so the suggestion to let them do so is pretty irresponsible IMO.

K
 
#13 ·
techinspector1 said:
The older you get, the more you view things from a different perspective than those who have fewer experiences on this rock. This is one of those things I would call a "loose thread" that's hanging out there in the breeze. If you don't make this right before you bolt the motor together, it's gonna be on your mind the rest of the time you own this car. You may even get to the point that you subconsciencely don't want to drive the car at all. I don't mean to turn this into a drama, but I do have some experience with loose threads.
I like this; there's a great line in the 1953 movie Lindberg which is considered a quote. While the engine was being mated to the Spirit of St. Louis a mechanic dropped a wrench which hit a cylinder and nicked a cooling fin. Lindberg wanted the cylinder replaced fearing the nick would lead to a crack forming, the mechanic said he could, "dress the nick out with a file so you'd never know it was there." Lindberg retorted that he'd," always know it was there"...and... "didn't want that on his mind in mid Atlantic Ocean".

I have the same problem, life has enough uncertainties, I don't need to worry about things that I know are wrong and should have been fixed, there's enough to do worrying about what I don't know is wrong. It's the Bogie's Uncertainty Principle; but then when I was a young man I was a helicopter pilot and they are brooding introverts, anticipators of trouble because a helicopter does not naturally want to fly. I'm a firm believer in Murphy's Laws; "anything that can go wrong --- will go wrong".

Bogie
 
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