I have a Pontiac 400 engine block that I was going to use in my '51 Pontiac Chieftain. I've now decided maybe I'll save the original straight 8. Anyway, I have someone interested in buying the 400 block for what I have in it, $200. I was just out in the shop and noticed it has a pretty deep scratch n one of the walls. It looks as if something in my shop damaged it. The block had been recently machined before I got it. The block had been bored to .030 over. What can be done? I can try to hone it, but I have a feeling the scratch is too deep. I'm guessing it will need to be bored more? Thanks, Ed
Not enough info....is the scratch in the top half of the bore, where the rings travel? how deep is it? a couple thousandths? 10 thousandths? more? what direction is it? Can you try to take a picture?
I would not worry about that. It's like a pit, pretty far down in the bore. I'd worry more about the vertical scratches that didn't get honed out.
It wasn't freshly bored. I got it for free (I had to pay shipping) from a HAMB member who used it in his '67 GTO until he got a code matching block. He said he ran it a couple of hundred miles after he finished the restore. Ed
I know this will turn into a ******* match, but the VERTICLE grooves you DON'T have to worry about. The only negative aspect there would be compression or cylinder pressure will leak past the area in question. You will see some very minor loss of compression and some minor cylinder leak down, but the rings will go up and down the grooves with no problem all day long. What you DO have to worry about is a blemmish DIAGONALLY in the cylinder bore. This is what will catch the rings and or piston during it's travel. Now if your still there, take something like a steel dental pick or a O-ring pick and dig into the crevace. You might break right through into water and that's IS what you want to find out or not. The next stage would be to determine just how deep the blemmish is and a good machinist and you get together and possibly sleve that cylinder, or bore them all and re-hone. All the best.
BTW, I don't care who you are, what I said is fact, provided that in the verticle scratches they are less than the surface of the cylinder wall, and not raised up into the cylinder inside diameter at all. Meaning the scratch is not raised. If there is some question, sometimes as little as a dingle ball hone can knock down any raised metal and also provide a quick and light cross hatch.
I'd give it a light honing and call it good. Get a 2nd opinion if you're worried about it, it doesn't look that deep in the picture and seems to be offset from the centerline of the bore (not square to the crank). Bob
One of the things that bothered me is that the scratch is slightly raised, and it is on a diagonal. Something must have fallen down on the pallet that it was sitting on in my shop at some time. Ed
Just make sure that "Scratch" you call it is not a broken chunk in the cyl wall. Looks like something hit it pretty hard. Lippy
You could get most of the raised portion of the ding out with crocus cloth before you hone it. Splash some layout dye (or a big sharpie) on the surface to check the progress. Bob
I'm thinking I will tell the guy the situation and if he still wants it that's great. If he doesn't, I might just drop it off at the machine shop and get their input. Maybe I'll come across a different project to use it on. Ed
You guys really are a pool of knowledge and very helpful. I truely appreciate all the input. I wish I knew more about machining and engine building. Thanks, Ed
"get a second opinion" my god on here you would be lucky to only get a "second" opinion. A lot of good answers here but the feel test is the one.
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