The Stovebolt Site Forums The Shop Area Engine Shop Pitting in bore and deck

I just picked up a rebuilt 261 that had been sitting for many years (bored .030 over and never run). It was sealed up pretty well and stored inside so I was hoping it wouldn't have any issues but no luck.

Overall picture: https://i.imgur.com/MBXTfI2.jpg

I pulled the head off and found some rust on the deck of the block as well as in the #2 cylinder.

Here is a picture of the rust on the deck. It is just limited to the combustion chamber area and doesn't impact any areas sealed by the head gasket.

Deck pic #1: https://i.imgur.com/Yt1SdXe.jpg
#2: https://i.imgur.com/6HLnA1s.jpg
#3: https://i.imgur.com/HyPQJNh.jpg
#4: https://i.imgur.com/Emzg2WB.jpg

Here are some pictures of the #2 cylinder. All the rest are perfect but of course this one had to have some rust. I can spin the engine over and it doesn't seem to drag or bind when it reaches that area

Bore pic #1: https://i.imgur.com/qo0ZRk8.jpg
Bore pic #2: https://i.imgur.com/AnvEeQb.jpg

My gut tells me to at the minimum have the #2 cylinder honed if not sleeved. I'm assuming / hoping that since the rust on the deck doesn't impact that head gasket that it shouldn't be an issue. But i'm no expect so if anyone has any advice i'm all ears.

Thanks!

More "expert" opinions will follow. And with the caveat that I really can't tell how deep the corrosion is, I'd first of all take steel wool or some 320-400 grit sand paper (after stuffing a clean shop rag in the cylinder below the rust) and with a little spray lube work on the rust to see just how deep it is. If as superficial as it appears, next step would be to reassembly the engine, install and enjoy. If it's not just surface rust then I'd hone it till it was near perfect. Then move on with a good cleaning and reassemble, etc, etc.


Good Luck,
RonR

If there are pits which catch your finger nail, you would be best advised to have that cylinder bored until the pits disappear. Honing until the pits disappear would take forever and not give you a true bore. You will need a new oversize piston and oversize ring set for that piston.
The location of that spot is worst case scenario. The big boom goes on right there.
If you can't catch your finger on that spot, I would do nothing but put it back together, break in the cam, and drive it to break in the rings.

Can't comment on the deck.
The bore is not that bad:
1. the area above the top ring @ TDC is completely harmless in terms of seal
2. the large spot below that is in the ring path, but so high up that no serious gas pressure is present, and the rod is so close to vertical that the crank has no "leverage". Give me the distance in inches from the deck to the bottom of the spot and I'll give you the crank position in degrees.

Clean off what you can and run it.

Note: you may actually see this on the 'net: "To find the crankshaft rotational position from the piston's location in the bore, divide the stroke in inches by 180°. This gives you the stroke per degree. Example: 4.00" stroke ÷ 180 = .0222" per degree. Divide the measured piston position down from TDC by .0222" to get the crank angle. In this case, the piston is 1.13" down, so the rotation is 51°.

This is always wrong at every point (except 0° and 180°).

Yep, wrong.
But with more math, the crank angle can be calculated. But the math makes my old brain hurt.
It's more complicated than sticking a horizontal cylindrical fuel tank to figure out how much fuel is in it. I have a cheat sheet for that, though.

Maybe it’s the picture or just me. I don’t see any hatch lines from the hone as I would expect from a fresh rebuild.

Thanks for the all the replys so far!


The bottom of that spot is right around .8" down from the deck.


Its just the mediocre pictures, there is definitely cross-hatching in all the bores.

The pitting on the top is of no concern, as long as it is not in the sealing ring area of the head gasket.

The pitting on the cylinder walls are fine, as long as you lightly remove any high spots.

I think its junk.. Let me know when you throw it outside. I'll pick it up asap.

W/r/t the crank angle can be calculated
I wrote an .xls to do this, it's just trig not rocket science.

.8" (20.3% of stroke) down from TDC is just under 48° (26.7% of stroke). There is actually combustion pressure at this point, but how much is lost...? IDK.

I'm closer. Call me. I'll be right there, but I won't even charge you what Glenn will charge you to tow it away.

Hahaha. RUN IT! Wouldn’t even think about it. My last motor in my racecar had water sit in it for some time at the junkyard. Was a v8 so it hand 2-3 eyebrow like rust rings in some cylinders. Not so much just light rust but more like that part of the cylinder was eroded away and you could probably see past the rings if you hit it with a flashlight from the bottom. Ran like a champ and made great power and never so much as even a puff of smoke. I beat it like it owed me $$$$ for at least 2 years. Most people would have thrown that block away. Its still sitting in my garage wrapped in plastic waiting to get called back to duty.

Scotch Brite, WD40 and go to town on removing what you can. Assemble and run it, you will never know it was there. Its just the rust deep in the cast iron working its way back out. I would bet it was real rusty before machining it. I recently worked on a set of heads that were rusty, after sand blasting and jet washing, they looked like new, for about three days. Then the rust came back just as your block did. I could keep polishing it off, but it always came back. They are on an engine and running great.

I wouldn't bother me a bit to run it, even if the pits don't clean up 100%.