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Pitting in bore and deck
#1336906 Sun Dec 08 2019 03:14 PM
Joined: Jan 2009
Posts: 256
F
Shop Shark
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!

Re: Pitting in bore and deck
Ferndale53 #1336913 Sun Dec 08 2019 04:15 PM
Joined: Sep 2013
Posts: 1,038
M
Shop Shark
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

Last edited by moparguy; Sun Dec 08 2019 04:20 PM.

1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1951 Farmall Super A



Re: Pitting in bore and deck
Ferndale53 #1336934 Sun Dec 08 2019 06:14 PM
Joined: Mar 2010
Posts: 9,401
5
Master Gabster
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.

Re: Pitting in bore and deck
Ferndale53 #1336950 Sun Dec 08 2019 07:18 PM
Joined: Dec 2008
Posts: 1,471
P
Shop Shark
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.

Re: Pitting in bore and deck
Ferndale53 #1336954 Sun Dec 08 2019 07:30 PM
Joined: Dec 2008
Posts: 1,471
P
Shop Shark
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°).

Re: Pitting in bore and deck
panic #1336964 Sun Dec 08 2019 09:05 PM
Joined: May 2015
Posts: 2,638
Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums
Originally Posted by panic
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. frown
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.


Kevin
First car '29 Ford Special Coupe
#2 - '29 Ford pickup restored from the ground up.
Newest Project - 51 Chevy 3100 work truck. Photos [flickr.com]
Busting rust since the mid-60's
Re: Pitting in bore and deck
Ferndale53 #1336976 Sun Dec 08 2019 09:59 PM
Joined: Nov 2000
Posts: 1,961
F
Shop Shark
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.


Professional Novice
Re: Pitting in bore and deck
Frank50 #1336979 Sun Dec 08 2019 10:19 PM
Joined: Jan 2009
Posts: 256
F
Shop Shark
Thanks for the all the replys so far!

Originally Posted by panic
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.


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

Originally Posted by Frank50
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.


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

Re: Pitting in bore and deck
Ferndale53 #1336983 Sun Dec 08 2019 11:08 PM
Joined: Jan 2001
Posts: 5,007
P
Master Gabster

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.


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Re: Pitting in bore and deck
Ferndale53 #1336989 Sun Dec 08 2019 11:37 PM
Joined: Mar 2019
Posts: 957
G
Shop Shark
I think its junk.. Let me know when you throw it outside. I'll pick it up asap. thumbs_up

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