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Truckedup 11-14-2011 02:56 PM

Rust pit on cylinder wall
I bought an engine off of Craig's's a vintage GMC inline 6 with speed equipment,the Ross forged pistons are very nice.It was quite dirty from sitting uncovered in a heated garage.It was a great deal,money wise...............
After cleaning the block I noticed a rust pit about an inch and a half down in one of the cylinders.The cylinders look newly finished and a bore gauge confirms this.Probably was there after honing....It's about 7/16 of an inch around and by sticking a ring in the cylinder I estimate the depth at no more than .002. The cylinders have the proper clearance for these pistons,.0045. Trying to hone the cylinder clean will result in a very sloppy fit, I called Ross to verify the clearance.
I showed the block to the local machine shop I am friendly with.He looked for awhile and said to run it.He says it might use a touch of oil but cylinder sealing should be reasonable.
Boring oversize will make this set of pistons useless,they cost about 700 bucks with the rings.Finding another block is possible of course.But then after boring the block and all that......

ap72 11-14-2011 03:11 PM

Sleeve it. Cheapest way out.

WDCreech 11-14-2011 03:24 PM

I have a friend that has a Pontiac convertable that he put a used 455 in. One cylinder had a pit about the size of a fingernail clipping. He started using one of those "miracle", off the shelf, oil additaves with each oil change and it dropped his oil consumption to almost nothing. I'm not sure which product it was, but the name Restore comes to mind. Hope this helps!

Gringo 11-14-2011 04:29 PM

I'd just run it. Oil is cheap. Some of the motors that ran good would scare you to death when opened up. I think a lot of this stuff is overkill. I think back to some of the things we use to get by with and got by fine. Such as dumping scouring power in a six cyl. chev to scuff cyls. It worked. had better compression and used less oil. Fileing rod caps to tighten up loose rods. Dumping pepper in flatheads with cracked blocks. and the list goes on.

cobalt327 11-14-2011 09:11 PM

Just the one cylinder? Sleeve it.

66GMC 11-14-2011 09:39 PM

I would think that "what to do about it" depends on "what you're going to do WITH it"

If it's a parade car, or a trailer queen, etc ... I'd just run it.
I've heard stories of model A's with one wooden piston. :D

(Perhaps that was a "we used to walk 5 miles to school, through 3 feet of snow, uphill both ways" style of yarn.) :D

Truckedup 11-15-2011 03:20 AM

No,it's not a parade engine what ever that is.. The block is now at the maximum safe over bore .I talked to several shops about a sleeve and they all hesitated due to the bore size leaving the sleeve thin and all that.
I have two choices,get another block...Or assemble it as is and see what happens and for sure I'll know , :D

sbchevfreak 11-15-2011 07:28 AM


Or assemble it as is and see what happens and for sure I'll know ,
Do it. Make sure the edges are not going to grab the rings (light scuff with some fine emery paper, rag underneath to catch any debris), and give 'er!

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