Cylinder ridge an inch down in the cylinder. What gives? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 04-30-2009, 06:17 PM
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Cylinder ridge an inch down in the cylinder. What gives?

I'm helping a friend of mine with a freshening up of a Dodge 400ci B-Block. After pulling the heads we found something kind of odd. We thought originally that the engine had never been in to, but found out differently when we saw .030 pistons in the bores. All the cylinders looked good except for the #7 cylinder. It appears that the cylinder ridge starts about an inch down in the hole. The ridge on all the cylinders is probably less than .005, but what would cause this problem. I don't think it's a broken ring, the walls look fine and the wear is all the way around the diameter of the cylinder bore. I guess it's possible that who ever rebuilt the engine forgot to put the compression ring on but the engine obviously ran for a while. It seems that a problem like this would have made the engines life rather short.

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Old 04-30-2009, 06:30 PM
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Maybe it was worn more than a .030" overbore would correct, but they had already bought the parts so they just made do with it? Or maybe a less than reputable shop was involved in the previous rebuild and slapped it together even though it wasn't right and should have been bored .040"? Same already in-hand parts scenario?
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Old 04-30-2009, 06:37 PM
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The ridge at the top of the bore is a smaller diameter than where the piston has worn the cylinder.
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Old 04-30-2009, 06:51 PM
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Quote:
Originally Posted by DaSouthWon
I'm helping a friend of mine with a freshening up of a Dodge 400ci B-Block. After pulling the heads we found something kind of odd. We thought originally that the engine had never been in to, but found out differently when we saw .030 pistons in the bores. All the cylinders looked good except for the #7 cylinder. It appears that the cylinder ridge starts about an inch down in the hole. The ridge on all the cylinders is probably less than .005, but what would cause this problem. I don't think it's a broken ring, the walls look fine and the wear is all the way around the diameter of the cylinder bore. I guess it's possible that who ever rebuilt the engine forgot to put the compression ring on but the engine obviously ran for a while. It seems that a problem like this would have made the engines life rather short.
With a Chrysler product that doesn't necessarily mean anything, they haven't been able to make a block with standard bores in 50 years. Check the crank for journal size another place to find "fixes". If their not all a different size consider yourselves lucky.

Look at the pistons, many Chrysler engines use a very high crown with the rings down around the pin. This results in the ridge being much lower in the bore than expected.

Bogie
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Old 04-30-2009, 08:29 PM
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I would think the machining done when it was rebuilt would have taken care of any bore variations. After thinking on it a while I think what probably happened is that when the engine was taken out of use from what ever it's former life was the intake valve just happened to be in the open position and some funk got down in there. It doesn't appear to be corrosion but it's pretty much impossible for it to be anything else. Mechanically I cant think of anything that would cause it, especially in an engine that ran. I figure at an inch from top dead center one valve or the other should be opening or closing depending on stroke.
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Old 04-30-2009, 09:44 PM
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ring installed up side down / too little end gap, compression leaking by compression ring and creating excessive pressure behind second ring (due to small gap) causing wear pattern.
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Old 04-30-2009, 11:22 PM
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Cracked top ring.
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Old 04-30-2009, 11:29 PM
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It appears that the ridge is below where even the oil ring would be when the cylinder is at tdc. It literally extends a good inch down from the top of the bore. The pistons sit .100 below the deck. I didn't want to pull this bottem end apart but I may pull that one piston out to see whats up.
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Old 05-01-2009, 04:39 AM
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ridge

Better look real close. My guess, with out seeing any pictures is that the block is split, and it pushed the cylinder out at that location..

I could be of more help with a picture though..


Keith
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Old 05-02-2009, 12:07 AM
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Eww yuck, that seems to be the only thing that really makes sense. I'll try to get a pic tomorrow and get a better look for cracks.
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Old 05-02-2009, 05:46 AM
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I`ve never been into a dodge engine but I`ve heard stories. I have seen some "fixed" small block chevy`s. A friend of mine had a 305 in his 84 pick up, we knew the engine had been gone through but didn`t know to what extent. When it spun a rod bearing we stripped it down and found many of the crank journals a different size. My friend was curious on why it was assembled like this so he called up the original owner. The machinist built the engine the first go round and was told to build it "cheap as possible" and this was the result. As for the wear pattern on your engine I`m interested to see what you find once you get that far.
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