While doing a final cleaning prior to assembling my '79, 225 block, I found the small coolant passage adjacent to #5 is plugged. I thought it was the usual calcified, heat-hardened gunk and tried to dig it out, but it's plugged with metal, and must have happened during the casting process.

I have no idea how deep it extends, but it doesn't punch out easily. I suppose I can drill to see if I can reach the water jacket, but that might be a fruitless effort.

I can't recall ever seeing this, but I honestly can't recall if I even checked them all in the past.

Is this an unusual problem? Opinions about how serious this could be?

Are we talking about the tapped block drain hole on the passenger side of the block or one of the holes on the top deck surface?
DD

One of the six small ones on the block deck.

If it's the one I'm thinking of that's one under an exhaust valve and should be drilled through.

_________________
Joshua

Photos would help positive ID.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

The blockage is 1" down.
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what you describe does indeed sound to be the result of a cracked water jacket core. Does the blockage run up and down?
Foundry processs are much improved from the days of the slant six,, back then, generally speaking if an internal passage was 85% open, it was acceptable,although blockage from the top down is more of an issue than blockage from the bottom up.
If the motor had miles on it,, the bore / piston was not scuffed, then it has been running that way and has not hurt it yet, I would bet it would still function the same way after a rebuild.
many modern engines have the bores siamesed,,for rigidity.

It sounds like one of the 6 "steam holes" that run aloug the driver's side of the top deck. These holes are really exhaust port cooling passages, because they are placed right under each exhaust port and allow a small amount of colder block coolent to "short-cut" up into the head, right under each exhaust port.



I routeenly drill these holes out, to remove rust scale and to take them a bit oversize. (I match the hole size in the head gasket)
You should drill out your plugged hole so it is clear for coolent to pass thru.
DD

It was a high-miles engine, but there was no damage beyond normal wear. It's going into a stock daily driver, so I guess I'm not terribly worried, but I still think I'll drill it out.

Thanks for the help, guys.

if the blockage is a vertical "vein" inside the water jacket, a tool that was used to work it away was a length of round piano wire steel, 1/16 to an 1/8 inch in diameter. bend it in a L shape with the short end of the L about an inch and a half long, long end maybe 8 inches long, mount the long end in a wood handel, sharpen the upper edge of the short end, fish the short end into the water jacket and work on the vein, starting that the bottom of the vein and pulling up. If what you are seeing is truly a vein, (core sand expansion defect) it can be removed this way. Veins are typically no more than .020 thick. If the blockage you are seeing is thick, like .125 + it was caused by an broken core.

In case anyone was curious...I had to drill nearly 1/2" deep to remove the blockage. The material removed by the drill bit was mostly metal with grains of sand stuck in it.

Sintered core sand... a section of the sand core that was not packed tight prior to the core hardening. The porous sand allows some metal to penetrate and leaves the semi sand / semi metal feature that you found.
This is a pretty common defect found on sand castings.
DD