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ezobens 03-19-2006 02:06 PM

400 SBC Steam Hole Crack
This is turning out to be the rebuild from hell-
I am getting ready to assemble my 400 SBC and was inspecting the block after it came back from the shop for a .040 overbore and some mild decking. I was a little ticked to find that I have a hairline crack in the upper steam hole between cyls 3 and 5. This hairline crack runs from the upper steam hole to the bolt hole directly above it (about 1/8"-3/16" long). I cannot tell how far down the holes this crack actually goes.
First I'm a little frustrated at the shop not noticing or notifying me of the crack and second, where do I go from here?
The block otherwise looks to be almost perfect- The bores, crank and rods were all standard size when I bought the motor and it supposedly ran before being pulled from the seller's truck. I did notice that one of the previous owners did have the heads off at one time- And while it had the correct 400 heads, the clown used standard SBC head gaskets that didn't have the steam holes so the center cylinders on both side looked like they ran hotter than the others. There are NO cracks in the bore area and I can't see any other cracks in the steam holes other than this one on the left bank.
What are my options?
I would be most upset if I had to junk this block just for this- Can I have the shop weld the hole/crack and re-drill the hole and the block?
Any advice would be greatly appreciated!

coldknock 03-19-2006 03:20 PM

Run the snot out of it. A crack in that position won't hurt a thing, even if it went all the way through to the water jacket.

Remember to use thread sealer on the head bolts.


machine shop tom 03-19-2006 03:29 PM

A LOT of guys are running their 400s with those cracks and don't even know it. As was said, use a sealer on the bolt threads and don't worry about it.


ezobens 03-19-2006 05:50 PM

Should I still drill holes in my heads?
Whew.. That is a relief. I was really worried that this thing was trash.
So this crack won't hurt the ability of this one head bolt to torque down or anything, will it?
Also, since I am running L-98 aluminum heads with 10.5:1 compression, I was planning to only drill the bottom (exhaust side) steam holes in these heads. In light of this, will this still be OK or should I have the intake side holes drilled as well?
Elm 03-19-2006 08:27 PM

If you don't trust ths "Seal the snot out of it" idea.

I have been repairing these cracks by drilling and tapping a cast iron "stitch" plug into the steam hole. Cut off flush with deck. Then drilling a slightly smaller steam hole in it. This completely seals the crack and leaves NO sealing problems

ezobens 03-20-2006 07:28 AM

Stitch Plug?
I see where drilling and tapping this plug would seal the steam hole area itself but I still don't see how that would actually 'fix' the crack going to the head bolt hole? Seems that some welding would be required in any case?
Am I missing something?

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