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Old 05-21-2007, 02:39 PM
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350 heads on 400 eng. by mistake

I may have put 350 heads on 400 block, seem to run ok, what will steam hole in block do, thank you Ray

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Old 05-21-2007, 03:39 PM
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If you did install 350 heads on a 400, and did not have the steam holes drilled in the heads it will run hot due to hot spots that develop due to the siamesed cylinders in a 400 block.
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Old 05-21-2007, 04:35 PM
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i've got a 400 ... ditto on the above... but

What all have you done to yours? I am planning a rebuild and would like to hear what other 400 owners have done.
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Old 05-21-2007, 05:37 PM
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You need to pull the heads.
The steam holes let the water circulate around the clyinders. Without them air pockets form and they overheat.

You can drill the steam holes yourself, but you have to pull the heads.

I have a 434, .030 over, 4" stroke, splayed caps, forged crank, about .5" lift
( shoulda gone bigger) AFR 210 heads, but it pushed my '69 Vette into the 11.90's at 118mph
all motor, crappy tune.

500 ft/lbs sure is fun on the street, as is 400 ft/lbs from <2400rpm to 6000rpm...
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Old 05-21-2007, 07:21 PM
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Quote:
Originally Posted by retired 56
I may have put 350 heads on 400 block, seem to run ok, what will steam hole in block do, thank you Ray
The steam holes let coolant flow from the top of the cylinder where they are siamesed into the head. This prevents local overheating at this point from forming a steam pocket under the cylinder deck. The heads's fine but the bores aren't. This is not the kind of overheating that will show on the temp gauge, it's strictly local and causes the cylinders to distort which might break the gasket seal.

If you remove the heads and lay a 400 gasket on them, you'll see 6 needed holes between the inboard cylinders. Mark and center punch where these line up. Using a sharp 1/8th or 3/16s bit; drill the exhaust side straight into the water jacket. On the valley or intake side drill at a 30 degree angle toward the exhaust side into the water jacket. Make sure your center punch is deep enough to keep the bit from skating off across the machined surface. Lightly dress the hole to make sure there's no raised edge or burr that would interfere with the gasket seal.

Bogie
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Old 05-22-2007, 01:45 AM
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http://www.gregsengine.com/350to400.htm
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Old 05-22-2007, 07:52 AM
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pull the heads soon .. the block will warp slash crack if you run it to long like that...

as for 500 ft/lbs of torque..5.7 rod stock crank good roller hydrolic cam... haha yah and gas milage to boot in a 3/4 ton truck...
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Old 05-22-2007, 01:19 PM
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Had the same problem on mine. I just got a .040 over 400 from a friend of mine, and the head gaskets were F##ked. It has a set of stock 350 heads on it, with no steam holes. I drilled them out, new gaskets, fired it up on the cart(74 Nova front clip) and she is solid.
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