Mr Riviera Posted July 13, 2008 Share Posted July 13, 2008 I pulled the heads today on a 425 eng. that has been sitting for years . I found that # 3 and # 4 pistons had jagged holes right in the center of the pistons . No visable damage to the cylinder walls , no pieces on top of the pistons and no damage to the pistons around the broken area . The broken pieces must have gone down but the eng. turns over by hand very well. Any thoughts on the cause of something like this ? Will pull the pan when I get back from Flint. Thanks, Link to comment Share on other sites More sharing options...
Pete Phillips Posted July 13, 2008 Share Posted July 13, 2008 If the engine was/is stuck, perhaps someone has removed the heads before and tried pounding or hammering on the stuck pistons?Other causes:--broken connecting rods--foreign objects being ingested through the carburetor (like maybe a loose bolt) while the engine was running--very bad pre-ignition? I've heard of bad pre-ignition blowing a hole in pistons, but have never seen it.Pete Phillips, BCA #7338Sherman, TX1949 Super Estate Wagon1950 Roadmaster 76-R1963 Wildcat conv. 425 4-spd. Link to comment Share on other sites More sharing options...
The Old Guy Posted July 13, 2008 Share Posted July 13, 2008 Pete hit it on the nose. It is pre ignition. I did the same thing to a 455 by running too much timing and running down the drag strip. Link to comment Share on other sites More sharing options...
Bhigdog Posted July 13, 2008 Share Posted July 13, 2008 The Older nail heads required that the ignition wires be routed in a certain order to prevent cross firing. Same effect as preignition just a different cause.......Bob Link to comment Share on other sites More sharing options...
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