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Author Topic:   Broken pistons
intimidtr3
Member
posted January 19, 2003 07:52 PM
I have a 400 sbc in my pick up and as I was driving down the road it lost power and wouldn't even pull itself.I towed it home and pulled the plugs,5 electrodes were missing 2 were bent and 1 was still good.I put new plugs in it and i made some noise so I shut it off and pulled it out(it never did not start and run).I pulled the heads and the # 5,7,4,and 6 cyl. had broken pistons(about an inch or a little more broke off)and you could see the rings.the top of 7 pistons are all nicked up but not broken.I found 2 little pieces of metal but thats it.I had an edlebrock on it and it wouldn't run so I put on a brand new 500 Holley(4412) and a new distributor.It seemed to run fine then all of a sudden it started acting up.I am thinking that maybe my carb wasn't adjusted right or maybe I got the wrong plugs at parts store,I don't really know.I would greatly appreciate any input on what you all think could have gone wrong,Oh yeah the motor has less than 5,000 miles on it and 350 heads.Thank You,J


John Bottoms
Member
posted January 19, 2003 08:20 PM
Your problem is probably detonation. This would be caused by advancing the timing to much. We had the same thing happen to our race engine. Did yours run hot like ours did? How much total timing did you have in it?


intimidtr3
Member
posted January 19, 2003 08:31 PM
I just pulled timing cover off and had 1 inch of play in the chain on both sides and can move the cam wothout turning anything else. Could this be the problem with it advancing itself too much? And yes it got hot.


John Bottoms
Member
posted January 19, 2003 09:11 PM
I was just looking back over your original question and are you sure the 350 heads have the steam holes necessary to be run on a 400? Also, of course you shouldn't be able to move the cam without moving other components. With the tops of the pistons eat off to the rings, it does sound like detonation.


outlawstock17
Member
posted January 19, 2003 09:17 PM
no intimidtr3, the timing chain position only controls mechanical timing. john bottoms was referring to electrical timing. it sounds to me like you had too much advance, possibly combined with a lean condition caused by the new carburetor. if the reach on the spark plug was too long, you would've had a problem as soon as you fired it up. i'd definitely replace the timing chain though.



intimidtr3
Member
posted January 19, 2003 09:30 PM
John Bottoms - What do you mean by steam holes? I didn't build the engine, but checked casting #s and they are definately 350 heads.
Thanks


WillieWinn
Member
posted January 19, 2003 10:01 PM
My mistake the web site I put my head #s in said they were 350 heads,I found 2 more that said they r 400 heads.My bad.


powercar821111
Member
posted January 20, 2003 11:21 AM
As the cam advances, so does the distributor timing........detonation.


Flatlander
Member
posted January 20, 2003 09:08 PM
It had a Holley 500(4412) on it at the time.No water in cylinders when I pulled the heads off.


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