Cracked pistons?
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Cracked pistons?
I pulled what I believe to be the original motor from my 94 f-250 turbo, due to connecting rod failure. Pulled the heads off and found most of the pistons where cracked in the center. They where all stamped with an A but one. It was stamped with a B. So I installed a used engine from a 92 non-turbo. Ran it. Runs very good but leaked oil from the head gaskets. So I am in the process of removing the heads and just as I remove the driver side head find #2 piston with a small crack in the center of the dish.. Now what to do? Has anyone seen this before. Why does it happen (advanced IP timing, high EGT's) and what is a economic course of action? Any help is appreciated.
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From: Kent WA
Originally Posted by polish
I pulled what I believe to be the original motor from my 94 f-250 turbo, due to connecting rod failure. Pulled the heads off and found most of the pistons where cracked in the center. They where all stamped with an A but one. It was stamped with a B. So I installed a used engine from a 92 non-turbo. Ran it. Runs very good but leaked oil from the head gaskets. So I am in the process of removing the heads and just as I remove the driver side head find #2 piston with a small crack in the center of the dish.. Now what to do? Has anyone seen this before. Why does it happen (advanced IP timing, high EGT's) and what is a economic course of action? Any help is appreciated.
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
Strange as it may seem, the factory used different pistons in the 7.3 blocks, A thru D.
The piston and cylinder (under the cam if I remember right) should be stamped with corresponding letters. When replacing pistons you may use an S piston in any of the cylinders.
The piston and cylinder (under the cam if I remember right) should be stamped with corresponding letters. When replacing pistons you may use an S piston in any of the cylinders.
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Should I replace all pistons or can I get away with replacing only the cracked ones? How common is this? And does the cracked piston pose any real problems. I never noticed any when I was driving it?
Posting Guru
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From: Northeastern Pa - USA
from my past experiences the pistons crack from TOO MUCH HEAT or bad injectors spraying improperly. The crack in the piston may cause further problems when it reaches edges of the piston. If you have it apart may just as well clean all the pistons and see if any of the others are cracked. In the larger engines we only replaced the broken pistons or those with visible cracks.
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Dave, when you had all those problems with those 7.3....did they have cracked pistons? Is this a common problem with IDI's? Just curious.
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Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
Most of my problems were block and head cracks, but the last engine that blew did have a crack that went from one side of the piston to the other.
The piston rotated in the bore, so it was not attached to the rod anymore.
Since the engine was under warranty I did not get to remove the oil pan and see what actually broke, the fact it did not go up and down and was rotated in the bore was enough for them to replace it.
Every head I pulled on the reman 7.3 engines had cracks in them near the precups.
I like my 6.9 engine just fine.
Those 7.3 engines were not fast enough anyway.
The piston rotated in the bore, so it was not attached to the rod anymore.
Since the engine was under warranty I did not get to remove the oil pan and see what actually broke, the fact it did not go up and down and was rotated in the bore was enough for them to replace it.
Every head I pulled on the reman 7.3 engines had cracks in them near the precups.
I like my 6.9 engine just fine.
Those 7.3 engines were not fast enough anyway.
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Post Fiend
Joined: Nov 2004
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From: Manitoba
Remember on the 7.3 the 2 back pistons are larger........ #s 7 and 8.....
Many newbie owners do not know how to remove the IDI heads and can in fact crack them............ Always remove the head bolts in reverse order of the installation, ie 17 down to 1 in a rotational pattern, loosen only about 1/8th of a turn per per bolt, per pattern (round). It should only take about 3 times around, do not use air ratchets........use a long bar and socket for control.
Many newbie owners do not know how to remove the IDI heads and can in fact crack them............ Always remove the head bolts in reverse order of the installation, ie 17 down to 1 in a rotational pattern, loosen only about 1/8th of a turn per per bolt, per pattern (round). It should only take about 3 times around, do not use air ratchets........use a long bar and socket for control.
Last edited by PLC7.3; Nov 17, 2006 at 11:30 PM.
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
After I tried buying a 7.3 turbo upgrade reman engine and blew three up in 28,000 miles
I built a 6.9 turbo myself.
Those 7.3 turbo motors had about half the power I have now.
You can use an S piston in any cylinder.
I built a 6.9 turbo myself.
Those 7.3 turbo motors had about half the power I have now.
You can use an S piston in any cylinder.
