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Al Newman 07-19-2014 08:21 AM

5.0 engine mystery
Tore into a 1995 5.0 today and found all four pistons on the driver's side with cracked ring lands. No lands were cracked on the passenger's side. Motor had very little use, as cylinder wear was not measureable - no top ridge, no measureable cylinder wear in lower cylinder wall. Any ideas as to how this could happen. Compression check prior to disassembly was 150 on passenger side and 60 on driver side.

barnett468 07-19-2014 08:17 PM


nope, makes no sense unless they were running nitrous on that side of the engine only or milled the heack out of that cylinder head only or had the ign timing advanced a lot on that side only.

67mustang302 07-19-2014 09:31 PM

Or the ring gap was all too tight on that side. Or the cooling system was clogged on that side?

It is pretty odd, and whatever the cause was, it's likely it came from a human source at one point or another.

bop11 07-21-2014 09:47 AM

When was the engine rebuilt? Wrong size pistons or rings as '67mustang302' said.
Are the top rings black? If so could be excess fuel from a dripping injector on that side causing detonation of unburned fuel in the land space. The other side with proper mixture did not experience this.

Al Newman 07-21-2014 02:03 PM

Thanks for all the ideas. The engine has never been rebuilt. With fuel disribution from either fuel injection or carburetion, I can't see how only one side of the motor was experiencing an issue. Same with nitrous. Clogged cooling system should have shown up on plugs or discoloration of the exhaust manifold on that side, none of which provided a clue. The engine has so few miles on it that there is absolutely no top ring ridge whatsoever and the bore is standard. Must be just one heck of coincidence. Hard to imagine. That's why I posed the question to see if anyone else has encountered such a thing.

bop11 07-22-2014 12:28 PM

try go to post by Bill Jones

Al Newman 07-22-2014 06:08 PM

Thanks, BOP. Very informative chat. I think after looking at everything that most likely the intake on this motor was loose on the driver's side, thus allowing air to leak into the fuel flow and create a lean condition on just one side of the motor. Any other cause of a lean condition, given the motor had 1991 fuel management, would have not been so selective as to detonate only one side of the motor. I appreciate all input. This is how us "unwashed hobbyists" can learn about our passion.

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