If rings were bad ina cylinder how much of a pressure drop would u see on a leak down test gauge ? (in percent) ?

I went ahead and squirted oil in my dead cylinder today and compression stayed at 150 PSI like the rest of the cylinders, wheareas it would be at 120 PSI w/out the oil.

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92 Z28 L98 350
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Ported and polished heads, ported stock TPI base, ported plenum, Comp Cams XR270HR-10 cam (lift .495/.502 duration 218/224 lobe separation 110), Edelbrock TES headers, LT4 valve springs, Crane AFPR, Flowmaster catback with LT1 style tips, MSD coil & wires...

"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)

 

btt

 

A difference of less than 10% is considered acceptable. Differences of greater than 10% start to indicate problems differences 15% to 20% shows big problems. The engine may still be driveable but will not have top proformance or economy.

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2E,87 Formula 350, 4 other Camaro's & 3 Firebirds to fix, Drive, or sell.

 

That would kind of depend on exactly how bad they were... you might get anything from a slight leak to no ability to hold pressure at all.

It sounds to me like you may have a ring problem, maybe just stuck ones. You might want to try running a quart of trans fluid in your oil for a few thousand miles and see if it helps, sometimes it will dissolve enough of whatever gook there is for a ring to unstick. You won't believe how black the oil will come out afterwards because it will eat the gunk all out of the engine.

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"So many Mustangs, so little time..."

 

Well do new engines still have that stuck ring problem ? Reason I ask if because this shortblock only has about 1000 miles on it, and Spartan engines are being ********* about warrantying it.

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92 Z28 L98 350
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Ported and polished heads, ported stock TPI base, ported plenum, Comp Cams XR270HR-10 cam (lift .495/.502 duration 218/224 lobe separation 110), Edelbrock TES headers, LT4 valve springs, Crane AFPR, Flowmaster catback with LT1 style tips, MSD coil & wires...

"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)

 

A new motor shouldn't, since there's no gunk buildup in it.

A new motor shouldn't have that problem. About the only way for a big compression leak like that would be if somebody broke a ring while assembling it, or destroyed a ring land, or even broke part of the ring land off the piston. That sort of thing is actually fairly easy to do if you get in a hurry and don't pay close attention to what you're doing.

Welcome to the world of low-bid rebuilds... this is a perfect example of why I do my own, and of how you get what you pay for, or don't get what you don't pay for as the case may be.

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"So many Mustangs, so little time..."