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Discussion Starter #1
This is a long and rather sad story, but here goes!

The pontiac 400 in my '78 Trans Am was blowing a lot of smoke and seemed to have a dead miss so I decided to investigate. I had recently installed a set of heads purchased on ebay that were described to be in 'running condition.' The motor ran very well before the head swap although it did burn about 1/2 quart every 2500 miles. I ran the ebay heads for approximately 200 miles.

So I tore it down and found piston ring shards in the lifter valley area. Wish I had saved the pieces to post a picture but didnt think of it at the time. Amazingly it appears no trash got into the bearings because the motor still carries 25-60 pounds of oil pressure. On the off chance the shards were not piston rings but some other internal part that can shatter without causing any problems (har har), I decided to re-assemble it with the original 6X heads and hope for the best.

Checked compression, #5 has 75lbs, #7 has 0, so the motor should be very easy to turn over. The starter has a hard time firing the engine, like timing is off, but it will still run, albeit poorly, and I dont think anything is internally holding it from turning over because oil pressure is still good. I do not have a timing light so I cant post what it is set at, but the timing has not been messed with since the days when the motor ran well. Why is the motor having a hard time turning itself over? Why does the oil not smell like gasoline if the #7 cylinder has zero compression?
 

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Compression

Doc here :pimp:

What are the rest of the cylinders reading at? are they lower than 125?

Are You sure those were Ring Shards in the valley, Did you check the oil, and drain the filter into a screen looking for more?

Is the Oil Milky?

If you got a healthy Backfire during start up on the first head swap, you could have jumped time on an old weak timing chain..

The indications would be low compression all the way around. Static timing off, no sync between #1 TDC, compression , valves closed, and timing mark line up...

THE OTHER thing it could be is the head gasket Compression Rings between 5 and 7 Head gasket have blown out and came to rest in the valley..

(Stranger things have happened, I guess, or they were blown on the 2 nd head swap and just fell in there)

Are you leaking (using) Water?

Are you getting water in the oil?

Do the compression all the way around, Check static timing , I think you'll find your problem lies somewhere between the two...

Doc :pimp:
 

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Discussion Starter #3
All cylinders read between 130 and 145, with the exception of the two I mentioned.

Im not absolutely sure the pieces were piston rings, they were definately metal and don't resemble anything else I can think of. They were too thick to be pieces of head gasket. There were only two fragments and they were both very small, approximately 1/8th inch by 1/8th inch, maybe even a little smaller than that and they had a smooth curve like a ring would. I have not drained the oil yet, hopefully that will get done tomorrow.

The timing chain is only 1000 miles old and it is very unlikely that it jumped.

The head gaskets are new and since the oil is not milky, they are most likely not the source of the problem.

The lifters on the cylinder with zero compression also seem to be in good condition, I can see the rockers moving with the engine running without valve covers.

What still has me confused is why the motor is having a hard time turning over???
 

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I know this isn't any help but how in the world would piston rings get in the lifter valley without some huge gaping hole? How would they get out of the cylinder? and then into the valley??
 

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Discussion Starter #5
One of two ways I suppose, the piston ring could break, fall into the bottem end, and be pushed up through the oil passages, or perhaps the block was not throughly prepped before rebuild and fragments were left.
The oil has been changed many times since its only rebuild 14,000 miles ago and the lifter valley cover has been removed three times in that period and up until the latest removal of the valley cover, I never noticed any metal fragments inside the motor or in the oil.
Because of that I would assume the ring broke and fell into the bottom end, unfortunately probably causing some severe scarring of the cylinder walls on the way down.
 

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Possible I guess but if you fragged it bad enough to send rings to the bottom of the pan you do have a serious problem. Of course I guess you do have zero compression on one hole. Which brings me to conclude that a tear down is in order.
 

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Try 3-4 good squirts of oil in the low cyl's & recheck comp, if it comes up, your rings are damaged, if not, bad valves, loosen the rockers on those two cyl's and put air on the cyl, and listen for air in the exh, carb or crankcase!
 

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Is the motor hard to turn over with a breaker bar? The broken pieces maybe starteing to lock the motor up. My feelings on this is that you better do a complete tear down on this one before tear the rebuildable pieces up.
 

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Discussion Starter #9
Pulling the motor seemed like the thing to do, but before that I thought Id ask around on here to make sure I didnt overlook something simple. Thanks for the help!
 
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