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The Prior owner claimed this engine was rebuilt 13 years and ~10,000 miles ago. I was always skeptic as no paper work was available. This weekend I replaced the oil pan gasket and found sludge in the pan (half a cup). Here are some pictures of the pistons and such. I'm not an engine builder but to my eyes there seems to be way too much varnish on the surfaces for engine that supposedly has 10-12k on it.
what do you guys think? How fast is sludge form? How fast does varnish form on the internal surfaces? (additional pictures of timing chain and main bearing posted lower in thread)
Varnish on the pistons mean little. Most people probably don't have the pistons cleaned during a rebuild. Sludge is a different matter, as it is more indicative of the passage of time. I, myself, would probably dismiss that claim. Is there an issue with the engine?
The oil filter attaches to a adaptor on the block that has a "By-Pass" allowing oil to skip the filtering process. You could always swap the adaptor out, not knowing if its working properly or not.
As far as a rebuild, most people stamp the cylinder number on the bottom of the rod cap. Not seeing any indication of that, but who knows?
Any rebuild should have a big envelope included containing almost every receipt for parts & labor, what was done to it. Just common courtesy and good practice. But again, who knows?
Never seen a crank turn to 24 krt gold before. Makes it worth more. Very strange indeed.
Add: The more I look the more varnish I see. I believe varnish comes from fuel and not oil. So, I wonder if this engine saw fuel in the oil pan from other issues? It happens.
Last edited by HeadsU.P.; Jan 26, 2021 at 09:24 AM.
I guess you don't have a head off. If you ever do, measure the cylinder bore. If its stock the engine probably hasn't been rebuilt. I agree 1/2 cup of sludge in the pan suggests a lot more than 10,000 miles.
From: At my Bar drinking and wrenching in Lafayette Colorado
Somebody has had the oil pan gasket off before: That's not a factory-installed oil pan gasket. Most people don't pull the oil pan and change the pan gasket just for entertainment, so the engine has had some type of work done to it...
The term "rebuilt" has no absolute meaning.
For many a backyard mechanic rebuilt means simply replacing the crank/rod bearings and rings with the block still in the car.
Thanks for all the feedback! interesting point regarding stamping on rod caps. Taking a closer look - YES I do see 1,2,3....8 in sequence on each rod cap. Did GM stamp rod caps at the the factory? Perhaps this is an indicator the engine was rebuilt? Should i take off one of the main or rod caps? Any stamping I can maybe find there that would confirm one way or another? Current mileage 85k. Prior owner did mention that the car sat alot. maybe he did not Change oil too often? Engine otherwise fine (but dont have anything to compare to. I welcome any other ideas or thoughts.
Sludge can build up fast with many short starts/runs where the engine doesn't get hot.
Does it run OK? IF so, I'd leave it alone.
FYI per the sludge. Be careful using any additives/cleaners to break down the varnish or sludge.
Look close at the con rod nuts....see the witness marks of a previous install (spiral) as the nuts are now upside down? (Not all)....it has been apart.
Somebody has had the oil pan gasket off before: That's not a factory-installed oil pan gasket. Most people don't pull the oil pan and change the pan gasket just for entertainment, so the engine has had some type of work done to it...
Unless its a Rear Main Seal issue, then a quick replacement. Nothing else.
Agaon, Make sure you introduce Zinc to that oil system. I see some minor scoring on the cylinder walls and the cam lobes are not real happy either.
Last edited by HeadsU.P.; Jan 26, 2021 at 12:51 PM.
The term "rebuilt" has no absolute meaning.
For many a backyard mechanic rebuilt means simply replacing the crank/rod bearings and rings with the block still in the car.
I had a friend who took his car in for a motor to be rebuilt. Asked more questions and finally figured out all they did was replace the head gaskets that were leaking. Shop charges - honest amount on invoice but he insisted it was rebuilt
I like the forensic analysis of the given data. Here's one more data point.
Jebby- excellent observation regardiglding some nuts being on upside down. This definitely suggests that the Caps were off. A good sign this engine was a part to some degree?
A few months ago I had the engine out for cosmetic restoration. While at it I took the timing cover off. Here is what found.... I measured 0.5 inch deflections Slack. Most of the guys on the form said it was normal and within limits but I still went a head and replaced it.
Don't pay attention to the condition of the the paint as an indicator. This picture was taken after wire brushing the block prepping it for a new coat of paint.
by the way the reason why I took the oil pan off was to address the Leaky rear main seal..
I like your style. When you remove a part, you put the bolt right back in the hole it came from. I do the exact same thing and have for decades. Good habit.
You'll never loose track of hardware.
I hate it when my unorganized buddies throw everything in a Zip-Lock bag of hodge podge nuts & bolts. Someone will always "borrow" a bolt from the bag never to be seen again..
I like your style. When you remove a part, you put the bolt right back in the hole it came from. I do the exact same thing and have for decades. Good habit.
You'll never loose track of hardware.
I hate it when my unorganized buddies throw everything in a Zip-Lock bag of hodge podge nuts & bolts. Someone will always "borrow" a bolt from the bag never to be seen again..
I once lent my shop to a friend who had another friend (who was a 'professional' mechanic) swap the motor in his car. As he disassembled the engine, he threw every nut, bolt, washer, and a few other things into one big box. As an amateur I was in no position to criticize, but I couldn't watch.
The PO may have had the engine rebuilt 10K ago...but he likely didn't change the oil and filter since then, if it had that much sludge in the pan. As mentioned, change to a good quality oil with some detergent [already] in it. Then run for 500-1000 miles and change filter and to your preferred oil type.
The term "rebuilt" has no absolute meaning.
For many a backyard mechanic rebuilt means simply replacing the crank/rod bearings and rings with the block still in the car.
Was this engine rebuilt???
