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Discussion Starter #1 (Edited)
So after a lot of work and education, I got the 505 running really well. I cleaned up a lot of the over-fueling issues. This thing runs great (to me at least, but I'm new). However, it is using a surprising amount of oil, I do have a leaky rear main seal. When I get on it, it first has a small cloud of oil smoke, but then the exhaust cleans up. Admittedly, this new engine has roughly 2,000 miles on it. However, on first start-up, I messed it up trying to get it to run by having a leaking carb, keeping it over-fueled and kept it at a low rpm for too long. I think it might be a ring seal issue (I know I have posted about it before).

I decided to bore scope my cylinders. To me, it looks like a combination of oil and carbon. Compression was around 9.25:1, before the piston deposits. The old plugs were always carbon fouled, and again, my fault, I babied the crap out of it (under 4k rpms and only a quarter throttle). So between the low rpm, rich idle and rich transition circuit, I messed this one up!

Compression tests came back under 5% variance between all cylinders and the plugs are looking okay now, besides cylinder 6, it looks oily. I do not remember what piston ring material my rings are made of.

This is my first full summer to enjoy the car after owning it for 5 years, and I just want to enjoy it. I live in the Pacific Northwest, so come October, this car will not see outside until June. What would be some suggestions as a next step?

1. I was thinking of trying GM top end cleaner. See if it helps rings seat (might be too late with too many miles) and seeing if the issues come back. I have heard mixed options about the potential of dislodging carbon and stuck valves. Tom Wilson in his book Big Block Chevy Engines is against this method I believe.
2. Pull the heads and clean pistons and valve train?
3. Leak down test and possible full rebuild with new rings come winter, or sooner.
 

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Top engine cleaner does really do a number on cleaning out all the gunk. Do you run a Hi volume oil pump? I did on my last 461 and there was oil everywhere, tops of pistons, chambers and in the cylinders. Took it apart and put in a stock pump and have not had any oil issues since.
 

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Discussion Starter #3
I am running a high volume Melling oil pump with a Moroso deep stroker pan. I am also having oil control issues through my PCV, breather and gaskets. I have a mist of oil everywhere. I recently installed an ME Wagner PCV, and a catch can between the PCV and carb.

I am seeing pressures in the 80s on startup. Once the 10W-30 heats up, I am seeing 20-25 psi at idle and 60s psi under load.
 

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I second 68 Chevelle's recommnedation of GM TOP Engine Cleaner, you;re #1 pick. , if they still sell the stuff. Beware it puts up one helluva plume of noxious exhaust when you fire it back up! Do it right before an oil change.
 

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Discussion Starter #7
I actually have a can of GM top engine cleaner that I have been waiting to use. This is a new engine with tight tolerances. Maybe I should go with a stock oil pump. Any thoughts?
 

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id do a leakdown on it before tearing it apart. If all checks out go ahead and run your cleaner....get the engine good and warm & go beat on it for awhile.
in the 70s we would take a spray bottle of warm water and while holding the throttle at 2k slowly spray a mist down the carb for a bit.
 

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"Leak down test and possible full rebuild with new rings come winter, or sooner."

What type pistons are fitted (cast or forged?), and what piston to bore clearances????

Too much clearance, pistons rock ove in the bore, stay rocked over through the piston travel, and then do not support the ring sealing, especially a single piece oil control ring, but, even with a composite 3 or 4 piece oil ring.
 

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Discussion Starter #11
Thank you for everyone's input.

Forged pistons, but I cannot recall rings or clearance, its been a while since the build.

I called up Chris at Straub Tech, and he said use the GM top end cleaner or seafoam and drive it.
 

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When you get it pulled apart, please carefully measure the piston clearances, front to rear of skirt, at the pin center, vs the bore diameter. Too large, piston doesn't allow rings to seal against the cylinder because the piston is cocked in the too large bore.
 

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Discussion Starter #13
When you get it pulled apart, please carefully measure the piston clearances, front to rear of skirt, at the pin center, vs the bore diameter. Too large, piston doesn't allow rings to seal against the cylinder because the piston is cocked in the too large bore.
Thank you for your advice. This will be my first build on my own. I do have a leak down tester and will test before tear down.
 

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Here,s my two cents worth . You more than likely gas washed and ruined the ring seal by your leaking carb and over fueling . You may have also done other damage because of oil dilution. My suggestion would be to take it all apart have the blockhoned for moly rings have it cooked and new cam bearings . Buy all new hastings rings and new bearings main and rod . Get rid of the high volume oil pump you dont need it. The std one with the right spring is all you need . Check all your clearances at this time polish the crank with a worn out belt so it only polishes. I would also take the heads apart check for guide wear and polish the stems for good valve action install new real; good seals like toke products they make the best valve seals used them for years. Then reassemble repair all your fuel issues and you will be good. I dont think putting sea foam tvf or g/m top eng cleaner is going to solve any of you r problems. I will probably get a lot of negative flack for what i just said , but i think i am spot on by what you stated . I know this isnt what you wanted to hear but good luck which ever way you go. Everything is a learning experience life love marriage cars friendships and it takes decades to semi understand and sort it all out. There is a lot of salt you have to eat before you can taste the honey. I have been around long enough to know this to be factual . Good luck. Alex
 

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Do you have any baffles in the valve cover that involve the tube that goes to the PCV or the catch can. With no baffle it is just going to suck the oil up. If you look at the ME Wagner website they also talk about bad baffles that can actually make things worse and suck the oil out of the valve cover like a straw. On the LS motors GM has an elaborate system to try to keep the oil out of the intake. On mine the stud gridle is the baffle. If you could give us a motor shot to see how you run the PCV catch can. I would try some simple solutions first but - z27 - might also be correct. If you do a lot a of pooping around town you might look at also a hotter plug - you don't have a lot of compression 9.25 to 1 and your cam is good size (not huge but not small either).
 

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If you would, once it is apart, remove the rings from a couple of the pistons and insert them back into their bores. Then, piston in one place in the bore, try to rock the skirts back and forth in the bore, and see if the piston is moving a lot, or, the skirt to bore clearances are enough to only allow minimum rocking in the bore. Lots of rock, rings don't seal well, not so much rock over, much better ring seal.
 

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Discussion Starter #17
If you would, once it is apart, remove the rings from a couple of the pistons and insert them back into their bores. Then, piston in one place in the bore, try to rock the skirts back and forth in the bore, and see if the piston is moving a lot, or, the skirt to bore clearances are enough to only allow minimum rocking in the bore. Lots of rock, rings don't seal well, not so much rock over, much better ring seal.
This might be a newbie (does anyone say that anymore?) question, but if the pistons do rock too much, is there a wider piston ring that can be had? Or would I have to bore to the next size and get new pistons? With a 505, I am already pretty bored out, so maybe a sleeve? I apologize again, I am new to engine building. I do however have the classic books to help me through the process.
 

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Discussion Starter #18
Here,s my two cents worth . You more than likely gas washed and ruined the ring seal by your leaking carb and over fueling . You may have also done other damage because of oil dilution. My suggestion would be to take it all apart have the blockhoned for moly rings have it cooked and new cam bearings . Buy all new hastings rings and new bearings main and rod . Get rid of the high volume oil pump you dont need it. The std one with the right spring is all you need . Check all your clearances at this time polish the crank with a worn out belt so it only polishes. I would also take the heads apart check for guide wear and polish the stems for good valve action install new real; good seals like toke products they make the best valve seals used them for years. Then reassemble repair all your fuel issues and you will be good. I dont think putting sea foam tvf or g/m top eng cleaner is going to solve any of you r problems. I will probably get a lot of negative flack for what i just said , but i think i am spot on by what you stated . I know this isnt what you wanted to hear but good luck which ever way you go. Everything is a learning experience life love marriage cars friendships and it takes decades to semi understand and sort it all out. There is a lot of salt you have to eat before you can taste the honey. I have been around long enough to know this to be factual . Good luck. Alex

My apologies for not seeing this post sooner. My initial gut reaction was that I fuel washed the rings. I am planning on taking it apart this winter. This is the first summer I have been able to enjoy it since buying it 5 years ago, so I am just going to drive it. Typically I am the fix something right away mentality, but after seeing it sit for so long, I am not tearing it apart again with 2 months left to go in summer and not being able to drive it for 8 months.

I should add that I live in the pacific northwest, so I wont see sun for 8 months! All my previous summers I was fighting wildfires, so I am not going to miss out. Not another summer!
 

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Discussion Starter #19
Do you have any baffles in the valve cover that involve the tube that goes to the PCV or the catch can. With no baffle it is just going to suck the oil up. If you look at the ME Wagner website they also talk about bad baffles that can actually make things worse and suck the oil out of the valve cover like a straw. On the LS motors GM has an elaborate system to try to keep the oil out of the intake. On mine the stud gridle is the baffle. If you could give us a motor shot to see how you run the PCV catch can. I would try some simple solutions first but - z27 - might also be correct. If you do a lot a of pooping around town you might look at also a hotter plug - you don't have a lot of compression 9.25 to 1 and your cam is good size (not huge but not small either).

Also, I do have a baffled valve cover, but the baffles absolutely suck! They are stock type baffles and really do not do a good job. I am looking for another set of valve covers. I am also running FR5 NGK spark plugs which cross to the 3924 Autolites
 

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If the pistons rock over too much, there are two alternatives, IF the bore is in tolerance, new pistons, and if not, bore hads been 'race clearanced", bore and new pistons, set up tight, so the pistons do not rock over excessively.

ONLY oil ring sets that work are 3 piece, two scrapers, one spreader. Single oil control cast ring, too much bore clearance, piston rock over, NO fix but bore and new pistons.
 
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