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Thread: should I be worried? rebuilt motor burning oil

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    VCVC Member Dan Wilson's Avatar
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    Question should I be worried? rebuilt motor burning oil

    Okay, here is the story. I found a rebuilt 230 standard bore engine and to the best of my knowledge it showed all the signs one would look in a rebuild without 'papers'. I have driven it about 130 miles. At 100 miles I checked the oil and noticed it was down 3/4 of a quart. I am running 10-30 which is what the manual calls for. The engine has tons of power but burns oil and doesn't seem to be in any hurry to break in if indeed it is a break in issue. The oil pressure is between 25-35 depending on rpm. I don't remember this the last time I had a rebuilt 230/250 but then again that was almost 30 years ago. Should I be concerned? Is the oil pressure okay? Should I be running a different viscosity? Is it possible the valve seals are bad or what? Should I do a compression test or will this tell me anything? Thanks for any advice!

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    Administrator smiley's Avatar
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    I've never run that viscosity before. I've always run 20W-50, but it's getting hard to find now. If you aren't seeing a leak or smoke, my amateur guess is perhaps the viscosity.
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    VCVC Member Dan Wilson's Avatar
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    Thumbs up

    hmm......that's interesting. I'm pretty sure I ran 20-50 in my last 3 vans including the one I had rebuilt in the 80's. I double checked the manual and it does recommend 10-30 and I figured why not go with spec? I need to dump the oil soon as I have been told I should do. I'll try the 20-50 if I can find it lol. Any other suggestions are welcomed! Thanks Smiley.

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    VCVC Member digz's Avatar
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    Sometimes it depends on what they put in for rings how quick they seal/seat . Used to run 20w non detergent to break in a set for a while then switch over. seemed to work. One time I ran 10-30 from the get -go on a fresh bore with chromoly rings and I can't recall if they ever seated before I sold it, Tried all kinds of Visc' still used oil. Current engine I did the 20w thing and it sealed.
    64 Project,65 Driver,66 Parts sorta

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    VCVC Charter Member Vanner68's Avatar
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    How long did this engine sit before you got it?


    Might just be valve stem seals dried out.
    Gregg Groff


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    Oil Burning

    If you are burning 3/4 of a quart in 100 miles then you should see some blue smoke. Maybe not all the time depending on the cause. I would advise a leak down test and performance test with vacuum gauge installed. Bad valve guides will show as a vibrating needle on the vacuum gauge, blue smoke during continued throttle off deceleration downhill and intermittent blue smoke on startup after sitting a short time. I prefer a leak down tester over a compression test but it takes a little more time. I do not think a change from 10-30 to 20-50 oil is going to change an oil loss problem like you describe. It could be many things from improperly installed rings, poor cylinder finish to bad valves or guides. If it's not leaking it, it's burning it and there's only so many ways that much oil can get in the combustion chamber. Whatever the cause, you may be looking at a complete re-rebuild. Best wishes.
    108VanGuy...
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    VCVC Member ExEarlyVanner's Avatar
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    Dan are you running synthetic oil or regular motor oil .I have heard you need to use regular motor oil for 8 to 10K miles to break in the engine. Synthetic is a no no to breakin an engine

    Ken
    68 90 6cyl three speed

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    VCVC Member Dan Wilson's Avatar
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    response to Vanner68/ExEarlyVanner

    Running regular oil. Not sure how long it sat. When I bought it, the guy said he had it for 6 months but he bought it from a lady whose husband had it rebuilt for a Nova project but then died and it probably sat in that garage but for how long I don't know. How would it take for seals to dry up?




    Quote Originally Posted by ExEarlyVanner View Post
    Dan are you running synthetic oil or regular motor oil .I have heard you need to use regular motor oil for 8 to 10K miles to break in the engine. Synthetic is a no no to breakin an engine

    Ken

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    VCVC Charter Member Vanner68's Avatar
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    I've seen the seals dry up in a year if the engine wasn't wrapped.
    Gregg Groff


    There's no place like 127.0.0.1

    1968 Chevy G20 108 panel Now with 454 power!

    1965 Chevy G10 panel- OHC Pontiac inline 6

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    VCVC Member Dan Wilson's Avatar
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    Stored in a hot dry garage in the hot and dry foothills of California..................I'm hoping it is seals! I mean this beast just has too much power to be anything else. Updates later...............

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