When to change oil in rebuilt engine
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    When to change oil in rebuilt engine

    Hi, I'm rebuilding a 1984 305 small block Chevy, it's been rebored new Pistons, rings, cam and crank. I've been told to use a zinc additive in the oil, what oil and additive would you recommend and how soon should I change the oil after first start up?

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    Administrator blackpopracing's Avatar
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    Real steel do proper running in oil. Change after 500 miles.

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    Off the Xmas card list kapri's Avatar
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    I use ZDDPlus from Burtons.

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    I would change the oil after 100 miles, unless of course the engine and components were cleaned 100% prior to build up, there's always **** in somewhere.
    If quitters never win, and winners never cheat, then who is the fool who said "Quit while you're ahead"

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    Thanks for the info guys

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    Quote Originally Posted by rodster View Post
    I would change the oil after 100 miles, unless of course the engine and components were cleaned 100% prior to build up, there's always **** in somewhere.
    yep, how cheap is oil and filter compared to what you've spent on the engine.
    need a job done on your project? i may be able to help.

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    It may be open to debate but the procedure we always followed was to start and run the engine for 30 minutes then change the filter, but not the oil. Any crap will be caught by the filter so that's the only item that really needs changing. If it's an expensive or aircraft engine it was also common practice to cut open the filter and check for debris.

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    Quote Originally Posted by NMNeil View Post
    It may be open to debate but the procedure we always followed was to start and run the engine for 30 minutes then change the filter, but not the oil. Any crap will be caught by the filter so that's the only item that really needs changing. If it's an expensive or aircraft engine it was also common practice to cut open the filter and check for debris.
    Much as I would like to buy into thinking car filters see all 100% of the oil (and filter it) prior to it being pumped through to the crank journals and cam bearings & followers, this is not always the case as there is a "pressure relief valve" which, when a pre-determined pressure is reached will crack open and a %age of oil will go directly to the bearings and hence not starve them of oil. This can and will happen at fast idle on start-up, where the oil is thick (due to it not yet reaching operating temperature) which is great but a high pressure will cause the relief valve to open (not good). If you think by increasing the relief valve pressure (by putting washers/spacer behind the spring) you will put off the oil by-passing the filter, you have to remember that the filter element is only paper (not metal meshes as for industrial fluid applications) and if pressure is too great then the paper will collapse, leaving the engine with no filtered oil at all!
    I haven't yet worked out how to get around this issue when having to "bed in a new cam" on a brand new rebuilt (all new parts & rebore) engine where the cam manufacturer stipulates an rpm range (and not to drop below that rpm) for a recommended time period (neighbours allowing), and with all those unfiltered particles bombing around unchallenged or wedging themselves in shell bearings and leaving a signature gouge on the main or big-end journals. Only solution I can see (and making work for yourself) is to run the original cam & followers to bed the new engine components, change oil & filter (after running it a few times), change to new cam & followers + new oil & filter and a mix of diesel engine oil (as this is higher in zinc than petrol engine oil), and then change oil (after about 100-200 miles).
    In the perfect world car filters would filter the oil 100%, the nearest is a centrifugal filter, but these are only seen in heavy trucks (where it is said to extend the life of the oil up to three times), and if you know of car engines with a centrifugal filter let me know.

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    The Camino Kid Britdragster's Avatar
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    I'm about to go through this process myself in a couple of weeks with my new supercharged 383 that I've had built. REMEMBER TO PRIME THE OIL SYSTEM PRIOR TO STARTING FOR THE FIRST TIME. I'm using Valvoline VR1 20/50 with a ZDDP additive for the initial break in on the cam and lifters etc, then drain the oil, remover and cut open the oil filter and check that there are no metal fragments from the cam or lifters during the break in. if all is ok then pop on a new filter and re-fill with oil and repeat the process after 100 miles then 500 miles. After that, if there are no issues, service as normal. I'm assuming you're using a flat tappet cam? If so, then you'll have to go through the motions of breaking in the cam with the lifters. Here's a article that lays it out in simple terms. Rog.
    Flat Tappet Break-in Procedure

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    Quote Originally Posted by Wolselliac View Post
    Much as I would like to buy into thinking car filters see all 100% of the oil (and filter it) prior to it being pumped through to the crank journals and cam bearings & followers, this is not always the case as there is a "pressure relief valve" which, when a pre-determined pressure is reached will crack open and a %age of oil will go directly to the bearings and hence not starve them of oil.
    Not quite.
    The pressure relief valve is inside the oil pump and if the pressure gets too high it simply dumps it back into the oil pan. ALL the oil goes through the filter before it goes to the bearings. Yes the oil filter has a pressure vent valve which will open in there is a 10 PSI difference between the inlet and outlet. this is to stop the filter splitting from the pressure if it gets blocked, which is not an issue in this case.

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