Thread: Priming a dry engine

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Originally Posted by Rrumbler

In the diagram above you see that the oil is pumped through the filter to the three oil galleys above the camshaft, and follow the path the oil takes. If you keep the pressure up long enough while "priming" the engine, the oil will overflow the lifters and the pushrod tips a bit and run back down through the valley and drip onto the cam lobes.

I may be wrong (please correct me if I'm wrong), but I seem to remember the valley drains offset and not directly over the cam. Again I may be wrong, but I believe the cam is oiled by crank splash (unless you have bottom oiling lifters). I believe this is why it is so critical on a flat tappet cam to break the cam in at 2000+ rpm for 20 min, to ensure the oiling of the cam.
Also, on a new motor I was taught to minimize turning the motor over once the valves were set, to minimize wiping the high pressure lube installed on the cam lobes off before break in.
If you installed a new flat tappet cam and did note use high pressure lube on the lobes, I would recommend removing the cam and installing the lube on the lobes prior to start up.

Originally Posted by 36 sedan

Again I may be wrong, but I believe the cam is oiled by crank splash (unless you have bottom oiling lifters). I believe this is why it is so critical on a flat tappet cam to break the cam in at 2000+ rpm for 20 min, to ensure the oiling of the cam..

Just an "off the cuff" remark, but.. when you mention cam oiling, you need to clarify the cam journals do or may get oil from the oil pump and it is the lobes that are actually oiled by the mist of oil inside the engine caused by the 2K rpm. ( or thereabouts..) SOme folks hear one thing but aren't clear on the topic of how things happen when it comes to cam lubrication. HTH.

Originally Posted by 36 sedan

I may be wrong (please correct me if I'm wrong), but I seem to remember the valley drains offset and not directly over the cam. Again I may be wrong, but I believe the cam is oiled by crank splash (unless you have bottom oiling lifters). I believe this is why it is so critical on a flat tappet cam to break the cam in at 2000+ rpm for 20 min, to ensure the oiling of the cam.
Also, on a new motor I was taught to minimize turning the motor over once the valves were set, to minimize wiping the high pressure lube installed on the cam lobes off before break in.
If you installed a new flat tappet cam and did note use high pressure lube on the lobes, I would recommend removing the cam and installing the lube on the lobes prior to start up.

The drain back holes in the valley are between the lifter bosses on Gen I blocks (on Gen II "roller" blocks, they are different, but cam lobe oiling is not so much of an issue on a roller if good assembly techniques are followed). When the oil from static priming, eg. with a drill motor, runs down the pushrods and seeps out around the top of the lifters and the bosses, it runs back through the holes, down the lifter bosses under the web, and down the lifter body to the cam lobes. In operation, yes, the primary lubrication of the cam lobes is from splash/mist, but for pre-startup, the combination of the high pressure lube and the oil from static priming should be sufficient that the risk of galling on starting should not be a concern.

In my early wrench years, the gentleman I shadowed taught me that slowly rotating a fresh engine, while static oiling, distributed the oil around the bearings, the better to provide protection during initial start, even though the bearings had been oiled by hand during assembly, and we never talked about camshaft lubrication; it seemed it was a given, what with the assembly lube and oil that got onto the cam from priming.

Agreed, I would not install any flat tappet cam without a thorough coat of camshaft assembly lube, and I would limit the amount of rotation of the crank to only two complete turns - rotates the camshaft only once.

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Originally Posted by Rrumbler

The drain back holes in the valley are between the lifter bosses on Gen I blocks (on Gen II "roller" blocks, they are different, but cam lobe oiling is not so much of an issue on a roller if good assembly techniques are followed). When the oil from static priming, eg. with a drill motor, runs down the pushrods and seeps out around the top of the lifters and the bosses, it runs back through the holes, down the lifter bosses under the web, and down the lifter body to the cam lobes. In operation, yes, the primary lubrication of the cam lobes is from splash/mist, but for pre-startup, the combination of the high pressure lube and the oil from static priming should be sufficient that the risk of galling on starting should not be a concern.

In my early wrench years, the gentleman I shadowed taught me that slowly rotating a fresh engine, while static oiling, distributed the oil around the bearings, the better to provide protection during initial start, even though the bearings had been oiled by hand during assembly, and we never talked about camshaft lubrication; it seemed it was a given, what with the assembly lube and oil that got onto the cam from priming.

Agreed, I would not install any flat tappet cam without a thorough coat of camshaft assembly lube, and I would limit the amount of rotation of the crank to only two complete turns - rotates the camshaft only once.

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Thank you.