Priming the oilways after an engine strip down / rebuild

Seems to me it's difficult, and sometimes impossible, to get the oil pressure up after the engine has been in pieces. Seems the oil pupm won't prime itself if the engine has been dismantled. It's easier at an oil change, where I suppose therre's still some oil left in the pick up and pump.

After draining the battery attempting to see the yellow light go out and the gauge rise, I usually end up with the following which works well for me:

Disconnect pipe between block and oil filter, have someone pour oil into the pipe connector on the block, while you turn the engine BACKWARDS by hand. If you fill through a funnel and see through hose, you can see once the oil pump starts sucking the oil in. You hear it, too. Continue for a while, then start rotating the engine the right direction, and the oil pump is primed. Always have the filter filled with oil. Connect the pipe again, turn engine on starter, plugs out, until you have pressure, several times. Start, and hope for the best.

Obviously, all internal parts should be treated with a quality engine break in grease upon assembly. I don't think modern oils, low on zddp are good enough for breaking in an engine. Also, the experts have some different opinions on the correct way to break in a cam and lifters. I did as recommended by the people who rebuilt my engine, and at least I've never damaged the cam or lifters. Other problems, on the other hand.....

Don't recall the exact procedure, but it's something like first have the oil pressure up, then start it and let it idle at 2500 rpm or so untill it's at operating temperature. Let it cool down totally, start it up and let it idle at 1500 rpm until warm. Take it for a spin, drive it like you would normally, but keep revs rather higg, don't push it in low gears. Rev the engine now and then to bed in piston rings.

Roughly like that, after my memory. I take no responsibilty if you ruin your engine doin it this way:-) I will try and find what they wrote to me about it. I did exactly as they said, and at least this time the engine uses no oil and teh cam and lifters were still the same when I had them out. So the mysterious issues must lie elsewhere...

Tommy

I am a little surprised that there isn't very much in the way of definitive guidance on priming the oilways on the web, at least that I can find. Given that many classic cars are laid up for several months of the year during which time oil may drain down if the engine is not started or turned adequately then I think this is something that should be given more consideration.

Like Tommy I have had a bad experience with my first crab engine rebuild. Up to that time I had only rebuilt in-line A series egines and they seemed to build up oil pressure very quickly on spinning the starter. In fact I remember hunting around the garage for ages in a panic as I became convinced I had left out the "O" ring seal between the engine and gearbox and needed to take it all apart again! I did resolve the problem finally by pouring oil in the feed pipe from the block to the oil filter and rotating the engine backwards to prime the pump. There was no internet in those days and I had just moved home with my job to an area where I didn't have any technical friends to call on.

The best advice I have found on the web was written on a forum by "Stephen S" who I believe may be Stephen Strange who has written excellent extensive guides on the MGB. Post.

There are also several mentions elsewhere of the use of petroleum jelly in the oil pump as Chris suggested. I have also fairly recently seen the use of a modified grease gun used to pump oil into the oilways under pressure through the hole in the block where the pipe to the oil filter is threaded.

Here is an extract from Stephen S as it refers to the MGB, note the reference towards the end to ensure the tappets rotate. I believe his post refers to a new engine build so it is not advisable of course to switch tappets to correct the failure to rotate unless the tappets and /or camshaft are new and have not been bedded in together.


"It is essential to prime the oil pump. Failure to do this will result in all of your handiwork being destroyed due to a lack of oil flow and oil pressure. Install a magnetic oil sump plug (Moss Motors Part # 328-282) and fill the sump. Next, pour oil down the vertical tube of the oil filter stand in order to fill the high-pressure oil gallery and supply oil to the main bearings, then install the oil filter. Finally, if your engine is not equipped with an oil cooler, disconnect the large external oil line that goes to the back corner of the block at the oil filter stand and pour oil into it in order to supply oil to the oil pump. If the engine is equipped with an oil cooler, before installing the oil filter, disconnect the large external oil line that goes to the back corner of the block from the oil cooler and, holding it above the height of the cylinder head, pour oil into it in order to supply oil to the oil pump, then reattach it to the oil cooler and pour oil down the aperture in the oil filter stand in order to fill the oil cooler as well as down the tube of the oil filter stand in order to supply oil to the main bearings, then install the oil filter. Pour a tablespoon of oil down the pushrod passages in order to lubricate the tappets and another tablespoon of oil into each spark plug hole in order to lubricate both the pistons and the rings, and then oil the valve stems. Remove the threaded plug in the forward end of the rocker shaft, and then tilt the engine so that the threaded end of the rocker shaft is higher than its opposite end. Pour oil into the rocker shaft in order to lubricate the bushings of rocker arms and allow time for the oil to run down through the oil passage in both the rear rocker shaft pedestal and cylinder head casting to the bushing at the rear end of the camshaft (Now you know why the engineers decided to have a threaded plug instead of a press-fitted plug as at the other end of the rocker shaft). Replace the threaded plug into the forward end of the rocker shaft, then level the engine. Rotate the engine backwards (counterclockwise / anticlockwise) in order to draw the oil into the oil pump. Once the pump is primed, disconnect the power supply to the fuel pump and turn the engine until your oil pressure gauge gives a reading. The oil cannot drain out of the pump once it is primed because the oil pump draws oil from the sump into the top of the pump and also pumps it out of the top on the other side of the rotor.
Upon first turning over the engine, observe to see if all of the pushrods are rotating. If one or more of the pushrods are not rotating, then the tappets in which they are seated are not spinning in their bores and must be freed or both the tappet and the camshaft lobes will quickly be ruined. This may be corrected by switching tappets into alternate bores. Now you may install the rocker arm cover and its gasket, reconnect the electrical power to the fuel pump, and then start the engine.
Steve S."


Any more thoughts, comments, tips?


David

I think the first thing to do is disconnect the oil pressure gauge to see if it falls back to zero. If so you can discount the gauge which is new and an unknown in the equation. I have read, but never experienced a problem where the oil filter has allegedly held the pressure up so you could try loosening it. The pressure release valve only opens when the pressure is excessive so shouldn't in theory be able to prevent the pressure falling at idle. As you have a new oil pump I wouldn't be surprised to see 40 psi at idle especially if the oil was not thoroughly hot.

regards

David

My rebuilt engine won't go below 45 or so at idle, unless when it was really hot during summer. Sometimes the gauge wavers at hot idle. I haven't worried about it.

I suppose the main thing is that the maximum pressure doesn't go too high, as the pump itself is capable of making extreme pressure. If you have oil coming out of the rocker assembly and no abnormal noises, pointing too a blockage/ lack of lubrication, I wouldn't worry.

Tommy