Is the arrow marked hole where oil is fed to the rockers?

If this is true, how long does it take for the oil to reach the rocker arms on a new engine build?

No, it’s the one right in the corner

It takes quite a while to come up to the top end. I’d suggest covering them all in oil with the rocker cover off prior to the first start. You will probably need to have the engine running as the feed comes from a slot in the cam and it’s not a huge volume

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Best thing to do (other than my method below) is to leave the spark plugs out and turn the engine over with the starter motor until oil starts coming out of the rocker shaft. The engine will spin fast for a little bit until it picks up oil pressure, then slows down and as it has to push against the oil pressure. Also a good idea to "reverse prime" the oil pump by taking the oil cooler/filter outlet off the block and use a funnel to fill it (the outlet from the engine that is) with oil. Put the car in 4th gear and push it backwards to send the oil back down into the oil pump and pickup pipe. Do it a few times and you can be sure that the oil pump has oil in it as they can "air lock". Early this year I hadn't used my car for a few months, I started it up and there was no oil pressure, I left it running and nothing on the gauge. I took the oil filter outlet off the block and it was dry, turned it over for a bit and nothing came up, so reverse primed it as described. Turned it over on the starter and oil pressure came up, started it and no issues.

However, I have a pressure tank I use to fill the oil galleries on a new engine build. The tank has a hose that screws into the oil pressure gauge outlet on the block. I put about 1l of oil in the tank, then pressurise it with the air compressor, then open the valve on the tank and the oil goes into the engine under pressure. You can hear it bubbling through the block and popping air pockets. After re-pressurising a couple of times oil goes all the way up to the rockers, through the crankshaft, everywhere. Basically the engine has oil pressure before even turning the crankshaft. I used to borrow one off a mechanic mate of mine, but then I bought/made my own.

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did I tell you that I won a trophy?

That’s particularly clever Simon.
I have a non Mini engine to build and I think I’ll prime it this way.
I once built a P76 V8 and the “book” states to run it at 2000 rpm until the oil flows out of the rockers. It took a couple of minutes before all of the followers and rockers went silent. The engine performed faultlessly for many years. But I had drowned every part in a mixture of engine oil and molybdenum disulphide during the build to ensure everything was slippery

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Find a job you love and you will never have to go to work !

I’ve done the reverse prime a few times on new builds as even with the plugs out i didnt see pressure come up. About a dozen squirts with an oil can.

I’ve seen professional engine builders use the pressurised tank which Simon talks about, this guy shows it in action https://youtu.be/tOYLlr8uQ8k . I dont have a compressor, i’ve wondered if I could rig up something off a 8L weed sprayer hand pump.

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1966 Mini Deluxe - “Gabby” 34 years under restoration and counting...
1970 MGBGT
1959 MGA

Here's the doover I use



No idea where I got them from, might have been ebay, but did come in a two pack red and blue like these, and about the same price.

https://au.jbtools.com/titan-tools-1942 ... twin-pack/

The spray nozzle just unscrews and it has an NPT thread or something, a couple of quick connect fittings, a BSP nipple in the block and a bit of hose and its done...

To be honest I'll actually fill it with oil a couple of times and keep pumping oil through, just gotta watch you don't run the tank empty cos it'll push air.

Last time I went a bit further and had a T piece screwed into the block with a pressure gauge, the cool thing about that is you can start the engine from under the bonnet with everything still connected and see the gauge come up.

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did I tell you that I won a trophy?

There were some aftermarket oil pumps without a chamfer on the edge, I had the same problem. They sat clear of the gasket. Wouldn't prime.
After removing twice I woke up and sanded the corner off.
After priming I leave the pipe or hose off until oil pumps without air in it then connect it.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.