Where's the oil gone?

[droptop]

  I have a hugely puzzling situation with the oil level in my '78 spider.
On Monday evening, I brought the car out of the garage to repair the rear exhaust box hanger which was moving about causing intermittent banging and scraping noise (See post entitled "Bang Bang").
Anyway, I drove it back in  when I was finished and yesterday, I removed the sparkplugs to check them as since the car had covered 300 miles since I recomissioned it, I just wanted to get an idea of how it was running. The plugs were a good healthy colour, but I found no.3 to be a short reach plug which I must have fitted by accident so I decided to renew all four. No. 3 thread had been damaged I guess by the plug firing up in the threaded portion so I cleaned the thread with a plug tap and fitted the four pluge and started the engine.
Well, the harsh knocking that it produced scared the bejaysus out of me. It only ran for as long as it took me to regiser the noise and switch it off again. It sounded like a big end bearing had let go, but seemed to be coming from the exhaust cam. I removed the four plugs and cranked the engine which cranked without issue, then I replaced the plugs one at a time, cranking after each was fitted. Again all was well.
I reattached the HT leads and again when it started, I thought the exhaust cam was going io leave the head.
Now, considering that 12 hours before, I had started the car without incident, this was a puzzle. It had travelled literally 8 metres before being parked for the night.
I did the whole remove the plugs thing again but found nothing.
I dipped it for oil and found nothing on the dipstick! I had done the sump gasket just 300 miles previously and had been monitoring it for leaks since and had checked the oil twice and as the car is parked on a dry clean floor, a leak would be easy to see. The plugs showed no signs of having burned the oil and my garage is 100% secure and secluded so no one could have drained it, I am indeed puzzled.
 Any ideas, anyone?
My friend blames the fact that the reg. of the car is 666FZB, but I am inclined to discount the supernatural

[MattNoVAT]

If its definately got no oil I'd drain it to check how much oil is actually left in it and then replace it - just to be on the safe side.
Are you reading it off the dip stick or the internal oil level gauge?

As for the noise coming from the exhaust cam, could the exhaust cam wheel have slipped a tooth on the belt?

I'd be taking the exhaust cam cover off just for a visual inspection first.

Double check the timing and then have a poke about in the chambers to see if there is anything rattling around in there - I use one of those extending magnet things (like a car antenna with a small magnet on the end thats used for retrieving dropped nuts & bolts)

If nothing shows up then I'd be preparing myself for taking the head off to see whats going on.  Maybe the No 3 short reach plug is masking the fact that No3 valve has burnt out and thats where your oil has gone and there is a big of broken valve rattling around??

Ive seen a cams sheered, burnt valves that break up, slipped belts, if the big ends go it usually starts with light knocking getting progressively worse/louder until such time that people in the street start looking at you in an odd way as you drive home with the crank violently trying to escape the block by any means possible - But it could be any number of things. 

How long was the engine sat idle before you recommissioned it?  300 miles under its belt could be enough to kill off the big end shells bearings. (beats my record of 623 miles after a recommission)

[droptop]

Thanks for the reply, Matt. I didn't mean that the engine was rebuilt 300 miles ago. The car sat in a shed for 22 years until I got it in April this year. It had been kept started and moved so nothing was siezed so I just  changed the oil, water pump, timing belt, tensioner, radaitor, fan stat, coolant, plugs, points, cap, rotor, coil, HT leads, sump gasket, rubber fuel lines and battery before driving it. As there was only 33,100 miles  on it, I felt confident running it after this modest amount of work.
I started it today after topping up the oil and let it warm without incident. There isn't any undue harshness in the engine aside from the need to shim the tappets and no oil leaked after 15 mins. running.
I am planning on driving it this evening and see what happens after it comes under a little pressure.
If the engine has to come out, I think that it will be off the road for the rest of the year as I don't have the time to deal with it quickly enough before the season ends

[lanciamad]

5 litres of oil gone missing without a trace of leakage is impressive. A hard one to explain. What was and is the oil pressure like now?

[droptop]

The needle is showing the pressure at idle (about 8-900 rpm) to be about 1/3 of the way between the red zones on the gauge which is where it always sat. When the car is revved, the needle goes about 2/3 of the way across.
I didn't get to drive it yesterday, but I did run it up to operating temperature until the fan came on and there was no oil underneath or no drips or seepage and when it was revved to about 3500 there was no smoke of any colour out of the exhaust.
What's the story with checking the oil level with that button on the dash? I have tried that several times since getting the car and nothing moves or lights or anything else to indicate the level.

[thecolonel]

the dash button links to a vacuum dip, there should be a thin plastic tube on the dipstick.
when the button is pushed and released the weight of oil on/in the dipstick moves the
pointer on the dash. (these often fail due to being disconnected or diaphram failure.

[andybeta]

the dash button links to a vacuum dip, there should be a thin plastic tube on the dipstick.
when the button is pushed and released the weight of oil on/in the dipstick moves the
pointer on the dash. (these often fail due to being disconnected or diaphram failure.

The one on my VX was fine until the plastic dipstick snapped as Lancia stupidly made them out of plastic that became brittle when exposed to hot oil.

Why doesn't the OP take the sump plug out and drain the oil measuring how much comes out, taking into account any volume in the filter and oil cooler and lines?

[droptop]

I guess I have some sort of failure as nothing happens, but what you never had, you never miss.
I am going to disconnect the tube from the dipstick and plug the top of the dipstick as it is very fiddley trying to read with the tube attached anyway.
Still no idea what happened to the oil!