Well my Brabus 3.6 has eaten its way through yet another headgasket , thankfully I have an MLS gasket that PUMPISH made for me. I've been losing oil in this car at the same rate (~1L/300mi) I had done before the rebuild last summer (installed gapless 2nd rings having re-bored a new block out to 92mm). I gave it a compression test today with the following results for cylinder numbers
1: 12.5 bar
2: 12 bar
3: 11.5bar
4: 8.5 bar
5: 13 bar
6: 10.75 bar.
I expected adjacent cylinders to be low on compression. I added a teaspoon of oil to cylinders 4 and 6 and re-checked the values but the compression changed by maybe a quarter of a bar which I don't deem to be significant considering the gauge I used is a Gunson's gauge. My car has manual valve lash adjustment which I adjusted less than 3,000 miles ago. The valve guides were changed about 20,000 miles ago; the last time I had the head off (~5,000 mi) my engineer told me that the guides were fine.

The car idles slowly (just over 500rpm) and rather grumpily with a slight misfire that clears up at around 2000 RPM (it no longer has the hesitation which I have previously posted about though). On the motorway there is little perceivable difference between how it runs now and how it ran 30,000 mi ago. It's very torquey and 90 to 140 is still very impressive. Low down, from a standstill I guess it is slightly slower than its optimum.

I'm wondering whether the valve guides on cylinder 4 are shot (certainly I remember them being darker in colour than the others) and whether this is the cause of my oil consumption. Furthermore, if this is the case then perhaps the worn guides are preventing the valves seating properly? The spark plugs are all dry, the 4th plug has a burgundy colour and the 5th is black, sooty. I'll be opening the engine up tomorrow and having my engineer check the bores for wear and piston deck height (for a possible bent conrod) on Monday. Ideas & guidance would be much appreciated.