I recently had my 3.2 top-end rebuilt with 3.8 Supercup Cams, race valve springs, Ti retainers, rod bolts, new rings, SSIs and MB911 muffler in addition to everything else you might expect. Its now done 1900miles and had its first service and oil change at 1650 miles. It burnt a truckload of oil for the first 1500 miles (circa 7 litres) but it was running in with cheap mineral oil. My mechanic says it will stop using oil now that it is on Castrol RS, and the oil consumption has certainly decreased from about 1100miles onwards. I am currently monitoring the consumption but I am not sure how it will burn less when the RS oil is thinner.
Perhaps more worrying, is that it puffs a little on lift-off / overrun. This was most obvious on a dyno run on Saturday. There is certainly nothing you can see from inside the car - its not that bad. My feeling is that the top-end is not 100% following the rebuild. Maybe a pinched valve stem seal? What else is possible? FYI, this was a 75,000mile engine that never burnt a drop before rebuild.
Interestingly, it made 243.6fwhp on the dyno. We couldn't get any AFRs with the MB911 twin out muffler (I don't entirely understand why) but another car with the same chip was very rich so assuming the same condition there is clearly some horsepower still on the table.
I know what I should do. I have to talk to my engine builder, but any thoughts would be appreciated - at least so I sound like I know what I am talking about.
RB
