Okay, I need to consult the gurus! All this is on a 1.6 Spec Miata engine.
At the end of last year, I was starting to see some oily water seepage out of the back of engine. Nothing major, but enough to keep an eye on it. I did a compression check and everything was 170-180 psi. After NCM this year, it became a considerable leak, and now I began overheating. I was also getting combustion gasses in my water, which I thought accelerated the overheating. Oddly enough, it was still registering 170-180 psi. I wasn’t getting water in my oil, but I thought I should change the head gasket anyhow.
I disassembled the head after NCM this year. I didn’t have the head checked by a machine shop, but I did put a straight edge on it before reassembling. It looked fine. So, I replaced the head gasket with OEM, which has fixed the combustion gasses in my water problem. However, I’m still overheating and I’m still leaking a good amount of oily water out of the back of the engine? Still not mixing water or oil in the block or the radiator which has me puzzled. Finally, power seems a little down as well. Yesterday I checked the water pump, it’s impeller is nice and clean and spins well. I checked the coolant flange on the back of the head, it’s still dry as a bone. Compression is now 170, 165, 170, 180 which isn’t ideal, but it’s still within the 15psi that the book recommends.
What do I do next? I have a spare head fresh from the machine shop that was just decked, but it’s an unknown mileage OEM valve train and my current head was built by MaCann, a NE Ohio race shop. I also have one more head gasket on hand to make the swap with. The wild card here is we race at Mid Ohio in a week and I have limited time to "make the call" on what to do. The car runs and drives well still, which has me totally confused. Thanks in advance!!