Anyway, at 258,000 miles, my M30 needs a head gasket. It had been seeping coolant onto the back of the block for a while. I couldn't figure out where it was coming from because I couldn't find any leaks on the hoses back there, but coolant showed up on the bellhousing. I found that the waterpump shaft seal was seeping, so I replaced the waterpump and figured that the coolant had been carried to the back of the engine by the air stream. I had been periodically topping off the coolant.
The car was fine for a 2 hour drive Sunday night, but overheated on the way to work Monday. On the way back Monday evening it overheated again. I popped the hood and there was steam around the back end of the engine. After a little playing with my flashlight, I was able to find a small jet of steam coming out between the block and head.
So obviously, if I tear it down far enough to replace the head gasket, I am *NOT* going to put it back stock. The stock gasket is .070 thick. Cometic makes a gasket for it, so I can get said gasket in any of Cometic's standard thicknesses... with a two week lead time. There is also an ARP stud kit for this engine and I'll just have to use that instead of the stock one-time-use head bolts.
So this weekend I'll tear the head off and measure the piston deck. Nobody knows what the factory piston deck on this engine is, despite the fact that it's been extensively hot-rodded around the world for 40 years. I'll order the gasket thickness that will get my quench clearance down to about 0.040. That will probably bump my compression up by 0.1 or so, but with the better quench clearance, that should actually be *better* for eventual turbo use.
OTOH, there's a '97 M3 S52B32US not far away for $1500... It's a 3.2 with 240 HP and 235 ftlbs. It could bolt into my car using M50 525i engine mount brackets and oil pan and give me a 30 HP boost while actually gaining a little torque vs. the 3.5 litre.
