Intermix - long post, asking for advice on repair

[Doug427]

I have a 2002 Boxster S. Long story short it has intermix. No water in the oil, but oil in the water. Engine runs well, and VERY strong. I changed the oil cooler, and it didn't change anything. I can only assume it's a cylinder head. Is there anything else it can be within reason? I know I can take it to a shop with Porsche experience, but with what I would have to pay them to diagnose I can pay for half the repair. I have two choices - both involve dropping the engine, which I can do.

First, I can use the existing engine, since it runs so darned well. Remove the heads, send them to the place I read about in Costa Mesa or elsewhere, have them welded up and rebuilt, and reinstall. How hard is it to R&R heads on these engines? I have rebuilt many American and Japanese engines, so I know a bit, but I've never done one of these Porsche engines. Not going to rebuild, just pull the heads and reinstall. Of course while it's out I'll replace clutch, IMS bearing, rear seal, plugs and tubes, IOS, engine and trans mounts, etc. Also, the engine I have now has a chain rattle on startup, which quickly goes away. Not sure what the repair is for that, but if reasonably easy, I'll do that while the engine is out as well. Does anyone know of a link to a good how to on this job? Any ideas on costs for the work on the heads? Any and all info on this job would be greatly appreciated.

Second choice is to get a second hand engine. A new/rebuilt is out of the question for cost reasons. Problem with this, of course, is not knowing what's wrong with the engine I would be buying and installing. I may be trading a known problem for a new, unknown problem.

As best I can tell, a used engine will be between $3K and $4500K. For that price I think I can do a complete top end repair and rebuild on mine, fixing all the suspect parts, chain rattle, IMS, etc. In the end the original engine will still be in the car, and I know the engine is a known quantity. My hesitation is twofold:

-Is it in fact the heads? What else can it possibly be?
-How hard is it to remove and replace the heads, keeping everything in time?

I'm eager to hear what you guys think on this. Your input is greatly appreciated. Hopefully with a little back and forth my options will become clearer. Thanks.