Just bought my GN back in September. First drive out this year, noticed engine was getting a bit warm. Limped car home and sure enough oil looks like a milk shake. Tore into the motor and it looks like its been this way for a while. Some very nasty sludge almost like gel is everywhere. So what I am asking is, Should I tear out the motor completely and build it to what my goals (600-650WHP) are for the car? Or do the shady thing and slap some gaskets in and sell? I'm not a shady guy so I guess I'll go with the first option. Whats a solid build sheet for this engine? Can I keep stock crank and rods? I plan on doing pistons. I guess I'm just looking for some solid insight. Thank you guys!
Any pics of the " Nasty sludge that is everywhere " in your motor, Could be headgasket sealer/cooling system sealer someone dumped in there.
Have you pulled the oil pan yet to see if the gel/sludge is in there too.
What did the head gaskets look like,were they blown, if not then you may have other problems that caused the milk shake .
If it were me i would take it out and put it on a stand, it will make things alot easier no matter what you end up doing.
At the very least that oil pan has to come off and things need cleaning and checking out to see what you are dealing with.
Bearings need to be checked after running milkshake thru them, the head gaskets need replacing if you already pulled the heads.Save your back and pull it out ,I'm guessing it probably needs a rebuild anyway by your description, if not , it's still easier on you if you pull it, and then you can clean up the engine compartment , fix the crack in your drivers side header,fix old oil saturated and possibly broken ground wires,paint stuff etc. etc while it's out.
To answer the crank and rods question,The stock crank flexes alot in these motors when you start to turn up the wick,there is some tricks to help it live(steel caps,girdle,)but you should do a complete forged bottom end,along with steel caps,and or girdle for that kind of power.
600-650 at the wheels is going to get very expensive.
Most of the time ,by the time you are done it has cost twice what you expected and taken 5 times longer.
Good Luck.
ask lots of questions,there are some very knowledgeable people on this site .