The engine is a 4.2 block with a 4.0 head and valve cover mod, with the 4.2 intake manifold and a carburetor, headers on the exhaust, and a 4.0 oil pump and pan, it also has a 4.2 water pump and radiator cause the YJ has a CJ-7 front end.
The main problem is that the engine blows its oil out of the breather filter and it leaks all over the engine and blows onto the exhaust causing a James Bond esc smoke screen on the highway. Consulting the forums from years ago I've done several things trying to fix it, Initially I had a 4.2L valve cover and hadn't changed the pcv valve yet so I tried that and it didn't work, then I changed the valve cover to a 4.0L valve cover with a ccv valve and breather filter, which got me much better vacuum pull through the breather but that hasn't seemed to do anything either. Last thing I did was check the compression on all 6 cylinders all were within tolerance for dry and wet, two of the cylinders did go up in compression more than the other but it was again within tolerance for compression.
My only hope of not throwing this engine out and replacing it is that I have the wrong head gasket for the modification, or that the oil pump and sump being from a 4.0 is causing problems.
If anyone has any advice or has experienced the same issue with this kind of engine mod please let me know.
