I have an 1989 YJ with 70,000 miles, with 258 w/rebuilt carter. I bought it at 65,000. Mileage confirmed with maintenance records. Been nuttered and team rushed. All new vacuum lines, well the ones that are left anyway. Had no oil leaks and very little blow-by.
The first winter we had it, we could never get enough heat to warm the cab. I assumed bad thermostat. So I pick one up and tear into it. To my surprise, there was no thermostat intalled.
So put the new one in and now glorious heat. Been fighting oil leaks every since. Blow-by has increased significantly. Added a catch can to the vent side of the valve cover, and just lived with it for a while.
Had some spare time yesterday, so I thought I would check to see how bad the plugs were fouled. The plugs looked great. Clean and tan just like they should. I was expecting them to be encrusted with oil and carbon. Don't have a way to check compression. Also, not getting any smoke from the exhaust, but getting smoke from oil fill hole.
So what do you think is causing the blow-by? Rings, valves, head gasket???
Considering the low mileage, could I get by with a valve job?