flyingbrass

1986 22R pickup with 116K miles (the odometer is deceptive: many short trips over the years).

#1 170
#2 115 wet: 132
#3 172
#4 190

I was going to do a leakdown test to confirm my longstanding suspicion of a burned exhaust valve, but I read about holding a piece of paper on the tail pipe at idle and watching for suction. I'm surprised to find it actually works. Almost tore my Autozone receipt in half.

I've had this going on for quite some time. My questions are:

1) Does the increase in the wet reading of #2 (using a teaspoon or so of engine oil) mean anything? I'm thinking maybe enough oil saturated the weak portion of the burned exhaust valve to boost the reading that much. Is it normal to see that much increase if the rings are ok? Or, do I maybe also have something else going on? If my bottom end is ok I only need to address the head.

2) I've driven somewhere around 16K miles since I first suspected a burned valve. Will continuing to drive it more harm the head to an irreparable extent? Is there a point of no return?

3) I'm guessing the overly high compression in #4 is probably due to carbon buildup related to the #2 problem. Would decarbonizing with water help, hurt or make little difference in the short term?

Apart from only getting 16-17 MPG (used to be 20ish way back when), a "putt..putt" sound in the exhaust, and somewhat reduced power, she still runs ok. Surprisingly, all plugs looked pretty good. Plug #2 was very difficult to get out and reinstall even using a new plug and a healthy coat of anti-seize. I won't remove it again until I pull the head, and assuming I reuse this head I'll have the shop chase or helicoil it.