Try the seafoam thing. Couple of bucks and may clear it up. If rebuild is needed, do the JY thing.

 

Definitely appreciate the input. I've been seeing the 5 and z codes thrown around. For a JY motor, what should I look for and what should I avoid?

 

Closest to your year model and lowest miles. Check dipstick for any signs of water in oil. Since some places pull the engine and set outside, you may be limeted on valuable info. But being out in the rain and duststorms (like out here) could also make it interesting.

 

The only product that's ever increased and help balance compression in my truck is Cermet, and I tried them all. The first time I used it was 40,000 miles ago. It took about 75 miles when power increase was very noticeable. Just gave it another dose because had a 50lb difference from highest to lowest compression,#8 and #3. Average compression is 175 and highest to lowest difference is 180 to 165 in #8and #3,respectively. Tested it according to FSM 800 miles after adding cermet. Eventually will have to replace or rebuild,but sure makes a difference in the meantime.

 

So I did the oil and added some Lucas stabilizer. I gained 5 to 10lbs of compression, but still well below a hundred. I'm looking at getting a running JY motor, having the geads cleaned up, replacing the oil/water pump and all the seals. Hopefully it will work out.

 

Pistons and rings are cheap for our trucks....on summit a piston is in the $35-45 range...just looked them up myself....if i were you id just rebuild your motor since you know how its been treated and maintained

 

...but then add bearings, machining, gasket set....rods and other hardware if needed, valves....overhaul can be expensive and will take time. JY motor may get back on road faster and cheaper for now, allowing time to rebuild current engine for later use.

 

Ah then thats completly different...i wouldnt put any money in the jy motor...swap it out and use the funds to repair current motor...

I may see things differently because i have my car in case something goes wrong with truck...and the way i am i dont like starting another headache...like i said mine has 228k and i know how its been treated the 50k ive owned it...id rebuild mine before id get a new motor unless my block was cracked...but thats me....

 

could be cracked valve, or blown head gasket

 

It could be, but wouldnt really explain the drastic increase in cylinder presure after adding ome 30 weight in the plug hole. A couple of ounce and the compresion bumped back into the 130s like the others.