Leak Down Test Results 161,000 mile stock shortblock

[Chris@Rvengeperformance]

I performed a leak down test on the front 3 because cylinder 1 and 3 tend to foul plugs and the plug threads are oily. VSS and valve cover gaskets have been replaced.

Engine was stone cold after sitting for three or 4 weeks.

100 PSI inputted

cylinder 1 3 5
92.5 PSI 89 PSI 89 PSI


Seems really good to me for a stone cold engine this old.

The engine normally doesn't smoke but will on occasion when taking off at like 25% throttle when cold. Seems to only do this after sitting.

All of this seems to tell me that the front head needs rebuilt due to bad valve guides.

Quick fix would be to pull the front head, but I also have a nice forged crank here waiting to be installed and transmission work to do, so I'm considering yanking the engine and pulling the heads and crank. I do not want to re-ring with numbers this good since their is a chance of it being worse when I'm done.

When this engine is fully warm it probably only has 5 or 6% leakdown. This agress with the 150-160 PSI compression I have on all cylinders.

The other option is just to keep running it, but it has a tendency to randomly have high knock counts that I feel may be related to oil in the front cylinders. I also have not checked the bearings sinced I replaced them about 25,000 miles ago.

Decisons, decisions. I have a spare truck now, so I really have all winter to work on this if I want.

Mitsubishi really knows how to build a short block. If taken care of these bottom ends will last for eternity. Even with the cast crank, lol.