3K-U Mechanical advancing

[altezzaclub]

Well, its good that the advance is much better, but 110psi is pretty bad for an engine. The usual story is to pour a teaspoon of engine oil down a spark plug hole and redo the compression test a couple of minutes later. The theory is that the oil sits on the rings and helps seal them to the bore, so any increase in compression is the result of worn rings being sealed. If it doesn't hit over 150psi (and I reckon that's unlikely!) then the leakage is through the valves being burnt.

Ring job, expensive and complicated..    Valve job, simpler and much cheaper.

The tricky bit is the amount of oil to put in... enough to flow across the piston (so do it on a warm engine) and get onto the rings, but too much will occupy combustion volume and put the compression readings up anyway. I've never done it, I usually take the head off and grind the valves, and at the same time I can see the lip on the bore and feel the slop in the pistons from worn rings. Do the valve clearances before you ever take a head off, the gaps can wear away until the pushrod starts to hold the valve off the seat and you lose compression.  That's the only problem with the inlets, but hot combustion gases going out a tiny gap past an exhaust valve burns the valve and seat away quickly.

Certainly 180psi will give you a much more powerful motor than 110psi! The fuel economy should improve now, 52deg is going to help that, 7.0 to 7.5L/100km would be good, and under 7 on a trip.  The solution to the plug colour may appear later, its a puzzle..