I have a F20c with 81k miles on it. It runs perfectly, but it seems to be slightly down on power. I have not pulled the head yet, but a compression test shows: 190/190/245/190 wet and roughly 175/180/235/185 dry. Leakdown pushes air through the dipstick. Burns what I would call about an average amount of oil, maybe a quarter per 3000 miles.

I assume my cyl walls are toast? If I check the bores and they are clean, what are the chances of new rings just working?

Assuming the rebuild route is where I will go with the OEM overbore pistons.... Where can I get a torque plate for my local shop to do the block work? Any special specs they should bore to, taper etc? Can I leave my crank and cam bearings/journals alone?

 

Leakdown symptom sure sound like worn rings.

 

Tried a borescope ?

 

oil consumption is pretty good, better than average for an ap1.

 

Check for bent valves. Is there air coming out of the intake manifold or exhaust manifold?

 

Leakdown shows no head issues. It is for sure leaking through dipstick tube on 3 of the 4 cyls.

I am pretty well set on it being pistons/rings/walls.... Hard to find alot of rebuild info on this site though. The whole "doesnt smoke and consumes an average bit of oil" tends to suggest the walls are fine though, and I just ruined my top rings, which makes the rebuild a bit easier as I can use the stock pistons and block.

 

Can anyone link me to a "I rebored my motor and put overbore pistons in" thread? I cant even find out if I can remove the engine from the top without messing with the transmission very much?

 

You sure it's not a head gasket?

 

Wouldn't head gasket not come through dipstick but instead through coolant system...?

 

I just wonder because two adjacent cylinders have low compression.