I have recently run into a large problem with my 142. It hasn't been running all that well for some time (very rough idle). I just looked at the spark plugs and they are oily! I checked the timing and point gap and they are normal. (points are new) Also, when trying to turn the engine by hand (turning the fan belt) I cannot turn it all the way around, the belt just slips on the crank pulley. I have pretty much come to the conclusion that the engine will need a full rebuild. If anyone has had similar symptoms with their B20 please let me know!
P.S If anyone knows of a sound B20 engine for sale for a reasonable price let me know

Thanks,

Chris (Calgary, Canada)

Plugs wet with oil are rare, IME. Frequently these engines run rich due to improper mixture or over-choking, and if gas soaks the plugs they look black and wet.

A worn out engine turns a lot more easily than a newer engine. A trick is to push down on the taop of the fanbelt between the waterpump and alt/generator while turning the pulleys. Gets more grip.
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MPergiel, Elmhurst, IL '74 145e T-5 'Orange Alert'

And an engine that *can* soak the plugs with oil is going to leave quite a smoke trail.
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I'm JohnMc, and I approved this message.

From Chilton Repair Manual, Volvo, '70 - '89....

"Sparkplug Diagnosis...Oil Deposits...Appearance: The firing end of the plug is covered with a wet, oily coating. Cause: The problem is poor oil control. On high mileage engines, oil is leaking past the rings or valve guides into the combustion chamber. A common cause is also a plugged PCV valve, and a ruptured fuel pump diaphragm can also cause this condition. Oil fouled plugs such as these [pictured] are often found in new or recently overhauled engines, before normal oil control is achieved, and can be cleaned and reinstalled. Reccomendation: A hotter spark plug may temporarily relieve the problem, but the engine is probably in need of work."

pray its not the rings. of course, there are many factors not mentioned that are importaint to decifering what is going on. and btw, you can't usually turn the crankshaft with just the fan belt, unless you take the sparkplugs out or something first. If you could, it would probably mean really poor compression.
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-Ben- '71 142S (parts), '71 144S, '74 164E

Nothing you've described sounds like a real cue to rebuild the engine.

Oily plugs - does it burn enough oil to see it coming out the tailpipe? Do you have to add a qurt more oftern than every 400(ish) miles? Does it just leak oil and not burn it? In general terms, oily smoke out the tailpipe under power is more likely work rings, but oil smoke out the tailipe only on decceleration is likely just valve stem seals.

Turning the engine by the fan often results in a slipping belt - there is just a fair amount of friction inside the engine (all four pistons sliding the rings up and down) and the belt isn't meant to handle that. If it was tight enough to turn the motor with it it would probably wear out the water pump bearings quickly.

Rough idle can be any number of things - maladjusted carbs, loose/tight vavles, etc. Before you get into things like leaking valves, worn out rings, etc.
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I'm JohnMc, and I approved this message.