Diagnose these plugs

[arcturus]

Plugs removed from B20b. What's your diagnoses of the state of engine?

[blueosprey90]

Is this a quiz?

Hard to tell, but you're burning oil or running rich.

Since #1 looks OK, probably burning oil. But where is it coming from? rings? valves?

Any symptoms?

[arcturus]

Been "re ringed" recently. Most likely valves. Yes I like to run on the rich side.

[blueosprey90]

Did you break in your piston rings correctly? I've never done it for a Volvo engine, but had for the MGA several times. I run the engine at variable speeds between say 2,000 and 4,500 rpm and coast against the engine often by lifting. That creates a back pressure that helps seat the rings. I'm pretty aggressive with it and can get them seated in about 100 miles.

I'm assuming you have dual carbs. #1 and #2 should look the same if it is a carb adjustment problem. To me it looks like #1 is clean and #2 is sooty, as are #3 and #4.

You might be getting oil leaking down the valve stems. But that would be most apparent with a puff of smoke when you start the engine.

[Clan]

Originally Posted by arcturus

Plugs removed from B20b. What's your diagnoses of the state of engine?

They are not wet with oil just far too rich, unless you have been doing cold running at low speed . You cant do a reliable visual plug test unless you turn off the engine whilst still at speed and coast to a stop and take the plugs out ..

[dingov70]

I agree with Clan way way too rich a mixture .

When the engine has been for a long run , check them again & the ceramic nose should be almost the colour of a rich tea biscuit maybe as dark as a digestive biscuit ( a nice light brown ) . Strange colour comparisons , but an easy one to grasp (especially with a drink of tea ! )

Running the engine that rich will wash oil from the bores accelerating wear . It would be interesting to perform an emissions test just to see how far off the chart the mixture is

[arcturus]

Thanks all. I usually do lift pin test for mixture but that can sometimes be a bit iffy. I will try "leaning" by one flat.I also suspect valves and plan to have replacement head later in year with hardened seats.

[blueosprey90]

Take the dashpots off and with a Vernier caliper measure the distance between the top of the jet and the bridge.

When I first tuned my carbs, the rear carburetor was set at .135”, the front one at about .13”. I reset the jets on both carburetors to .10”. One flat seemed good for about .01”.

That adjustment eliminated a lot of fumes. But of course, I couldn't leave well enough alone and leaned the carbs out further, probably to .08" or .09”.

In March, in a delusional moment when I thought I might get the car on the road, I started up the engine and was getting a symptom in the carbs that sounded like a dog sneezing. So after I had the car running for half an hour or so, I did a plug check and my plugs looked far too lean.

So I need to re-adjust and will probably shoot for 0.10" or maybe 0.11" as my assumed sweet spot.

In the grand scheme of things, running rich is not beneficial.

[arcturus]

Did compression test this morning with hot engine. Results. Number 1 cylinder 9 psi. 2-3-4. 10 psi Any comments? Should i repeat with cold engine? B20b engine. 240000 km

[ksmi]

Originally Posted by arcturus

Did compression test this morning with hot engine. Results. Number 1 cylinder 9 psi. 2-3-4. 10 psi Any comments? Should i repeat with cold engine? B20b engine. 240000 km

Morning A, Are we talking bars here? Would be worth while doing a wet test,i.e. with some oil down the bores and spun over a few times before taking readings.

Regards from Sunny! Somerset,Keith.