My 225 in my 72 Duster is smoking.At first it was only at acceleration,but now it blows blue smoke at idle.How can I tell if its bad rings or bad valve seals? I pulled the plugs out,only 1 is oil fouled.I disconnected the spark plug wire from that cylinder,fired the car up and it still smoked.So I let the car warm up a bit,pulled the plugs out to do a compression check.Heres the results.Note,I didnt do the wet test,which I will do tomorrow

cylinder psi
1 110
2 110
3 110
4 130(this is the cylinder with the oil fouled plug)
5 110
6 110

Im pretty sure 110 is pretty low but need some opinions.Is this bad rings or valve seals?Ill squirt oil in the cylinders tomorrow for the wet test.

I've had really horrendous rings in a few slants, for instance a two engines had all the top rings broken, and none smoked at idle. It's likely that if the valve stem seals have never been replaced that the seals are not intact. It's also highly likely all the exhaust guides are well worn and probably the intake guides as well. The compression is a bit low, but not awful.

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Joshua

I just ran a dry compression test on my '70 with 105K mi and they were 120 across the board. I don't have a problem, I was just changing plugs and curious what my compression was. When you ran the comp test, did you have all the plugs out and the throttle plate blocked open? Re: smoke, my experience has been bad valve seals/ worn guides suck oil at idle when vacuum is the highest. You will then get a big puff when you accelerate away from the stop. Also watch smoke on decel. Valve seals also cause smoke when the engine is first started after sitting. Broken rings are usually accompanied by lots of oil consumption, like a quart every 300 miles. Your #3 may be high because of the oil helping ring seal, or it may be carbon deposits on top of the piston increasing compression.

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NO WHINING and NO EXCUSES!

thanks everyone.Actually,it hasnt consumed much oil at all.I noticed while driving ,i will look in my rear view and there will not be any smoke and it does smoke at deceleration.I did have all the plugs out and throttle open wide while doing the compression test.

Sounds like valve guides and seals. My test is to decelerate with closed throttle from 60 to 35 mph and then tromp down on the accelerator. If I get a lot of exhaust smoke, I'm replacing the valve seals.

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You can't fix stupid. - Ron White

Hello brother, Now, I'm reading the Haynes and next:

maximum compression; 100 psi
Maximum compression variation between cylinders; 25 psi

I think the valve seal.

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That consume your mind, that's controlling your life

Thanks everyone.This week i am going to replace the valve seals and see what happens.Im going to use an air compressor and do the old air in the cylinder so the valves dont fall in.Ive always wanted to try this and Ill keep you all posted on how this goes and hopefully take pics of the condition of the seals.

did that help your problem ????? or do you still have to do a valve lash because that is what i was told .