smoking oil, but good compression #'s

charofire

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Quick question for those who have personally experienced this situation: my friends 2800 coupe, after swapping what we thought was a good motor, has oil smoking out the tail pipe. I talked with 2 of the best authorities on these situations, Terry and Don, and both of them agree that it is odd to have good compression numbers (155-165), and smoke still coming out. The motor has now run for 2.5 hours. The oil rings may not be sealing. This engine apparently sat for many years. So far the plan is to soak the pistons in carb cleaner or atf for a few days. Any other suggestions worth pursuing, please let me know.
 

Lotuss7

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Duane...possibly really good call.

I have a 1967 TR4 which has a vacuum hose connection between the Strombergs and the intake manifold which feeds cylinders 2/3. Those cylinders were running a bit rich compared to 1/4 so I thought, heck eliminate the vacuum hose.

Didn't realize TR had by sealing the block needed to put it under negative pressure. Fired it up and drove it around the block. Big smoke and pushed oil past the seal at the crank at an alarming rate.

Hooked the vacuum line back up and all was well (2/3 still run richer however)

Crank pressure may be it!
 

Mike Goble

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Put the right weight oil in the engine and run it. My 3.5L motor smoked a bit when I first put it in, but after three years and many thousands of miles it doesn't smoke anymore.
 

jvrenaudon

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smoking engine

Charofire,

I had exactly the same experience this year with a recently-acquired CSI which had stood for nearly 10 years without any attention whatsoever. I was very hesitant about starting it and unable to remove the sump-plug (rounded off). In the event, I checked the compressions and they read 125,150,150,150,155,150. I started the engine and clouds of blue smoke issued from the exhaust. With time this reduced but still there was still a worrying quantity of blue smoke. However, over the last few months of just starting the car and moving it around on my drive I have noticed that the blue smoke has completely disappeared. The compression readings now read 145,155,155,155,160,150 using the same meter as before. My guess is that the oil scraper-rings were gummed up and that repeated starting, running, cooling has freed them. I must get around to freeing the sump-plug, though. John.
 

charofire

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Lotuss, on a coupe with Zenith's, what vacuum lines do you think my friend would be looking for to confirm?



Duane...possibly really good call.

I have a 1967 TR4 which has a vacuum hose connection between the Strombergs and the intake manifold which feeds cylinders 2/3. Those cylinders were running a bit rich compared to 1/4 so I thought, heck eliminate the vacuum hose.

Didn't realize TR had by sealing the block needed to put it under negative pressure. Fired it up and drove it around the block. Big smoke and pushed oil past the seal at the crank at an alarming rate.

Hooked the vacuum line back up and all was well (2/3 still run richer however)

Crank pressure may be it!
 

jmackro

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What about oil entering past the valve stem seals? Even if your oil rings are working 100%, valve seals are another potential point of oil entry into the combustion chamber. And you could still have terrific compression with worn/leaking valve stem seals (of course, you could still have terrific compression with worn/leaking oil rings, as long as the compression rings were OK - but usually both types of rings wear at about the same rate).

As others advise, I'd run it for a few hundred miles before concluding that intervention is necessary.
 

Stevehose

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The pvc hose from the valve cover attaches to the air cleaner assembly. I've seen plenty of engine setups with this hose not venting to carb intake (including mine) with no issues so not sure this is your problem, likely the engine needs to be run like Mike and John said. But ya never know.

Lotuss, on a coupe with Zenith's, what vacuum lines do you think my friend would be looking for to confirm?
 
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