Smoke on decelleration

[tylka]

I recently just purchased a 1980 911SC with a ROW 3.0L engine. The engine runs very well and strong but has a smoking issue on deceleration. The owner I purchased the car from was very honest and told me about the issue. He said he was driving the car one day and it starting smoking so he did a compression test with results of 160+ on all cylinders. His mechanic said it may need new valve stem seals. The car has been parked for around 2 years since the problem occurred because the owner was unsure of the problem and did not want to harm the motor. He must have started it on occasion because it does start up rather well. Any ideas if this could only be a head issue? If so I have seen a lot of good things written on Anchor Atlantic Enterprises on rebuilding heads. Thank you in advance.

[Flat6pac]

Usually, if you need valve stem seals, you need valve job to go with them.
Bruce

[porschetub]

is the oil consumption within factory specs,are the spark plugs showing oil fouling?
what oil are you running?

[tylka]

I have not checked the spark plugs since purchasing the car. The owner did say he was running Royal Purple oil made for aircooled motors.

[tharbert]

As Bruce pointed out, if seals are going, there's probably other head components that are out of tolerance. It you have to pull the heads to replace the seals, you might as well have them rebuilt. Along with seals wearing out, the guides get out of tolerance and heat transfer from stem to guide suffers and can eventually lead to burnt valves. BTW, I used Anchor Atlantic for my heads. They look great!

I too had smoke on deceleration. I was running 10-30 but I raised the viscosity to 20-50 (dino Castrol) based on something I'd read here and they were right. With the higher viscosity, it didn't smoke as badly. You may be able to get a few more miles before tear-down.

[porschetub]

Originally Posted by tylka

I have not checked the spark plugs since purchasing the car. The owner did say he was running Royal Purple oil made for aircooled motors.

Did read about issues with Royal Purple some time ago,think it was on here? not interested in an oil argument but have changed oil in many cars to other brands and cured consumption/smoking issues on otherwise good engines.
All my cars get oil changes after I buy them to brands that I know and have trusted in the past.
To me its all about what oil the car was using in the era it was made,had a friend put Mobil one in a freshly run-in 356b motor......it leaked everywhere and smoked,he went back to an old-school oil and all was good.......just saying.

Get those plugs out check them for deposits,you could also check the guides when setting the valve clearances.
I remember Bruce Anderson saying that not all these motors had valve guide issues and some went to huge mileages untouched.

[Josh D]

I developed a smoking and oil consumption issue out of the blue. Did the usual leak down tests, spark plug check, etc and everything was good. Pulled the heat exchangers and found #2 exhaust port was oily. Pulled valve cover and looked real close at the valve seal and it had come off the guide.

I bought the spring compressor tool and replaced the seal with a new teflon seal and all is good. While I had the exhaust off, I rotated the engine to get each valve off it's seat and pushed on the valve with a large screwdriver to check for play. All guides were tight, no play detected at all. The valve that I removed the spring on I was able to put apposing forces on both ends. No play at all. Tight as a drum.

Bottom line, valves seals can be a problem even if guides are tight.

[tylka]

When I purchased the car I was thinking the heads would most likely benefit from a rebuild. from what it sounds like and the symptoms I have, would it be safe to say the heads most likely need rebuilt? Thank you for the responses and help so far.

[porschetub]

Originally Posted by Josh D

I developed a smoking and oil consumption issue out of the blue. Did the usual leak down tests, spark plug check, etc and everything was good. Pulled the heat exchangers and found #2 exhaust port was oily. Pulled valve cover and looked real close at the valve seal and it had come off the guide.

I bought the spring compressor tool and replaced the seal with a new teflon seal and all is good. While I had the exhaust off, I rotated the engine to get each valve off it's seat and pushed on the valve with a large screwdriver to check for play. All guides were tight, no play detected at all. The valve that I removed the spring on I was able to put apposing forces on both ends. No play at all. Tight as a drum.

Bottom line, valves seals can be a problem even if guides are tight.

Josh great reply it appears the OP wants to race into a top rebuild without knowing exactly why he's in there,but we don't know the mileage of the motor and OP hasn't stated oil consumption....a can of worms really.