The Stovebolt Site Forums The Shop Area Engine Shop Blue smoke at start-up and letting off throttle.

Started my 1949 1/2 ton with a 216 cu.in engine after sitting for about two years. Sprayed MMO in the spark plug holes before letting it sit. Turned the engine by hand before starting and it turned easily. Started it up, set the timing at a total of 8 degrees, set the carburetor mixture screw at 3/4 turn from stop and set the idle a 475 RPM with tachometer. I have 21 hg vacuum at idle off the intake port and the needle is steady. Compression #1 105, #2 108, #3 102 #4 105, #5 107, #6 95. Valves have been adjusted as specified by the FSM. Noticed I have blue smoke from the tailpipe at start-up and when I let off the throttle from about 2000 rpm. Flushed cooling system. New hoses new 4lb.radiator cap and new thermostat. Temperature stays at 180-185 idling in place for over 20 minutes. The engine did not smoke before I let it sit. Thinking I may need to replace the valve seals? Umbrella seals or "O" ring seals? Any ideas as to why I now have blue smoke from the tail pipe?

Tim

Hy fixit1958, what you are describing is typical with worn valve guides and/or bad valve seals or both, hope that helps.

Blue smoke usually means valve guides are seals. Its possible the seals dried out over time and letting some oil slip by the valves.....question, does it do it continually, or clear up at some point? You may have a couple stuck rings. I'd drive it a while before doing anything major. Its time consuming but a set or valve seals would be my first stab at it. Others may have better opinons/ideas.

Tim, I may be down your way in a week or two at Shallotte. Maybe get together for lunch one day.

If I had worn valve guides wouldn't the vacuum gauge be vibrating? Stuck rings? What would be the best way to unstick the rings? Valve seals? Umbrella seals or "O" rings?

Alvin, let me know when you're coming to Shallotte and we'll see if our schedules mesh.

Tim

worn valve guides will let hot oil past when you shut the engine down without making your vacuum gauge flutter. As noted above, I would drive a tank of gas or two through it and see if things settle down. You can run a bit of MMO in the gas to help unstick rings if that is an issue.

I wasn't aware that a '49 had valve guide seals.

Tiny... http://www.oldchevytrucks.com/cart/product.asp?prodid=ME5521&i=10455|||||

Its amazing what a "seal job" did on my old 46 I once had that had set in a field for a year or two.

I know they're available now. My '38 doesn't have them and never did. I don't know when they were put on at the factory but I thought it was later than '49. I could be wrong, often am, just ask my wife.

I would use some engine flush clean things out. then with some new oil drive it a little while and see if things loosen up and work better. Seafoam in the oil may help as well. Two years is a long time to sit, run it some and give it a chance to work things loose.

Blue smoke, particularly on startup., is a sign of worn valve guides. Seals will be a temporary fix, but once a valve starts wobbling around in a guide, it will wear out a seal in a hurry. The "positive" guide seal that grips the guide and the valve stem will do a better job of oil control than an umbrella seal or an O ring. Some positive seals need a machined spot on the OD of the valve guide, while others are just a snug slip fit over the machined guide. Perfect Circle makes both types, but you're going to need to find a parts man who knows how to read a size chart, and some good measurements of the guide and the valve stem to get the right part. Nose-picker computer jockeys at the big box do-it-yourself parts stores need not apply!
Jerry