The Stovebolt Site Forums The Shop Area Engine Shop Blue smoke

I had my 250 rebuilt a little over a year ago and I only have maybe 10,000 miles on it. When you let up on the gas and you are going down hill blue smoke starts to come out and then when you start going again it stops. I thought maybe the PVC valve was sucking oil in the intake. I changed it and that didn't work but I still thought that had to be the problem and I finally just took the thing out and drove it that way and the problem is still there. Sometimes it doesn't do it. Here is what they did to my motor when it was rebuilt. They change all the valves in the head so it would burn unleaded. They change a sleeve that was cracked in the block and put in all new pistons and of course change the usual things. Please any suggestions and Ideas

climberman,

Good move on taking the PCV out of the loop. The scenario you describe is typically a valve guide problem. You state the rebuild included head work. I wonder if the shop that did this checked the wear on the guides, replaced the guides or knurled the guides. I won't cast dispersions, but a good automotive machine shop would have surely addressed this during a head rebuild.

I don't know what a 250 uses for valve stem seals but this would be an area to keep in mind too. Talk to the machine shop.

Stuart

What you are describing here is the same thing I was thinking I had a ford motor do that many years ago and it was the guides.

Anyway what you are saying is that because the smoke only comes out when I let up on the gas it has to be a problem with the head is that right? The lower part of the engine is fine is that right?

climberman,

Generally speaking, ring/piston issues develop smoke under load, when you are accelerating. Under no throttle, high vacuum conditions, the engine will pull oil through the guides into the engine. This usually shows up when you coast down a steep hill under no throttle, then hit the gas at the bottom and the smoke pours out.

Your scenario sounds like top end problems, not ring problems.

Stuart

Thanks Stuart - The mechanic will be calling the machine shop Monday I hope he will still honor the warranty but it has been about two months longer then a year. Of course if it is something he didn't do right he should take care of it but you never know.