I had a 68 400 engine rebuilt. I have a problem with it smoking (oil) from the right side exhaust and sometimes it switches to the left side. This happens after it warms up and is prevelent when stopping and starting off. The engine builder has checked the compression and did a leak down test. All looks good there. He changed the intake gasket twice using a HP gasket the last time. He also changed the valve seals again in case they were defective. Still smokes. I did swap out the original carb for a eldlebrock and had to use a spacer. Could it be that there is too much vacuum with this and it is sucking oil out the PCV valve? I also read on another post of plugged oil return holes on the heads. It just seams strange that it switches from side to side as you corner and drive straight. I just had the original carb rebuilt and plan on istalling it. I may also replace the PCV valve again in case it is defective. I am also using an aftermarket breather. Should I hook up the original breather?
Does anyone have any other ideas? this is bumming me out

 

Its not sucking tranny fluid up the modulator vaccuum line is it?

 

No, That was checked out also. It may be worth a second look though

 

How do the spark plugs look...signs of fouling?...all the same color?

 

Are the valve covers baffled in the PCV/ breather area? If not, it could be sucking oil thru the PCV. A high volume oil pump will aggravate this condition since so much oil ends up in the rocker arm area. If valve seals are marginal or drainbacks are plugged, even more so, but a recent rebuild shouldn't have plugged drainbacks and you mentioned the valve seals have been replaced.

Were the heads milled at all? If they were and the intake was not milled to match, the intake to head seal may be open enough that high vacuum is sucking oil up the lifter valley and into the intake ports. This would show as oil smoke on deceleration or under steady cruise, similar to worn valve guides

Last 455 I built did this exact thing using an older Offenhauser Dual-Port that in retrospect, should have been milled and trued to the heads. Sometimes it smoked out the left bank, sometimes out the right. Sometimes it would blow out a quart of oil in 200 miles, sometimes I'd get a 1000 out of a quart. But that engine made some power...

Last, what weight oil are you using? If it's thinned out, it could easily get past rings and seals and cause this.

 

You bring up some interesting points. Not sure if the heads were milled but I don't think they were. I will double check. I do not remember seeing baffles on the valve covers. I do have another set on my old engine. I will check this out.
Thanks for the info.
Gary

 

The valve covers have the baffles and the PCV valve is working although there is a slight bit of oil in it. I had the Trans modulator valve replaced when I changed the leaky pan. The problem happens after the engine has warmed up. It is find when cold. I will double check the oil as the engine mechanic believed in using some type of oil for break in that is used in desil engines. It may be too thin. If so I will try changing it to a thicker oil. Thanks for your help,
Gary

 

Ok, I found out the heads were milled .010. What should i have the intake milled to? Is there a formular for this? I wouldn't think .010 would make a huge difference but I'm not an expert on this and it isn't out of the question that the heads may have been milled before since I bought them used. The engine builder said that there were no markings indicating previous milling.
Thanks for your help
Gary

 

Maybee, som of the second piston rings was put in upside down? It has happend before. That would put up a lot of oil inte combustion chamber.

Regards
Stanley