Ford 289 with oil on plug threads

callbald

callbald

Senior Member
I need help on this one. I have a 64 Galaxie, with 289 engine that started missing. I pulling the plugs found oil on the threads but the ceramic electrodes were not fouled. I could not find any valve cover oil leak. I cleaned everything up, reset the plug gap and installed reusable valve cover gaskets.
Its now running smoothly, but don't know why the plug threads were oily. My guess is the problem could resurface.

Background:
This 289 engine has many unknowns because the former passed away. He rebuilt the engine using aluminum heads made by who knows and it has Autolite APP3923 plugs that have absolutely no Ford application and mostly applies to Nissan, Toyota and many more 1986-2018 non-Ford brand vehicles. The way the engine runs it feels like it has a mild cam and valve train setup.
 
I suppose the oil could be coming from the guides, what type of seals does it have. Maybe you can post a picture of the heads with a valve cover off, detail.
 
20190917_142418.jpg
As you can see any oil on the threads must come from the combustion chamber so the most likly source is the valve guides in my opinion next would be the rings. You could do a compression check but I suspect that the guide seals aren't up to snuff. The no name heads are leaning me this way.
 
I replaced the plugs 2500 miles ago. Compression is good 165-170 for 7 cylinders with the 8th at 160. The plug electrodes are a little black but not crudded with carbon and easly cleaned with with brake cleaner and nylon brush.
 
I'm still thinking valve stem seels. Quality of parts on those heads is not the best but there's no reason you can't put good parts on. You can change them with the heads on the car with air plumed to the cylinders through the sparkplug holes. But I'd be tempted to pull the heads and look at the valve job.
 
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