Spark plug issue

[bfd378]

I have a 350ci tbi to carb it's been running a bit rough. Decided to pull plugs to relash valves. When I did the 1, 3, 5, 7 plugs were oil burned indicating I had a oil issue, bad rings ect. Question is Iv never saw rings on one side of the motor be out like that. Normally it's one or 2. The passenger side looked fine. Any suggestion on what could have causes this? Motor was rebuilt by previous owner of truck and is .060 over. Thanks

 

[rich weyand]

I would think there would be a common cause, like the PO forgot the oil seals on the driver's side, or there is a bad gasket fit on the driver's side.

In the meantime, the Autolite 26 plugs are the cross-reference to the AC Delco R45TS, and are less susceptible to oil fouling.

 

[chengny]

Are you having to add a ton of oil to maintain the dipstick level?


If not, I would not suspect oil control rings (especially as you say - only on one side). Spark plugs generally only become oil fouled when engine oil consumption is real high - like 1-2 quarts per week.

You're sure it's oil fouling and not carbon? Could the the black deposits be due to running an overly rich fuel/air ratio on that side?

If you are sure it is an oil coating issue, then X2 Rich's thoughts on the improper installation of valve stem seals. Does it blow blue from the tail pipe at cold start?

Is your PCV system fully functional? Excessive crankcase pressure due to lack of ventilation can force oil vapor past even fairly tight rings.

 

[rich weyand]

Is your PCV system fully functional? Excessive crankcase pressure due to lack of ventilation can force oil vapor past even fairly tight rings.

Ooo. Didn't think of that one. Replacing the PCV valve is a normal part of a tuneup. Ever change it? They get clogged up and stick. And they will affect the PCV valve side more than the vented side, which can vent out. Which side is the PCV valve on? It's the doohickey in the valve cover with the hose to the front of the carb. They're like two bucks at absolutely any parts store. Just replace it so you know that isn't it.

You can also test to see if it's stuck by pulling it out and shaking it up and down. If it rattles, it's not stuck. There is a piston in there that gets pulled up by vacuum to vent the crankcase. They get oil vapor film on them, and if the truck sits, they can stick. You might also be able to clean it out if it's stuck and you don't have a chance to get to the parts store. Just blow some WD-40 through it and shake it until it rattles.

 

[bfd378]

I pulled the head Found a few things. Piston # 1 had crack, valves were in need of cleaning an one head is a 191 other is 193

 

[bfd378]

Feel it's been like this for a while. This is a play truck so I figure I will slap it back together and go till she blows

 

[highdesertrange]

imho .060 over is way to much for a dependable 350. you will have problems until you replace it. obviously those aren't forged pistons. highdesertranger

 

[chengny]

GM gives a max overbore spec of .030".

I think that it is sound advice. Here is what can possibly result when bored .060 over:

You must be registered for see images attach