Oil burning - rings or valve guides?

[79PWagon]

I've got a '79 W200 that was used as a Brush Fire Truck before I got it. Originally it had a 318, but a 360 crate motor was swapped in by the fire department. The body only has 30,000 miles and the 360 engine, less than 10,000 miles. I've owned it for 2 years, and the first year I had no problems. Now it burns 1 - 2 quarts of oil for every tank of gas. Talking to people, 90% of them say it is my valve guides. But then 10% of them say it is rings. The people who say bad rings give these reasons as arguments: 360 engines only have 1 oil ring as compared to 2 on the original 318, 318 engines are made to take higher rpm's than the 360 -- and the truck has really high gearing, and 75 mph is pushing it. I believe that the fire department did run the engine hard, and I know that I've pushed the rpms in the 2 years I've had it. Compression on all cylinders was in the range of 95 - 110 lbs before I treated it with SeaFoam. After treatment compression averaged 115 - 130 lbs. Any thoughts on this?
Thanks

[pwdave]

oil burning

before getting too carryed away with this, change the pcv valve, it will do what you describe, and if it works you will save two or three dollars. dave

[Paul in MN]

Does the exhaust look like blue/grey smoke?

Can you smell burned oil in the exhaust?

Is the smoke most noticible at start-up, or is it constant all the time?

One to 2 quarts of oil per tankful is a lot of oil missing. Is there a possible leak, maybe valve cover gasket, or maybe even a rust pit through the oil pan. The oil pan on my 86 W250 360 rusted through in about 6 spots. I brazed it up. The metal seemed too thin to weld it.

If the seafoam increased the compression, then I suspect the rings have become stuck and the seafoam has helped loosen them up, maybe solving the excessive oil burn problem. If it has worked this well, I'd give it another dose at the next oil change.

At the age of this truck and engine, I'd suspect the little rubber umbrellas on the valve stems/valve guides have cracked and failed. They can be replaced without removing the heads. If this is the case, I'd suspect a high amount of oil is being burned at start-up, and it reduces fairly quickly as the engine warms up. Usually this does not lead to wet/oily spark plugs as they burn it off.

With the compression numbers you have given, I doubt there is any need to replace the rings, and single oil rings are quite sufficient for well over 100K miles of use.

With the 4.10 gears in my W250, it likes a speed of 55 mph, and would probably throw out a lot of oil at 75 (NO WAY would I drive mine at that speed with the sloppy steering that has been rebuilt many times). As a fire dept brush truck, yours may even have the 4.56 gears, especially if it was originally equipped with the 318.

Paul in MN

[DODGEBOYS]

rings or valve guides / its as easy as driving up and down a BIG hill / if it smokes go,in up its the rings / if it smokes com,in down its the valve guides

but l would check everything else first