I have an 89 van 351 /C6. with either 93k or 193k on the odometer. It uses (one way or another) about a qt of oil/600mi. From reading here and elsewhere I believe Ford claims 1 qt / 700mi is acceptable. But I can smell oil in the exhaust and see grey smoke, especially on cold starts (I've smelled the exahaust at that time, and it's definietly oil...).

It runs well, but unfortunately I'm facing a smog test in Ca., so I've had to investigate this further. There are several things not right with the engine and I've been slowly patching it back together after the ravages of United Airlines fleet service (I've checked the plugs, PCV, air system, working on the EGR, Cat's bad, coolant sensor needs to be checked more closely...). My apologies to anybody connected to United, but when I found they had installed the wrong fan and it was blowing OUT, that pretty much set my opinions.

But the main thing is, where is the oil getting into the cylinders, cuz that will tell just how much grief I'm in for... I doubt even a new cat will eliminate all those HCs as it stands now.

Can somebody in the know tell me what compression to expect from a moderately healthy set of rings. The compression is 152 to 158 all around with the engine warmish (took about 30 minutes to get all the last plugs out) ; I checked one cylinder with oil and the compression rose to 185. Does that mean I get to blame the valve stems, or is that low enough to indicate ring problems?

Thanks for any thoughts.

Rufus

 

It's probably due for a complete re-build. A quart every 600 miles (assuming it's burned and not leaked) is terrible. 193,000 miles is way past the TBO. If it burns oil mostly when it's first started, then it does indicate the rings. As it warms up the rings will expand reducing the end gap and decreasing oil consumption. Additives like Slick 50, Z max, Duralube ..ect.. can and do cause premature ring wear, particularly chrome moly rings. I know this is the case from oil analylis of aircraft motors. The valve guides and seals could also be allowing oil by. In my experiance the valve guides need overhauled before the rings. It's probably both heads and rings. Anyway a leak down test dry and wet will tell you.

 

I would think oil at startup would most likely be from the valve guides/seals, but just those probably wouldn't allow oil by at the rate of 1 quart every 600 miles. Also check the pcv system for proper operation, but I agree, it's likely time for a rebuild.

 

Thanks for the replies. Sorry to hear them. <g>

The engine does _leak_ oil, but it most certainly burns too much. I guess I'll work up a leak down test and see where the noise comes from.

Anybody have opinions about where's a good place to get a good crate engine? I'm in kinda bind time-wise here, and that may be the quickest fix. Used engines worry me some, I guess I'll look there too.

Rufus