Oil burning after head rebuild (1 Viewer)

[vtcruiser60]

Should I expect to burn oil after a headjob?

I had the head rebuilt on my 84fj60 in late summer and am now experiencing some rather strong oil burning. I am down about 1 quart every 500 miles. I don't notice any blue smoke or drips, so I figure it is burning. When the head was off, the mechanic assured me that the lower block looked fine. Since the headjob the head bolts have been tightened, timing adjusted, and valve clearances readjusted. Idle is fine.

I read on sor.com that one could expect to burn oil after a headjob. But I keep thinking that I should have pushed further into the cylinders and had the full job done.

What is the relationship, if any, between oil burning and the headjob?

 

[Rice]

The strongest (not only) connection between heads and oil is the valve guides/seals. Question ... did the mechanic replace valves and put them in the old guides or were the guides also worked? Is there any blue smoke at engine start up after it's been sitting a while?

 

[vtcruiser60]

Hey Rice,

Valve seals were replaced, but I believe the guides were not. All the valves were ok. No blue smoke at start up or otherwise. I appreciate your reply.

 

[theo]

I agree with Rice. You know the song Fifty Ways to Leave Your Lover? 50 ways to rebuild a head too.

Something else you can hear in every machine shop: The increased compression from new, properly working valves can cause the rings to lose some of their seat and blowby can increase. The risk increases with mileage. Other possible "reactions" are increase wear on main bearings, rod bearings, cylinders, pistons, etc.

 

[vtcruiser60]

What should I do? Would a leak down test help diagnose the problem? I am wondering if I can live with this level of oil consumption or if I should dig a bit deeper and try and solve the problem. I don't want to ignore it and then have a valve or head crack down the road.

 

[wesintl]

do a wet and dry compression check to see. Dry will let you know if it's going past the rings and wet will let you know if it's going past the valves. I suspect if the machine shop didn't replace the valve seats they were ok. If not you have a lame machinist. I suspect it's going past the rings from what you said so far and what theo said. you can get rings and bearings from pac lift and do the bottom end... hth

 

[theo]

[quote author=vtcruiser60 link=board=1;threadid=9657;start=msg84900#msg84900 date=1073333448]
What should I do? Would a leak down test help diagnose the problem? I am wondering if I can live with this level of oil consumption or if I should dig a bit deeper and try and solve the problem. I don't want to ignore it and then have a valve or head crack down the road.[/quote]

The compression checks are a good idea. If you have one "dead" cylinder you have problems. If compression is even across all 6 you have less to worry about. (Just a note, the dry test can't differentiate between rings and valves, but the wet test (a squirt of oil in the spark plug hole) can eliminate rings.)

I guess if you got lots of carbon deposit buildup on the valve faces and seats so they began leaking badly they would start heating up and eventually maybe break. Unusual, uneven heat buildup could warp or crack the head. But before that happens you should get noticeable smoke that gets worse over time. You should get other subtle indicators too, like rough idle, decreasing power, etc.

If you can live with the oil consumption you have, and it doesn't get worse, I would be tempted to drive it until you have the time and money and gumption to rebuild the bottom. The head should be fine for a long time and only need minor cleaning; you shouldn't have to rebuild it again.

You could do a poor man's short block: pull the head back off, pull the pan and oil pump and crankshaft, push the pistons out, hone the cylinders, rering it, and put it back together. But it's risky. And it always seems like the farther you go the more it needs, until you're better off doing a complete, competent job all at once. That's why I say wait and do it right once.