Oil loss can be mysterious. I'm trying to explain some suddenly
outrageous consuption myself, like 50 miles/quart. It's gotta be a leak
to lose that much, since there is no blue smoke at all, but I haven't
been able to find it--the paper on the garage floor is not any more
spotted than usual....
Blue smoke, attractive as it may be and helpful for holding down the
mosquito population, indicates that excess oil is getting into the
fuel/air mix.
You can check for worn rings, sort of, with a compression gauge and a
squirt can of oil. Check your compression figures for each cylinder and
record them. Then squirt a couple of tablespoons of oil into a cylinder
and do the compression test again. No change=rings were not leaking.
Worn rings can be replaced, but before you do it you would want to make
sure that the wear of the cylinders is within acceptable limits. If you
remove the head, you may find a ridge right at the top of the cyl, which
is just above where the top piston ring stops its upward travel. That
ridge is the size the cylinder was. Wear also takes place down the
cylinder, as the cyl can wear tapered, and can also wear oval. There are
acceptable amounts of this before boring is required. Oversize piston
rings are calculated and made to compensate for the larger bore diameter
from re-boring the engine, which is generally done in steps of .010. One
does not indiscriminately use oversize rings without doing some careful
measuring first....
If the valve guides are leaking, or the seals are worn, excess oil will
flow down the stems and into the cylinders. One approach is to remove
the rocker shaft assy, then wiggle the valve stems to see if they are
loose in the guides. If they are tight, you may need seals only, and it
is possible to replace them with the head on the engine.
For the impoverished student, this is a difficult area---trying to do
the right thing without the right amount of money. Try to soak up all
the advice you can get from your MG friends on this list before you get
the wrenches turning.
Bob
On Sun, 9 Nov 1997 18:35:19 -0600 (CST) Der schwarze Buccaneer
<js-allen@students.uiuc.edu> writes:
> I've got a '72 MGB that uses oil as if it were gas. I tried
>manipulating the smog control devices on my own, to no avail, hoping
>it
>would be a quick temporary fix. Now I'm left with two possibilities -
>
>the rings or valves (or both). I've got a Haynes manual, but it
>doesn't
>really explain how to tell which is the likely problem, or how to test
>
>them. I am thinking about pulling the head off and just seeing what
>it
>looks like in there, but I figured I'd see if anyone has anything
>helpful
>to say before I do. What do I look for with worn rings or valves?
> I'm thinking about trying to replace the valves, springs,
>etc.,
>with new parts, grind the valve seats with paste, and replace just the
>
>rings on the pistons. I've never tinkered with pistons before, so I
>know
>nothing. How do I determine if oversized rings are needed? Can I
>expect
>some improvement by changing just the rings without a full rebuild
>(and
>w/o new pistons), granted, I don't know what the pistons look like,
>but
>assuming they are not ruined? I'm not looking for 'like new,' at the
>moment, I just want it to get better _oil_ mileage until I can afford
>to
>fully rebuild the engine (or replace it with a cheaper to maintain
>American
>one).
>
>
>
>
> -Scott Allen
> js-allen@students.uiuc.edu
>
> "At dawn we will face the greatest test of our resolve. But I
>
>say this: though starving, hunger will not weaken us; though diseased,
>
>illness will not cripple us, and though weary, exhaustion will not
>claim
>us. We can fight knowing that all true Reiklanders will forevermore
>honour our valiant gesture of defiance, even though our bodies be left
>to
>feed the beasts of carrion.
>
> Mind you...we could always surrender." -Rick Priestly's Siege
>
>
>
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