In article <199506201448.IAA22440@triumph.cs.utah.edu>,
hal@gort.space.swri.edu wrote:
>
> After about 10 to 15
> minutes into the drive I noticed that the 6 started to blow some blue
> smoke (THIS IS BAD). It seemed to get worse as the day progressed
> (THIS IS VERY BAD).
> the oil pressure was a little
> above 50 when the car was idling and above 75 when at 3000RPM (THIS IS
> GOOD). Then I started to notice the smoke. A little at first, but
> more as I continued to drive. Also, the oil pressure started to drop
> so that by the time I stopped it was about 20 when the car idling and
> about 50 at 3000RPM (THIS IS VERRRY BAD).
Is it? As the oil heats up, the pressure will decrease. This is *perfectly*
normal, and nothing to worry about whatsoever. For an engine in good
shape, the oil pressure at 2000 rpm should be between 40 and 60 psi.
If your crankshaft has got a reasonable number of miles on it, I'd say the
numbers you are referring are perfectly OK, especially with a 10w/30
oil in summer. I'd agree that 10w/40 or rather 20w/50 probably is
better for summer driving, but I really cannot see what is wrong
with your oil pressure readings otherwise.
The only point about the oil pressure is that it shows that fresh
oil will be pumped to the bearings. 20 psi at idle and 50 psi when
running will be plenty for that task, and again -- nothing to worry
about. FYI, Mercedes Benz oil pressure instrument have such a low
full scale reading that they always register maximum, simply to avoid
all the "worried" questions.
Some people put in harder oil relief springs to increase the oil
pressure. This is plain silly. This will only waste power maintaining
the oil at too high a pressure, and wear the oil pump prematurely in
the process.
> The smoked was more evident
> when I was accelerating or engine breaking.
I'm pretty convinced that your blue smoke has nothing to do with
your oil pressure readings.
Since your top is newly rebuilt, you cannot overrule the possibility
that something wrong has been done with it.
Blue smoke with closed throttle and engine braking would suggest a
leak in the inlet valve guide. Due to the high vacuum, oil may be
sucked through the guide and burnt.
If the rings are bad, that will show up pretty well on a compression
test. Always test the compression with a hot engine (even though you'll
burn your fingers on the plugs :-). At the same time, check the
plugs.
> The only other weird
> thing that I noticed was that when I accelerated the oil pressure
> dropped for a second or two. I don't know if this is normal.
The oil level should be around the maximum mark, the minimum mark is
really a bit on the low side in my experience.
> I am hoping
> that one of you will tell me that the head is not torqued down enough.
That would normally cause white smoke, not blue, I'm afraid. And a loss
of coolant.
Egil
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Email: egilk@oslonett.no Voice: +47 22523641/92022780 Fax: +47 22525899
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