[V8] Engine rebuild options
QSHIPQ at aol.com
QSHIPQ at aol.com
Wed Aug 27 07:49:25 PDT 2008
I rebuilt the heads on Ingo's 5spd car, and that didn't help either (maybe
70k at the time). I'm pretty convinced this oil sloshing is the main culprit.
My ex rarely stabs the pedal hard, and her oil PT oil consumption is nil.
Oil in combustion is a bad thing, since oil doesn't burn it really creates
hot spots (like at piston rings)... Add in a lot of timing advance it gets
worse. Add in the MAF doesn't like to be coated in oil either, you have a bad
fuel mixture during and after your run to boot. This can take out a motor
fairly quickly after a rebuild.
IME, the manual cars really slosh that oil, as to cars with suspension mods.
The AAN 20vt motor has the same sloshing problem. I really think that Audi
just didn't take the time in the 1980'2 and 1990's to address this design
correctly. The best place for PCV is dead center in the head. This avoids
sloshing front or rear mounted vent ports.
I also suspect that the cylinder walls (however they are constructed) don't
take well to all this abuse either.
HTH and my .02
In a message dated 8/27/2008 7:01:02 A.M. Central Daylight Time,
tonyandlillie1 at earthlink.net writes:
I do know of two that have rebuilt heads, and it didn't help. And mine,
which smokes pretty badly on long deceleration, doesn't burn anything
appreciably. BTW, that shows it's the heads, not the rings. Generally, smoke
on acceleration is rings, smoke on decel or at idle is the valve
However, I think there's something to Scott's theory about venting the heads
at the back. I guess if every acceleration is a hard one, pushing the oil
inot the venting system could lead to a problem.
That is pretty bad oil consumption on those ABH's. Just out of curiosity, is
it worse on manual transmission models? That seems to be one thing I see
here. And, that would also support the venting theory, as they have the
ability to accelerate much harder than the automatic models.
> well, the PT engines may also take more oil in the years (I talk about 1
> or 1,5 litres on 1000 km) but it usually helps to overhaul the heads
> (whereby mainly the valve stem seal is worn out)
> and it lowers oil consumption quite reliably and significantly. Doing the
> same on an ABH (and we're talking about amounts >3l/1000km, which we had
> on dozens, if not hundred machines in the forum over the years, not
> directly connected to the mileage) usually doesn't help a lot - the
> consumption remains, whereby the compression is perfect. The assumption
> that the reason for this are problems with the cylinder coating is a
> consequence - whereas somebody came up with the NiKaSil theory (stated as
> a fact, sincerely). So if it's not about NiKaSil, I wonder what's the
> reason and why the ABH, mainly the older ones, take significantly more oil
> than the PTs. There has to be a reason.
> If it's about overheating, what I personally experienced also (I had once
> an early '92 ABH with 240tkm on the engine and it significantly raised the
> oil consumption (well, from 1,5 to 2,5 or even more) after it overheated
> once due to a fluid leakage in mid summer) but didn't interconnect at that
> time, what engine parts are impacted by the overheating and how can it be
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