On Sat, 4 Jul 2009 22:00:05 +0200, "Steve Lusardi"
wrote:

Years ago when Evinrude and Mercury were promoting the V4 and their swirl
scavenged 3 and 6 cyl motors, I made a fortune rebuilding these engines for
the USMC, which all suffered from Marines using too much oil in the fuel. I
have also fried Corvette small block motors which suffered intake manifold
leaks on the bottom port surfaces sucking oil vapor from the lifter valley,
as well as Opel fours that lost oil control rings on the German Autobahn. At
partial throttle slight power loss and some pinging results. At full
throttle, parts melt..
Steve

How about some definitive numbers here. You say that the engines were
failing due to excessive oil in the premix - how much was too much?

Your experience seems very much at odds with my own as we had a slue
of Mercury six cylinder inline engines, in Iran Jaya, that were
seizing and the solution prior to my taking over as marine maintenance
was to add oil and add oil and add oil.
(the actual cause was weak fuel pumps which caused the top carb to run
lean).

I've seen detroit diesels "run away" and literally run on lube oil
from failed blower seals with no detonation problems. If too much oil
causes detonation then these engines certainly should have detonated
as they were running on straight lube oil.

Another problem I have with your assertion is that extra heavy oil
mixes - double the amount of oil, or more - usually resulted in the
engines running cooler then normal due to very poor combustion of the
high oil content mixes.

The small block chevies I've seen suck oil from the intake manifold
all ran with less power and smoked a lot but with no damage to pistons
from detonation.

In fact the only detonation damage I have ever seen was always traced
back to a lean mixture or too high supercharger pressure for the RPM.

By the way, in the early days of Yamaha racing the road racers had
problems with the engines seizing when you rolled the throttle back at
the end of a long straight. High engine temperature from the long full
throttle run combined with a sudden reduction in lube oil from the
closed throttle valve. (It made the drivers rather unhappy when the
rear wheel stopped turning at over 100 MPH). The immediate solution
was "ADD OIL" to the premix. It didn't cause detonation.

Even model airplane engines would sometime detonate - always from a
lean mixture.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)