[AT] cub / prime oil pump

[ken knierim]

The famed Merlin engine in the P-51 I helped rewire had an electric
pre-lube pump. I believe the German FW-190 had something similar on the
inverted V-12 Jumo; sometimes these things are necessary.

That said, there are at least 3 different general methods of handling
prelubrication or startup that I have seen.

1. crank the engine until you have oil pressure, then turn on the
ignition (seems to be the situation with some of my old tractors no
matter what I do to tune them up). Poor-man's "pre-lube".

2. Prime the pumps manually. I rarely do this unless the engine has been
sitting awhile. I have a special adapter I made for my drill to drive
the distributor shaft for when I do it though, because I pre-lube every
engine I rebuild.

3. Start the engine and let it idle until oil pressure comes up, then
increase power.

Most of us will use a combination of 1 & 3. I have done this and still
had troubles:

I drove from Phoenix to my hometown in Montana for Christmas. Not
thinking, I left the 30w "summer oil" in it for the trip. That time it
got cold... it was -56 degrees the morning I went to start the Blazer.
It barely started but I got it going. After a few minutes of idling I
realized that I still didn't have oil pressure... it came up but REAL
SLOWLY. From then on I had rattle in the bottom end of the engine until
I replaced it (wanted more power than the old 305 could muster anyway).
Since then I have switched to Mobil 1; it doesn't seem to turn to tar
when the weather gets cold.

It's also been my experience on engines that while you may have gage
pressure, you still don't have flow out to all the bearings for some
time, many times 10-15 seconds after startup (watch the oil flow when
adjusting rocker arms). While there will be oil stored in the bearings
in most cases (more or less depending on wear, sit time, etc), engine
life is considerably enhanced by starting and idling for a bit before
putting it into gear. The rebuilt engine I have in a carbureted Camaro
has been driven HARD for 200K miles since a rebuild and it has no odd
knocks, rattles, etc. Smart start-up procedures and regular maintenance
go a long way toward keeping this old iron running.

Ken

On Thu, 2005-06-09 at 15:39, K7jdj at aol.com wrote:
> In a message dated 6/9/05 12:50:30 PM Pacific Daylight Time, 
> DAVIESW739 at aol.com writes:
> 
> I DID lose a set of bearings in an engine 
> that  failed to prime after setting all winter.
> 
> 
> Many larger commercial engines have built in pre lub pumps.  Some even have 
> electric pumps that are controlled by timers that pump lub oil through the 
> engine when it is not running.  I know of a case where the pumps were wired wrong 
> (3 phase) and the pumps sucked oil instead of pumping oil and you and your 
> fellow tax payers paid a lot of tax dollars to repair several of these engines.
> 
> Sometimes if one of my engines is slow to start after sitting idle for a 
> period of time I am glad.  I always pull the coil wire or diesel solenoid wire if 
> an engine has not been run for several months.  Crank until I've got oil 
> pressure showing and this is the recommend procedure in several shop manuals.
> 
> Gary
> Renton, WA.
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