Today's Message Index:
----------------------
1. 07:12 AM - Re: Engine break-in (Gary Casey)
2. 12:41 PM - Re: Re: Engine break-in (Archie)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Engine break-in |
--> Engines-List message posted by: "Gary Casey" <glcasey@adelphia.net>
<<The reasons for this procedure are obvious, and is utilized whether a
stock
or racing engine. On the racing engines, there is no break-in.
They are ready to "kill" in about 5minutes running.
Archie>>
But how does the engine know that it's a "race" engine and not a "regular"
engine?
This whole break-in procedure has always been puzzling to me. As I
understand it, there are two areas in the engine that usually require a
"break-in": In other words the final machining process are accomplished
with the engine running. One is the cam lobes and in this case low rpm
running is bad as that is when there is minimal splash and maximum contact
stress at the lobe tips. During cranking is there sufficient splash from
the rod bearing journals to lube the cam lobes(Lycoming)? If not, the
initial recommended cranking for 1 minute might be damaging. Cam lobes
should be assembled with an "EP" type grease that will protect them for some
time, but I'm not sure how long. As I understand it the reason for breaking
in the rings and bores is that you need the peaks of the roughness worn off
to get a smooth surface, but one that still has oil-retention grooves or
pockets. Running at high load increases the pressure of the ring against
the bore, but only at the top of the cylinder - what about the bottom of
bore; doesn't it need a break-in just as much as the top? "Glazing" seems
to be when the cylinder is run hot enough to burn the oil, leaving a hard
varnish behind that prevents sealing. True? If so, this would be more
likely after first start-up than after "break-in" as the cylinders run
hotter initially. Anecdote: I'm afraid I did that to a well-worn set of
chrome cylinders when I climbed out from a high-altitude airport on a
100-degree day. The oil temp went to the red-line (245?) and I was unable
to increase airspeed or decrease rpm for about 5 minutes. After that the
oil consumption went from 4 to 2 hours/quart. We re-ringed and honed the
cylinders and are now back at 4 hours/quart.
Most passenger car engines don't need a break-in schedule because the bore
finish is more controlled - so I've been told. When my plane is done it
looks like I will have to choose between paying for a dyno break-in or
accepting an incomplete break-in, as I doubt that the plane will fly within
a few minutes of first start-up.
Gary Casey
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Engine break-in |
--> Engines-List message posted by: "Archie" <archie97@earthlink.net>
> But how does the engine know that it's a "race" engine and not a "regular"
> engine?
The cylinder wall finishes are 800cork finish with no cross-hatching.
The rings are automotive style, and pre-lapped prior to assembly.
The rings are seated in less than five minutes this way.
(remembering this is against FAA procedures, but not against common sense)
> This whole break-in procedure has always been puzzling to me. As I
> understand it, there are two areas in the engine that usually require a
> "break-in": In other words the final machining process are accomplished
> with the engine running.
Indeed. That is due to the fact that the manufacturer's parts designs are
from the 30's
and that is the procedure utilized when incorporating that technology.
If these components were to be brought up to automotive standards, you would
not
have such elevated cylinder temp on initial startup and break-in.
Why scrape and grind, and contaminate the oil this way, when updating
everything
with precision parts and work eliminates these headaches?
Autos required break-ins up into the 50's.
< One is the cam lobes and in this case low rpm
> running is bad as that is when there is minimal splash and maximum contact
> stress at the lobe tips. During cranking is there sufficient splash from
> the rod bearing journals to lube the cam lobes(Lycoming)? If not, the
> initial recommended cranking for 1 minute might be damaging.
Negative. When cranking with the plugs out, there is no load on the
bearings,
and since the oil filter element is already saturated, there is essentially
no period in which
oil pressure is not there. The additional cranking will insure that every
air pocket
in the passages has been replaced with oil, so that when the engine is
"fired up"
everything is lubricated.
> Cam lobes
> should be assembled with an "EP" type grease that will protect them for
some
> time, but I'm not sure how long. As I understand it the reason for
breaking
> in the rings and bores is that you need the peaks of the roughness worn
off
> to get a smooth surface, but one that still has oil-retention grooves or
> pockets. Running at high load increases the pressure of the ring against
> the bore, but only at the top of the cylinder - what about the bottom of
> bore; doesn't it need a break-in just as much as the top? "Glazing" seems
> to be when the cylinder is run hot enough to burn the oil, leaving a hard
> varnish behind that prevents sealing. True? If so, this would be more
> likely after first start-up than after "break-in" as the cylinders run
> hotter initially. Anecdote: I'm afraid I did that to a well-worn set of
> chrome cylinders when I climbed out from a high-altitude airport on a
> 100-degree day. The oil temp went to the red-line (245?) and I was unable
> to increase airspeed or decrease rpm for about 5 minutes. After that the
> oil consumption went from 4 to 2 hours/quart. We re-ringed and honed the
> cylinders and are now back at 4 hours/quart.
>
> Most passenger car engines don't need a break-in schedule because the bore
> finish is more controlled - so I've been told. When my plane is done it
> looks like I will have to choose between paying for a dyno break-in or
> accepting an incomplete break-in, as I doubt that the plane will fly
within
> a few minutes of first start-up.
> Gary Casey
Too much here to comment on, you need to take in some of my seminars at OSH.
First, there is no "splash" from the crankshaft, it is merely throw off from
the rod bearings.
Perhaps it is time to write another magazine article.
This is not rocket science, just available technology utilization with
common sense.
I would be happy to address any questions, one at a time.
Archie Frangoudis
Archie's Racing Service
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|