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Joetul(at)cox.net
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 Posted: Fri May 19, 2006 4:54 am Post subject: Need baffling help #3 |
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I had to have my engine rebuilt at 400 SMOH because the previous
assembler didn't use silk thread on the crankcase halves and it
developed an ever increasing oil leak.
Had the case overhauled and sent the cylinders out for overhaul. Shop
put it back together and runs great.
Only problem is CHT on #3 cylinder. In cruise it runs 365 but in climb
I can get it to 400 no problem.
Only way to keep it cooler is to throttle back lower the nose.
If I just nose over the temp keeps climbing. All other cylinders are
much cooler.
Before we removed the engine, there never was a CHT problem and the
baffles and seals are 2 years and 400 hours old.
Other than cylinder overhaul, what do I look for?
Is the tension of the wire on the cylinder wraps critical? (These are
tight).
Baffle mod maybe?
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FLYaDIVE(at)AOL.COM
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| Posted: Fri May 19, 2006 6:13 am Post subject: Need baffling help #3 |
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In a message dated 5/19/2006 8:55:06 AM Eastern Standard Time, Joetul(at)cox.ne=
t
writes:
I had to have my engine rebuilt at 400 SMOH because the previous
assembler didn't use silk thread on the crankcase halves and it
developed an ever increasing oil leak.
There are other methods of sealing the case halves other than JUST the silk
thread. Personally I feel the silk thread is a pass=E9 method of sealing.
My question would be: What type of oil are you using?
It has been reported that engines that have not shown any signs of leakage
tend to show leaks when Synthetic Oils are used.
Had the case overhauled and sent the cylinders out for overhaul. Shop
put it back together and runs great.
Only problem is CHT on #3 cylinder. In cruise it runs 365 but in climb
I can get it to 400 no problem.
Sounds like my Grandmother ... She would be alive to day if she wasn't dead.
Ya got to love the English language.
Really Joe; since the engine has been rebuilt, it sounds like it is going
through the break-in period. And #3 usually runs hotter than the rest.
Take a look in the archives on breaking in an engine. Basic rule: Don't
throttle back, add power and fly S&L. To this rule add, vary your RPM every=
15
minutes, enough to allow the cylinders to cool by something like 25 to 50 De=
g F.
This number is not etched in granite, what you are looking for is a cooling=
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flyv35b(at)ashcreekwirele
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| Posted: Fri May 19, 2006 7:17 am Post subject: Need baffling help #3 |
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| Quote: | I had to have my engine rebuilt at 400 SMOH because the previous
assembler didn't use silk thread on the crankcase halves and it
developed an ever increasing oil leak.
Had the case overhauled and sent the cylinders out for overhaul. Shop
put it back together and runs great.
Only problem is CHT on #3 cylinder. In cruise it runs 365 but in climb
I can get it to 400 no problem.
Only way to keep it cooler is to throttle back lower the nose.
If I just nose over the temp keeps climbing. All other cylinders are
much cooler.
|
How much cooler? It is normal for #3 or #4 to run hotter than the front
cylinders. Usually #3 and #4 are within about 10 F or so of each other.
365 in cruise is fine and 400 F in a climb is OK too. All of your cylinders
should be well broken in by 400 hrs, actually pretty well complete by 40
hrs. Do the lower spark plugs all look the same? Any signs of excess oil
consumption on #3. Excess blow-by past the rings will heat up the cylinder
and cause it to run hotter.
| Quote: | Before we removed the engine, there never was a CHT problem and the
baffles and seals are 2 years and 400 hours old.
Other than cylinder overhaul, what do I look for?
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Baffling that wasn't installed correctly. Holes at the rear of the cylinder
down around the pressure relief valve and in front of it and the base of the
cylinder. Flashing between the cylinder fins near the spark plug boss.
| Quote: | Is the tension of the wire on the cylinder wraps critical? (These are
tight).
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Yes, this is important. Also the cylinder wrap from the rear side should
not extent to far under and around the cylinder such that it comes close to
the tapped boss for the CHT probe. It may need to be trimmed back a bit, so
of to match the inner cylinder baffle between the two cylinders.
Cliff A&P/IA
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GrummanDude
Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA
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| Posted: Fri May 19, 2006 10:53 pm Post subject: Need baffling help #3 |
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Could you send some pictures? Send them to TeamGrumman(at)aol.com
My first thought is, "Wait until the rings break in."
Keep the baffles tight around the bottom.
Look at my web site, www.AuCountry.com
click on TeamGrumman
click on the button on the left that says, "Restoration ..."
Scan down until you get to baffles. There are a lot of pics on baffle
installations there.
Gary
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_________________
Gary
AuCountry Aviation
Home of Team Grumman |
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