Had this email in the archives from Oct. 14/99 - just copied and pasted
here.
Re lycoming 0-320 Lycoming engines manufactured before 1964 (1971 for 540
series) were of narrow deck design. These engines used cylinder base hold
down plates and internal-wrenching type cylinder based nuts. The narrow deck
design incorporated anchored through-studs that are of an earlier design and
created crankcase fretting problems. Anchor through-stud engines should not
operate past factory recommended TBO time's because of the possibility of
crankcase fretting. After these dates, lycoming engines became wide deck.
Wide deck engines have regular hex type cylinder base nuts and a thick
cylinder base flange approx. 3/8 thick. The thicker cylinder base flange
makes the wide deck engines slightly wider then the narrow deck engine. The
switch from narrow deck to wide deck did not chnage the model number of the
engine even though cylinders and crankcases are not interchangeable. Another
method you can use to distinguish narrow deck from wide deck is by the
engine serial number. If the serial number ends with the letter it is wide
deck (e.g., L-82374-27A). Body fit through-studs (wide deck) are a newer
design. They support the crankcase halves with an interference fit at the
crankcase parting surfaces and are tensioned at both ends with a 1/2-20 nut.
This increases the rigidity of the crankcase and prevents movement and
fretting. To make are long story shorter, buy a wide deck
Peter K SR003 .
----- Original Message -----
From: "Wayne G. O'Shea" <
oifa@irishfield.on.ca>
To: <
murphy-rebel@dcsol.com>
Sent: Friday, November 01, 2002 11:13 AM
Subject: Re: Lyc 540 terminology
WEIGHT!!
Seriously the main difference is that the cylinder bases of a wide deck
are
about 3/8" thick and the narrow deck's are 1/4" thick. The narrow decks
then
use a plate across the upper and lower 4 bolt sets of each cylinder to add
some strength. Wide decks generally have hex nuts retaining the cylinders
and narrows have internal wrenching nuts. Wide deck is <supposable> better
when it comes to chances of cylinder base cracking, but I don't think
there
is statistical evidence to prove that they are any better than narrow
decks,
BUT then again the "overbuild" makes it reassuring to own one!. The case
of
a wide deck is slightly more robust (read the engines are heavier!) and in
the case of an O-320 (and probably the 540) require a different alternator
mounting bracket than the narrow deck. The narrow deck uses a "case" mount
which picks up the forward lower bolts of the case halves and the wide
deck
uses a "boss" mount bracket that picks up at least two of the 4 available
threaded holes on a raised pad on the right half of the case.
Wide decks have an A after the last two digits of the serial #.
Example is the first O-320-A2B I have that is just coming out of ATC. It's
a
wide deck and it's serial # is L-30216-27A.
I also have another O-320-A2B that is a narrow deck and it just has a -27
at
the end of the serial # with no "A".
Cheers,
Wayne G. O'Shea
www.irishfield.on.ca
----- Original Message -----
From: "Jason Beall" <
super_rebel131@yahoo.com>
To: <
murphy-rebel@dcsol.com>
Sent: Friday, November 01, 2002 1:39 PM
Subject: Lyc 540 terminology
Hi all,
What's the difference between a wide deck and narrow
deck Lycoming 540?
Thanks,
-Jason
=====
________________________________________________
Jason Beall
Super Rebel No. 131
Aberdeen, Scotland, UK
super_rebel131@yahoo.com
__________________________________________________
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