A-65 Continental 100 Octane Valves: HELP!

Ok gurus,

Last Fall, I developed trouble in one cylinder (leakage past the exhaust
valve as evidenced by hissing sound coming out exhaust stack when
pulling the engine through).

It only appears to be one cylinder, but I thought now would be a good
time to pull all four and convert to 100 Octane valves. Since the
engine is on an Experimental, I can use parts from about anywhere (PMA
not required). I plan to buy the valves from Fresno Airparts.

Question: My A-65 Maint and Overhaul Manual lists 2 different part
numbers for exhaust valves. 22211 and 21479. It says the 22211 is for
the A50 and A65 and the 21479 is for the A75 and A80. According to the
Fresno Airparts ad in Trade A Plane, the 22211 is an 80 Octane valve (it
doesn't say that, but it doesn't mention it's for 100, so I ASSUME it's
for 80). The 21479 is listed as Stellite and for 100 Octance. My
question is: Is the 21479 for 100 Octane the same physical dimensions
as the 22211 specified for the A65 in the manual and will it work in my
A-65? They also list another 100 Octane valve (654066) for $70 more
than the Stellite valve. Is that one sodium filled or something? I
just want a basic 100 Octane valve in the old bug smasher...so will the
21479 fill the bill?

--
Scott
http://corbenflyer.tripod.com
Building RV-4
Gotta Fly or Gonna Die

Scott wrote:



Question:
The 21479 is listed as Stellite and for 100 Octance. My
question is: Is the 21479 for 100 Octane the same physical dimensions
as the 22211 specified for the A65 in the manual and will it work in my
A-65?

I think the two parts numbers are directly compatibles on any cylinder head.
read http://home.tele2.fr/philvsr/Cont_M64_6.pdf


During your work on the engine, check the rod hole diameter
http://home.tele2.fr/philvsr/ConRodBlueprintSmall.jpg

You may have a A75 after your work...

By
--
Philippe Vessaire Ò¿Ó¬

IIRC, the A75 had a slightly different carb venturi diameter and a
larger main jet in addition to the larger piston pin.

Dan

You are confusing the C-75 to C-85 which indeed used a larger venturi and
Main jet. The A-65 to A-75 change was basically just a change in the red
line. No Carb changes. The Large end of the connecting rod had to be
drilled for a squirt hole and this was done on the later A-65 for longevity.
The RPM was boosted from 2300 to 2600 by using a flatter pitched prop. The
A-series Continental manual also recommends a slight timing change for the
upper plug to 29° and the lower to 32° The Carb venturi is the same 1.25
for both the A-65 and A-75


--
Cy Galley - Aeronca Aviators Club
Newsletter Editor & EAA TC
www.aeronca.org
Actively supporting Aeroncas every day


wrote in message
oups.com...
IIRC, the A75 had a slightly different carb venturi diameter and a
larger main jet in addition to the larger piston pin.

Dan

wrote in message
oups.com...
IIRC, the A75 had a slightly different carb venturi diameter and a
larger main jet in addition to the larger piston pin.

Dan


The secret to getting 75 or 80 horses out of the A-65 is not in changes to
the carb but basically revving the engine higher. The A-65 gets 65 horses
at 2300 rpm, which is red-line. The A-75 gets 75 horses at 2600 rpm and
the A-80, 80 horses at 2700 rpm.

The NAS3A1 Stromberg carb uses a #49 main jet for all three engines and a
1.25" venturi. Larger jets and venturis are for the C-series engines.

I just rebuilt an A75 and did nothing to alter the carburetor but rebuild
the needle valve, although some people do rejet for experimental use. But
if you alter the carb it's not legal for a certified A-65, A-75, or A-80.

A few other differences: timing is staggered on the higher HP A-series
engines, and the cap end of each rod is drilled .063" to make an oil squirt
hole to spray oil on the opposing cylinder walls and pistons. The higher
horse engines have smaller diameter piston pins, but you have to make sure
you use the correct wall thickness because there is an AD against the
original pins. The exhaust valves have stellite faces on the higher horse
engines because of higher speeds and temperatures. And, btw, you can buy
that exhaust valve described by the initiator of this thread from Lycon for
around $100, and it is not sodium-filled. None of them are.

Pistons for the A-65, A-75, and A-80 have some variations. The A-75
pistons are same as A-65's except for a cooling relief cast inside the
hollow piston. They are 3-ringed and compression ratio is 6.3 to 1. A-80
pistons are 5-ringed and 7.5 atmospheres compression.

To the guy who started the thread, all valve dimensions are the same for
intake valves. And all dimensions for exhaust valves are the same.

I use the cheap valves because they are a better value and are quite durable
for the A-65. But I don't burn 100LL except as a lubricant for the seats.
Anyone who uses 100LL in any of the A-series engines (other that 1 part in
10 ratio, avgas to mogas) is asking for trouble, like sticking valves,
fouled plugs, crud, and accelerated wear. The compression ratio of these
engines is just too low for avgas, unless you can get 80 octane avgas.

If an exhaust valve starts to leak when the engine is low-time, I just
remove it, clean it, lap it back in with some fine lapping compound and
check for concentricity and guide clearance. It it's not burnt it will
work. Sometimes just exchanging the rocker arm or making sure dry
lifter-to-pushrod clearance is within limits cures the problem.

These are wonderful little engines and most problems with them are not
simple but not all that complicated either.

And, btw, if you go to 75 or 80 HP you have to re-prop. Check your tcds.

You can verify most of the above information by checking the official engine
overhaul manual. Buy a complete reproduction of the original manual, not
that shabby thing sold by Jim Irwin. It's like him--- more than a few
pages short.

Wicks has a manual they'll sell you.

Oh, and if you need a carburetor overhaul kit, don't buy that from Irwin
either unless you want to get shorted on crucial parts like those washers
used to set the float level. Fresno Airparts in Fresno, CA sells Stromberg
parts. So does Wicks.

excellent advice. I've printed it and stuck it into my engine log,
since I can't trust my memory anymore. I've been having some trouble
with the valves in my A-65, burning 100LL.

Dan