Lightest Lycoming?

[SHIPCHIEF]

What is the lightest Lycoming as used in an RV4,6,7,8?
Is it the narrow deck models?
Does the conical mount weigh less than the dynafocal ring?
Are some cylinders heavier than others (I mean parallel valve units).
Crankshafts, Hollow, solid, certain part#'s? (counterweighted would be heavier).
Looking for the lightest base engine, then add the lightest accessories.
Might consider O-360 over O-320 if it's close.

[RVbySDI]

Look at the ECI O or IO-340. My IO-340 weighed 250 lbs before any accessories.

[curtis]

The weights of the engines are listed on the Type Certificate Data Sheets. This data can help you decide based upon engine model, weight, and HP.

http://rgl.faa.gov/Regulatory_and_Gu...e?OpenFrameSet

[Rhino889]

Originally Posted by SHIPCHIEF

What is the lightest Lycoming as used in an RV4,6,7,8?
Is it the narrow deck models?
Does the conical mount weigh less than the dynafocal ring?
Are some cylinders heavier than others (I mean parallel valve units).
Crankshafts, Hollow, solid, certain part#'s? (counterweighted would be heavier).
Looking for the lightest base engine, then add the lightest accessories.
Might consider O-360 over O-320 if it's close.

ShipChief,

Is the rotary getting swapped out!?

I've followed your build with great interest.

Regards,

Scott

[SHIPCHIEF]

Well that was a slog, going thru the type certs...
But it did reveal a few gems.
The lightest O-360 weighs 10 lb more than the lightest O-320.
Without detail, other than suffix nos., I would assume that a number of these engines were without fuel pump, Vacuum pump and Governor, for a base model Cessna 172 or something.
Low compression models seem to be lighter.

[SHIPCHIEF]

Scott (Rhino);
The Rotary in the RV-8 is doing fine. I'm working on wiring & avionics, wrapping up the lighting & wingtips. I'm getting very good Static power, and the cooling system works very well on the ground.
My wife is a CFII and very competetive, but won't be flying the RV-8 due to the Rotary engine.
I've picked up a Thorp T-18 from a guy that can't fly anymore. It has an O-290G, converted to an O-290D2. Well sorta: It still sports a solid tappet cam, and the mounts aren't converted to conical. It has an O-320 crank, sump, & gearcase. It runs very well, has 267 Hrs AF & E, but it sat for 9 years.
So I've become interested in Lycomings after all.
Never one to do things the easy way, I have to wonder about the parts interchangability, and also the product evolution.
In this reguard, Lycomings seem to be amazing.
T-18s are very small & have very small wings. Keeping the weight out of them is even more important than on an RV.
So I'm looking down the road, it's obvious to me that I'll be a repeat offender, but likely only one Rotary. It's been fun, but also a lot of developement work.

[smokyray]

Scott,

The IO-233 is the lightest currently. The 0-320A ND is the lightest way to get 150/160HP. Lycoming weight specs the ND 0-320A at 12 lbs lighter than the 0-360 A1A. They are also very reasonably priced and provide mucho bang for the buck. They do require the straight (conical) engine mount. I have extensive experience with the model if you want to email me off line. smokyray@rocketmail.com

V/R
Smokey

PS: My original 89' RV4 had a Narrow Deck 0-320A with wood prop, no alternator, no paint, Lexus starter, motorcycle battery, solar panel, automotive gauges. 918 lbs. My current RVX also has a ND 0-320A (the other engine off the same Apache) with a Catto and minimum equipment/paint and interior. 940 lbs. Both airplanes perform very well.

[SHIPCHIEF]

Smokey;
I've noticed your posts in the past, seemed to present the 'less is more' approach that VAN's advocates.
I won't be buying a new IO-233, but I would be interested in putting together an O-320 connical ND.
I'll be happy to take you up on that offer.

[N941WR]

Scott,

When I changed from an O-290-D2 to the ECi O-360 I opted for the hollow crank (Who knows, I may add a CS prop someday.) and their tapered cylinders (1.5 lbs lighter than standard).

Other things I did to keep the weight down was to use P-mags (~1.5 lbs lighter than a mag, net 3 lbs savings), the smallest Sky-Tec Starter, the B&C 60 amp alternator, and Catto prop.

With all that, my new engine mount is 2" shorter than the one I had with the O-290-D2. My CG worked out perfect.

[mahlon_r]

Be careful using the weights that are listed in the type certificate data sheets if you are looking for complete accuracy. They are the actual weights of the engine as certified when it was certified. The accessory configuration of the engine when it was certified can have a big effect on the weight listed. Some engines were certified with alternators or generators and others of the same model were not. Also the type of starter, mags, etc. used can have an effect. Also as crankcases were changed over the years the weights of the engines change by a bit but the TCDS weight doesn't change. It is a good ball park figure to use but not gospel.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."