It's a good motor, though parts are getting scarce. Like all Lycomings, they don't like sitting for long periods, the cam can rust. It wouldn't be my pick for a new plane, but I wouldn't rule out a plane just because it had an O-290.
I have a G with a D crank. Some parts are hard to find, if they have to be 290, but if the engine is going through an overhaul it can be converted to a 320, assuming it’s a homebuilt, with machining to the case and 320 cylinders and pistons so it can live forever. Lycoming did the same and decided to drop the 290 instead of make two engines close to the same. A company called Gibson does a lot chroming 290 cylinders if you need to keep it a 290. Kind of what they are known for.
If it’s running now, fly it. Nothing wrong with one.
74 million Tri-Pacers flying around with O-290 engines on them. Perfectly good engine for what it is. As Dana and TFF said, nothing wrong with it if all you need is 125HP. Convereted to higher power easily enough.
Not as valuable or desirable as the O-320, but the 290 is usually less expensive on the used market. If you can buy the O-320 for $500-800 more then buy the 320. If the 290 is $X and the 320 is $1.5 or $1.8X, and your airframe is happy with the 290, then save the money.
What type of airframe is this going on? Long-EZ... Fly-Baby...Wag-Aero Cub...Cassutt????
Most of the O-290 stuff outside of the crankshaft and case is also O-435 parts, same p/n's. I think cylinders, rods, pistons, bearings, valves, lifters, some of the gears. So although the 435 is also a "forgotten" or obsolete engine, if you find parts for that you have also found parts for the 290.
Now the 435 and 290 are not known for fuel efficiency or the most modern design. They were definitely made obsolete by the 320 and 540.
Again, I'm pretty sure this boils down to cost. The 290 is perfectly safe and reliable, with millions of fleet hours, and no big "gotcha" problems other than obsolescence.
And as Pops said, they will make 135-140HP easily. My RV-3 had the 290-D2 in it and was perfectly reliable.
Questions that frequently are asked of Lycoming sales personnel, engineers, and technical representatives indicate that there is a myth regarding Lycoming piston engines. This myth seems to be prevalent among aircraft owners and aviation writers. In the minds of these individuals, each Lycoming engine series is essentially the same. For example, all 360 cubic inch displacement engines are inherently the same except for differences in fuel metering or turbocharging. The idea that these engines are the same is false. A few specific examples may help to put this myth to rest.
Lycoming builds 0-320 engines that produce 150 HP or160 HP. The 150 HP O-320-E series engines operate at a compression ratio of 7.0:1. The 0-320-D series has high compression pistons which raise the compression ratio to 8.5:1, and increase rated output to 160 HP. Those who believe that the pistons are the only difference in these engines will be disappointed when they plan to upgrade their 0-320-E to the higher horsepower by simply changing pistons. Many models in the 0-320-E series were designed for the purpose of keeping the cost down. Thousands of these low compression engines were built with plain steel cylinder barrels instead of the nitrided barrels used in the 0-320-D series engines. They also had two narrow bearings instead of one long front main bearing. The engines were certified at 150 HP and were not intended to withstand the additional stress of higher horsepower.
Because of the similarity in designation, it would be easy to believe that the 0-360-A1A and the IO-360-A1A are the same engine except that the first engine has a carburetor and the second a fuel injection system. Here are some features of each engine for comparison. The 0-360-A1A has a bottom mounted updraft carburetor, parallel valves, 8.5:1 compression ratio, and produces 180 HP. The IO-360-AIA features a horizontal front mounted fuel injector, angle valves, 8.7:1 compression ratio, and is rated at 200 HP. The IO-360-A1A also incorporates these design items which are not included in the 0-360: piston cooling nozzles, stronger crankshaft, tongue and groove connecting rods with stretch bolts, tuned intake system, and rotator type intake valves. There are actually few similarities except for the 360 cubic inch displacement.
There are individuals who have suggested that by putting 10:1 compression ratio pistons in an IO-360 engine, it couldbe the same as the HIO-360-D1A. These are some characteristics of the HIO-360-D1A helicopter engine that can be compared with the data on the 10-360 listed in the previous paragraph. To start, the HIO has conical rather than dynafocal mounts. The main bearing is a thick wall bearing instead of the thin wall, high crush bearing used in the I0-360. Other differences include: crankshaft designed for small crankpins, high speed camshaft, rear mounted RSA7AA1fuel injector, large intake valves, and torsional vibration damper magneto drives.
Finally both the Navajo engines and the new turbocharged Lycoming used in the Mooney TLS are equipped with differential and density controllers that automatically set the maximum allowable horsepower when the throttle is advanced fully for takeoff. Some who have not taken the time to compare these engines have jumped to the conclusion that the TIO-540-AF1A which powers the Mooney TLS is simply a derated Navajo engine. This conclusion could hardly be more inaccurate. The most obvious difference, even to the complete novice can be seen by looking at the rocker box covers. The TIO-540-AFIA is rated at 270 HP and has parallel valve down exhaust cylinders. The Navajo series has three engines at 310 HP, 325 HP, and 350 HP. All have cylinders designed with up exhaust and angle valves. Other differences respectively in the 270 HP AF1A and the Navajo series engines are: small main bearing instead of large main bearing, 8.0:1 compression ratio rather than 7.3:1, intercooled and non-intercooled, pressurized Slick magnetos versus Bendix/TCM magnetos, and an RSA5AD1 fuel injector in place of the RSA10AD1 injector. There are some other differences, but those comparisons listed should convince even the most skeptical that these engines are vastly different.
By making comparisons of various parts and accessories used in engine models which some individuals have considered to be much the same, it is possible to illustrate the differences. Although some Lycoming models are closely related, this cannot be assumed. A review of the engineering parts list for each engine model by a knowledgeable individual is the only sure way of establishing similarities and differences. For those who may have been taken in by the myth that all Lycoming engines of a particular displacement are very much the same, you are now armed with a better knowledge of this subject.
The hard stuff is the cylinders and rings. There have not been new Cylinders since the 60s. Valves can be updated to 320 so no problem there. Rings are available but sometimes you might have to wait or over pay. Look at the prices at Aircraft spruce for 290 and 320 rings. Aircraft Spruce is sitting on some old stock and is waiting. Cam would have to be a O-235 if you just had to have new and not reground. I do think they hold the same part number now. Crank can be updated to 320 one, rods too. Bearings the same.
I would like to do a G engine from scratch but it’s not economical. You would have to be very lucky on the conversion core. Same with an engine that needs everything, but if you can pick up a good candidate, do it.
You do have to know the difference between wide and narrow deck.
The original rare O-340 was a 290 with a 360 crank. There have been some hot rod crazy ones. Someone made a angle valve 340 from a G motor. Angle valve 435 helicopter cylinders with some kind of custom pushrod to adjust the valves with Bendix pressure carb. You see a lot of semi aerobatic 290s with small engine Bonanza pressure carbs that are modded. Popular in the 60s.
I built my hotrod Lyc 290 in 1980. At that time parts were cheap. I paid $300 for a good standard 320 crank. Started with the 290-G case. Loved that engine. Wife and I traveled behind that engine for 5 years and put somewhere between 750-800 hrs on it, if I remember right.
Thanks for all the information man there’s a lot to learn but yes I got to checking on parts and there are far and few between I never did find a good source for anything I could find a part here in there most places do not list the 290 so I’m gonna start looking for a 320 or something around that size I appreciate all the information you guys give