O-290 conversion to O-320
- Thread starter PA18project
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toobuilder
Registered User
Check Six said:
No worries about stud wall thickness, clearance issues, stroke, etc.? COOL!
Tom
I'm not going to say "no worries" because I have not yet built one, but I do know the 290 and 320 share the same stroke (3.875) and cylinder bolt pattern. I'm planning the same mod to a 435 (which is a 290 with two added cylinders). If you look at a 320 case, the stud is much closer to the edge than the beefy 290 case. Did Lycoming completely redesign the case to accommodate this change, or did they simply remove material from an overbuilt early case? Logic tells me that they were thinking ahead, and designed enough meat in the 290 to go oversize. I'd certainly do some investigating If I were you, however.
Steve Pierce
BENEFACTOR
Graham, TX
I have to talk to Ken today on about an engine. I will ask him.
Steve Pierce
BENEFACTOR
Graham, TX
Talked to him for over an hour about a couple of other things and forgot about this. He is supposed to call me back so I will see what he says.
Steve Pierce
BENEFACTOR
Graham, TX
Ken didn't know for sure but said if the bolt pattern was the same it should work. They do it all the time to make a 580 out of a 540. Might be worth looking into for an STC with no new O-290 cylinders out there.
toobuilder
Registered User
Steve Pierce said:
Did he mean a 480 out of a 435? A 540 shares the same bore and stroke with the 360. What bigger jugs are available to increase the size of the 540... the 390, perhaps? That makes a 585.
Steve Pierce
BENEFACTOR
Graham, TX
Lycoming is building a 580 by putting a bigger bore on the 540. Not sure what the equivalent 360 is. Ken machines the 540 and 360 case to except the bigger bore cylinders.
Clayton Harper
MEMBER
Seabrook, TX
Back to the O-290s, I think I heard that the "narrow deck" O-320s started out with an O-290 casting, with the hole for the cylinders bored out to accept the O-320 cylinders. That's why the NDs have internal wrenching nuts for cylinder bases. I have a 320 and a 290 in my shop, I've been meaning to measure but have not yet.
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scubber
SPONSOR
Delevan,NY
I know that an 0320 crank fits in the 0290D2. Mine had one when it was opened up for major. Overhauler talked to Lycoming to see about paperwork to make legal as it wasn't addressed in the log, other than being replaced, part no. such & such. Lycoming rep. said it was done often a long time ago. Said they are basically the same except the 0320 has a heavier flange. He said in today's "environment", they no longer will give "paper" or memo to install legal. Larry C.
Back in the early 80's I built a engine using a Lyc-290 case, 320 crank, 290-G, cam with solid lifters, 290-D2 high compression pistons and jugs, ported and polished intakes, Four into one exhaust system with no muffler. Would turn a Sen- 74"X56" prop, ( 150 hp, 320 Super Cub prop) at 2900 rpm WOT. Put a lot of hrs on it. Very good engine. Everyone ask if it was a Lyc -360. Dan
how to convert 0-290d or d2 to an 0-320
I looked at the sump for a 290 and a 320 and it appears the mount and intake inner diameter for the carburetor are larger for the 0320 and therefore changing sump would be required. A MA4-spa carb would be required. Anyone have tips on jetting needed or would any ma4-spa work?
For the case: yes a 0320 is a punched out 0290-d2 as far as I have heard, makes sense. Any machine shop should be able to do it for your air boat. Would you have to machine out a 290d case to accept hydraulic tappets? I bet the d case would only work for the conversion if you stuck with manual tappets and the lower lift D cam.
Camshaft: the cam for the d2 has the higher lift than a d cam. Are 0320 and d2 cams the same part number?
There are two types of cams. Integral and seperated. Does anyone have any pics of the different tach drives required for each?
Crank: the 290 crank would have a thinner flange than a 320 crank. This is the only area that makes me uncomfortable. Possibly welding on the half moon doublers from aircraft spruce would suffice? A 290 crank is I believe 10lb lighter than a 320? I wouldnt go over the 150hp pistons without a 320 crank. (GOT IT, NO WELDING ON CRANK, BAD IDEA, stress fractures) moons were bolt on for the gpu 290.
Prop: I would go catto. It's lighter so stress should be less on the crank from each ignition stroke right?
Perhaps we can compile some real information. All I have found on this conversion so far is speculation. Lets get some part numbers going etc.. if people are really interested.
I am curius if the new d crank I have will work for the conversion. What's the difference between d and d2 cranks?
Ans: from answers below, D and D2 cranks are interchangeable. As is the 320 crank.
I also read something about the 320 cam being put in a 290 and since it was longer it caused oil to sling out the breather? Anyone know anything about that?
I looked at the sump for a 290 and a 320 and it appears the mount and intake inner diameter for the carburetor are larger for the 0320 and therefore changing sump would be required. A MA4-spa carb would be required. Anyone have tips on jetting needed or would any ma4-spa work?
For the case: yes a 0320 is a punched out 0290-d2 as far as I have heard, makes sense. Any machine shop should be able to do it for your air boat. Would you have to machine out a 290d case to accept hydraulic tappets? I bet the d case would only work for the conversion if you stuck with manual tappets and the lower lift D cam.
Camshaft: the cam for the d2 has the higher lift than a d cam. Are 0320 and d2 cams the same part number?
There are two types of cams. Integral and seperated. Does anyone have any pics of the different tach drives required for each?
Crank: the 290 crank would have a thinner flange than a 320 crank. This is the only area that makes me uncomfortable. Possibly welding on the half moon doublers from aircraft spruce would suffice? A 290 crank is I believe 10lb lighter than a 320? I wouldnt go over the 150hp pistons without a 320 crank. (GOT IT, NO WELDING ON CRANK, BAD IDEA, stress fractures) moons were bolt on for the gpu 290.
Prop: I would go catto. It's lighter so stress should be less on the crank from each ignition stroke right?
Perhaps we can compile some real information. All I have found on this conversion so far is speculation. Lets get some part numbers going etc.. if people are really interested.
I am curius if the new d crank I have will work for the conversion. What's the difference between d and d2 cranks?
Ans: from answers below, D and D2 cranks are interchangeable. As is the 320 crank.
I also read something about the 320 cam being put in a 290 and since it was longer it caused oil to sling out the breather? Anyone know anything about that?
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The 320 crank will bolt in the 290 case, the 320 crank just has a thicker prop flange. No difference between the290- D and the D2 crank.
As I posted earlier, I used a 290-G cam and solid lifers because I had then on hand.
Also used 290-D2 pistons and 320 carb.
If you don't like the thinner flange on the 290-D crank, there used to be a flange reinforcement kit for the thin flange cranks on the Lyc-290-G conversions that you could use to the 290-D crank.
So you basically built a 290 with a bigger ma4 carb and sump to add more air flow through the motor and get more rpm. Sounds like a very simple way to get a few more ponies. Did you have to run Avgas? Get any detonation? Did u use 7.5:1 pistons or something higher? I have the 6:1 low compression d pistons currently and would prefer to keep running 3 dollar gas rather than five fifty 100 ll if possible. That's to me why the low compression 150hp 320 pistons were attractive. What do u think
If you would look at my earlier post, I used the high compression D-2 pistons, 320 crank for the thicker flange, 290-G cam and solid lifter because I had them, 320 carb and ported and polished and matched all the intakes, 4 into one exhaust system with no muffler. Used 100 av fuel about 3/4 of the time but had no problem with High grade of auto fuel. I believe it was putting out about 165-170 hp. I don't know how different the 290-G cam is compared to the D- or D-2 cam, but at idle it had a definite lope that would shake the wingtips up and down about 3-4". Very strong engine. Flew it 5 years traveling all over the U.S. 1700 FPM ROC at GW,( 2100 FMP with just me) and cruised at 155 mph.
Looking at 0-320 on wickipedia it says they mostly all used a ma4-spa-32 carb for both 150hp and 160hp.
7:1 takes anything
8.5:1 makes 160hp takes 91/96 Avgas
9:1 takes 100ll only
I bet your idle wasnt due to the cam but from a larger carb. Larger bore carbs flow better up top but sacrafice idle smoothness
Heard a guy replaced a MA4-5 carb temporarily with a ma5 off a o-540 and noticed same thing.
7:1 takes anything
8.5:1 makes 160hp takes 91/96 Avgas
9:1 takes 100ll only
I bet your idle wasnt due to the cam but from a larger carb. Larger bore carbs flow better up top but sacrafice idle smoothness
Heard a guy replaced a MA4-5 carb temporarily with a ma5 off a o-540 and noticed same thing.
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That was back in the early 80's and I don't remember what the C/R was. But I loved that engine. If I have it today it would go in my Bearhawk project. I live on a runway and one of my neighbors was a IA and he always thought it was a Lyc-360 by the way the aircraft performed until I told him what it was. Dan
skywagon8a
MEMBER
SE Mass MA6
I have been reading this thread only out of curiosity with no intention of performing any of these mods myself. However, your above statement gives me pause. Welding on a crankshaft flange?? This seems a bit risky without further explanation. I assume that these half moons are placed behind the flange and are welded around the outer circumference only? And, that the crank was checked for magnetism and balance afterwards? How does this extra flange thickness transfer the stresses into the crankshaft? Through the old thin flange? I am assuming (hoping) that you did not weld the inner portion of the half moons to the crank where the stresses from the propeller loads are the highest and where the flange could crack from the welding? Just asking. And asking that you please not invite me for a ride.
As an aside, I have seen crank flanges which were cracked between the lightening holes in all but one section. The propeller was close to departing the airplane. This was on a TriPacer. Just food for thought.
100 % correct DO NOT weld on the crank. The prop flange reinforcements that was sold for the Lyc-290-G conversions back in the 60's/70's was two half moons that fitted together behind the prop flange and bolted to the crank flange with the prop bolts. I had one at one time back at that time and think I gave it to someone that needed it. The 290-G ground power unit crank had a prop flange thinner that the aircraft 290-D. I think it was the same as the Lyc-235.
Dan
Randy
FOUNDER
S.Dakota
Dan D, wrote: The prop flange reinforcements that was sold for the Lyc-290-G conversions back in the 60's/70's was two half moons that fitted together behind the prop flange and bolted to the crank flange with the prop bolts. I had one at one time back at that time and think I gave it to someone that needed it. The 290-G ground power unit crank had a prop flange thinner that the aircraft 290-D. I think it was the same as the Lyc-235.
Dan. Dan, I think the 0-290 "G" crank was indeed a crank from a lyc -235. I have a 0-290 "G" without the flange reinforcements...was wondering where I might find a set of them...
Dan. Dan, I think the 0-290 "G" crank was indeed a crank from a lyc -235. I have a 0-290 "G" without the flange reinforcements...was wondering where I might find a set of them...
I don't know where you could find a set. The reinforcements were formed to the radius of the rear of the flange. Also it took longer prop drive bushing because of the thickness of the reinforcements. Aircraft Spruce used to list them in their old catalog years ago. If you called them, they might be able to give you the name of their supplier. I'll look through my boxes of parts and see if I might by chance still have them, but I haven't seem them for a long time. Dan
Is the cracking through the lightening holes the reason they say max power only for 5 minutes? What is the origin or reason of this statement? Perhaps I should make sure that's on my annual inspection list.
How much material are you taking off the intake port walls? Any particular areas? I assume you could use a dremel for grinding and polishing?
How much material are you taking off the intake port walls? Any particular areas? I assume you could use a dremel for grinding and polishing?
skywagon8a
MEMBER
SE Mass MA6
This was on a 0-320 either a 150 or 160 hp, I can't remember which. The cracks were only found when the prop and ring gear were removed for some other reason. They appeared as very fine rust lines. And no, there was no time limit for full power.
Did you have to do any jetting when swapping to the 320 carb and sump? Smoothe acceleration, or any coughing?
No re-jetting and it ran great. Smooth and powerful.
Removed just enough material in the intakes for a good polishing, and matched the ports so the insides were inline.
