O-290D2 into a O-320A2B narrow deck case

I hope I'm posting this in the right place.
I have seen some discussion about cutting the O-290d2 case cylinder holes to accept O-320 narrow deck cylinders.
I have over some time now been gathering rebuilt stuff for my O-290D2, case, crank, lifters, cam, etc. I am just about to buy the bearings. However I just accidentally bought an O-320 A2B narrow deck which isn't much good, so I got thinking I wonder if the rebuilt crank, cam, lifters from my O-290 can be used in the O-320 case and which rods can be used with the O-320 cylinders and pistons if this is possible? It appears that the crank from the O-290D2 is very close to the O-320 crank except for the bent flange.
Robert

Maybe compare part numbers from parts manuals?
https://www.lycoming.com/sites/default/files/O-290-D Parts Catalog PC-102-1_0.pdf
https://www.lycoming.com/sites/default/files/O-320-A2B,-A3 Parts Catalog PC-203-1.pdf

Thank you Gordon for the links, I'll give it a good look. Seeing that I have had my O-290 case redone I may just send it in to have it modified.
Regards
Robert

Hi Robert,
I have 2 O290D2's for my 2+2 project; one used and one overhauled and pickled. The O290D2 case can be worked to take the O320 jugs but can't be used as a certified engine with the mod; only used for an experimental. What is your O290D2 intended for, certified or exp? I have an extra set of O290D2 rods if you need a set.
Marty

Hi Marty,
I'll be using in an uncertified aircraft. Thanks for the offer of the rods, but I have two O-290D2s, so I have extra parts with the exception of a crank in one. I have also a 320 narrow deck with a bent crank flange. The front main bearing is one large one instead of two like the 290 has, so I'm not sure about the compatibility of the 290 crank in the O-320 case. The crank looks the same but there is a different hole setup in the front part of the shaft.
Robert

Robert,
One of the reasons the 0290's blow so. much oil from the breather tube is
the case design compared to the 0320's. The forward mounted exit position on the 0290 breather tube was a very poor location, because of its alignment with the end cam lobe .
The airboat boys in Florida have a mod to add a rear exit casting over the
vacuum pump pad. That combined with some balance preasure holes they bore, is know to reduce 0290s oil
blow back in half or more.
Increasing the cly flange holes to accept 0320 clyinders is "THE BEST" mod you could ever do to an 0290 simply because there are ZERO "steel barrel" low time clyinders availability.
So your always going to face trying to break in "Rechromed clyinders" that likely have many thousands of hours on them right outta the box........
There would be a huge advantage using the 0320 case with its rear exiting breather position and its differential porting already there.
The 0290 is a great old engine but in todays world of " no clyinder support" you will be looking at approximately
Double the cost per hole for stud Assembly that has likely been overhauled many times, the piston situation is even worse. NEW 0290 D2 pistons will fetch ridiculous prices.
So there are a bunch of great reasons
to put the 0290 stuff in the 320 case if you can. Top overhauling the 0290 has become a total nitemare clyinder wise. There has been ALOT of failures
with clyinders in recent years simply because they are so old with so many TT hours on them nearly ALL of them have had the aluminum tops rewelded for cracks numerous times........
Divco used to rework 0290 clys with 0320 valves for us with "white tags" part of that conversion includes replacement of the allison seats for the new valve stem diameter. The 0290 seats wont have enough left to them to simply regrind them , to match the 1/2" tulip.
If you quiz El Reno they will inform you. They have hundreds of names on a list , of folks wanting to purchase new 0290 D2 pistons......... But they have NONE to sell.
Good luck with witch ever way you go,
I know of two recent top overalls on 290s that the clyinders came outta a shop in Texas and both have had clyinder failures shortly after installing
the reworked ones. Its a slippery slope
that is now in the $ 8000 dollar range to try your luck at a top overall a 290 just for the parts......... I wish you the very best of luck on your project.
E


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Marty57 said:

Hi Robert,
I have 2 O290D2's for my 2+2 project; one used and one overhauled and pickled. The O290D2 case can be worked to take the O320 jugs but can't be used as a certified engine with the mod; only used for an experimental. What is your O290D2 intended for, certified or exp? I have an extra set of O290D2 rods if you need a set.
Marty

Click to expand...

What cylinder the narrow deck or wide deck? And how much modifying do you have to do?


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TurboBeaver
Yes, thanks for the luck. We'll see how far I get with using the 320 case, if no go, I'll send the 290 case out have it modified.
Robert

Welcome. A guy in FL had a gig to overbore the clyinder base holes out to accept 0320 clys. " Outlaw Engines"
Used to be $100 a hole from memory.
Probably lots of shops giged up by now. Again good luck with the project.
E

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