I have a corbin super ace, vintage...already built out, from the very early 80's. It was built with an OS 40 4-cycle. of that error. I still have that engine, but this plane is incredibly underpowered with this engine. This engine is installed to wooden rails, using blind nuts etc.

The current positions of the blind nuts are 8mm x 42mm

I have checked and an OS 56FS. It looks like it will fit the cowl, however the mounting bracket holes are

8mm x 44mm

Wonder if I can 'force' this to fit, or if i need to completely rework this mount configuration.

Trying to do this without 'carving up' the current configuration of the engine houseing and cowl etc.

Any other advice...

On wood motor mounts, what I do, is dribble in a little baking soda into the hole and then a drop or two of super glue, then some more baking soda followed with some more super glue. Then let it sit for a hour or two to ensure it is all cured real good. The baking soda chemically reacts with the super glue and forms a hard plastic like substance. Then you can redrill the holes as needed. You can even drill and tap the plastic like stuff that is formed too. I have used this to fix numerous engine mounts and holes over the years.
Baking soda and super glue makes for a good gap filler too. But it is harder than balsa wood though, so you have to be extra careful sanding it.

Another approach I have used is to pop out the blind nuts and then drill out the current mounting holes to the next convenient birch dowel size. then Using CA or epoxy, fasten the dowels to the drilled holes. Flush the dowels to the top mounting surface and then drill for the new mounting configuration. If you can't get to the underside of the rails to secure blind nuts to the new holes, get some "Nutserts from TruValue and insert them into holes sized appropriately. Nutserts screw into an oversize hole in wood to give you new metal screw threads. Kinda like Helicoils, but for wood and no need to pre-tap the hole for the Nutsert. Works for me.

Sincerely,. Richard

I do a little differently, I remove the blind nuts, put masking tape under the wood beam and fill the holes with 2 or 3 hour epoxy, refilling as it soaks out into the wood. It will soak up quite a bit, then next day just re-drill as if there were never any previous holes. If you overfill you'll have a hump that is difficult to remove. I do the same with firewalls where I change my mind or change engine mounts.

Richard, here's one where I used your method to replace a Saito 1.00 with a Saito .80.

all good ideas.... I need to 'get into this model' a bit, and see how i can remove some wood below the rails. The rails are mounted and under them is a large block of balsa that makes up the engine compartment and bottom part of the cowl etc.

So, i think first i need to excavate some balsa out below the rails so i can get o the blind nuts to remove them...then i think i can figure the rest out....with the methods suggested above.....

Thanks,
Chris

okay, looked at this tonight, going to be easier than i thought. Now to decide on the replacemnet engine.

have been thinking about several options since now i can resolve the mounting issue.

A saito, 56? or 62?

this was a .40 size glow 2 cycle kit....

VK Corbin Super Ace

Might as well go with the .62 its as much a sweetheart as the .50 and .56.