I took a few month break building my plane, as I was at the point I needed to glue the firewall in, but I needed holes drilled for the engine mount. I had no engine, so I couldn't continue. Anyways, day after Christmas, I got an engine.

How precise do the motor mount holes have to be. I mean if there a bit slanted or off center am I screwed? I glued the engine to the mounts, so the screw holes were completely on the mount, but just enough room, so I can angle the engine as the manual told me to do, then estimated center and marked the hole. The distance between the tops and bottom holes were alittle different, so I averaged them, and use that measurement as the distance the holds for the motor mount needed to be from each other. Is this accurate enough technique? I drilled the holes screwed the mounts on and test fitted the engine. It seems straight.

Thanks

Hi,
You do want the motor mount and the engine lugs to match up flats to flats. This prevents built in stress to cause a later break. If you have to redrill you can fill the old hole(s) with saw dust and epoxy. This way if the old and new holes are close it won't hurt a thing.

Shortymet55, you're probably ok as long as you can really secure engine. I do agree with OzMo that you want the engine mounts lugs "flat to flat". Avoid built in stress here like the plague. I prefer to have my engine mount as close to the crankcase as possible. If I need left or downthrust I just shim behind the engine mount. A little extra time here is well spent. If you haven't glued the firewall in yet, you might just cut another out.