I,m ready to install a new gas engine & not real sure how to make it come thru the cowl opening perfectly. I dont want to have all kinds of drill holes that dont align. Thanks guys....

Make a block of wood the pattern of the rear engine mount plate.

Extend a dowel from this plate that represents the center line of the engine

Locate the dowel in the center of the cowl opening

Where the wood block sets on the firewall is where you want to mount the engine

Don't forget to allow for engine thrust angles

here's one thing i do...using the main gear, i hang the fuse on a gate between my garage and patio...i secure the fuse with string to keep it from falling off the gate, and use a step stool for a work platform...the firewall is then horizontal, and it's much easier to align the engine, standoffs, and cowl...you can position the engine with standoffs to the exact location where your hub/cowl is centered, draw circles around the standoffs on the firewall, make an 'x' in the four circles, and drill...or use a template that comes with your engine...ken

I like W8ye's method better. The dowel tool is a keeper for the next project.

For cylinder cutouts in the cowl side, I make the cutout in a cardboard template. Fit the engine, fit the template over the engine, and tape it to the fuselage.
Remove engine, fit cowl, and trace the template still attached to the fuselage. That will be exact cowl cutout location.

W8ye, that sounds most logical to me!!! Why the heck couldnt I figure that out......anyway, thank you for that tip.

It worked out great....