So you need an engine for your 80 inch cub or a model with an exposed motor .
This four cylinder opposed dummy motor might be what you are looking for.
At 1.6 ounces assembled I wouldn't think that is would change your CG enough to notice.
If all you want is the cylinders to attach to the outside of the cowl; that is available on the site as individuals as well.
aprox 1/5 scale
4 1/4 inch front to back
6 3/4 inch from valve cover to cover.
There is room for an E-flite 15 outrunner inside