Ditto on Bipe Flyers comments......I have never found any brand epoxy that holds up when exposed to high nitro fuel, even when a coat of fuel proof paint is applied, it turns brown and softens. Just fixed up such a mess after removing an engine in a cowled in application. The paint held up, but the epoxy underneath didn't.

Should have stuck to the only menthod I have found that works, CA glue. If you want to color the engine bay, CA glue, a coat of acrlic artist paint and then more CA. I have models with hundreds of flights that have CA sealed firewalls and not a problem.