Filler/primer in the engine bay??

[dwranda]

I am working on the fiberglass plenum and inlets. I am trying to get them smooth and was wondering if using the filler primer is OK in that area. It says on the can not to be used in areas of over 200 degrees. I only want to use it on the inlets and not the plenum lid. I was going to use it to get them nice and smooth then cover with epoxy primer and paint. Opinions?

[Carl Froehlich]

Recommend mico followed by a bunch of sanding.

[dwranda]

I mixed up some micro balloons in epoxy and slathered it all over the outside of one inlet so far. The sanding is really taking the wind out of my sails. I know I will never build a composite airplane!! I am then experimenting with some drywall compound on the bottom of the inlet over the epoxy compound. That came out nice and smooth and filled in more imperfections. Filler primer is used by almost everyone on the canopy skirt so thought it would be beneficial on the inlets if I'm not worried about the temps. Wasn't sure if the epoxy paint would protect and seal the primer enough from the temp. Am I worrying too much about this?

[tgmillso]

I used West 410 filler mixed with their regular epoxy for most applications, but West 407 with the same epoxy for the cowling because of its higher rated temperature. I then sprayed it with a high build primer and cut it back to fill in the weave, then top coated with a white two pack polyurethane. The finish inside the engine doesn't have to be impeccable, the main thing is that it is relatively smooth and easy to clean. Anywhere near the exhausts I put Van's lightweight self adhesive aluminum film (ok, so 3/4 of my lower cowl is covered because these cowls are pretty tight). Don't forget to seal the sides of the inlet ramps to stop air escaping in a path that's not through the cylinder fins.
Good luck.
Tom.
RV-7