Does anyone close off the opening's from the engine compartment to the airframe to help keep pressure and heat from entering?

Robert, I have only heard of one case where the pressure got high enough to blow covering off. Looking at your Pitts I would say you have enough " leaks " to keep from that happening. As far as heat goes I wouldn't worry too much about that either. The IMAC guys flying composite airplanes and canisters and just burying the canisters in the fuse without anything separating the radio gear from the exhaust system. I have had a couple wood and foam 40% airplanes with open motor boxes as well without issue. Those were Monokote covered and the covering you plan to use will stick to the airframe much better.

Speed don't those canister ones come with a closed box they go in. All the ones I have seen was. It does not matter I have closed it off. It was more of an idea for discussion.

I worry more about oil than about heat and pressure. I've never had a plane blow up or cook any electronics but I sure have had a few that fell apart from being oil soaked.

Dave

Although the OP dosent say my reply was for gasoline powered models. For glow of course you would want a sealed engine compartment.

The gasoline engines don't use as MUCH oil but there's still some. So it's still prudent to seal off any pushrod and fuel line feed through openings to keep out the oil contamination.

For any and all glow engine models that I've ever done it's just simply something that is done.

For sealing the fuel line feed through points I always drill the birch ply and smoothen out the holes with a nice rounded flare on each side. I size all this so the silicone fuel line passes through with a good amount of firmness. But open enough that I can push the stub of tubing through then pressure seal it to the firewall passage by inserting a stub of brass tubing to force the silicone out tight to the wood.

The stub of brass tube then becomes the attachement point for the line to the actual engine.

I'm guessing that the equivalent should work for a gasoline engine. Or just by the threaded feed through fittings.

If something like this is to be used it should have barbs on each end, just about every type of gasoline line I have used swells slightly after being exposed to gas. Even worse with ethanol blends.

Ok, well, the engine of choice for this particular airframe I am dealing with is a Valach 170, gas. All mine are now gas. Most planes be it kit, ARF or what ever end up with a pretty closed up firewall between the engine and airframe. But this one is not so because of the orientation of the carb, rear and offset low. The pics 1 & 2 are a front and rear view and that opening went all the way through, but I have closed it off as seen in pic 3.
So by the responses I did the right thing. Great!!

Yes, I figured it was a gasser. But as BMatthews said, there is still oil. I never expect my planes to live forever but sometimes I get pleasantly surprised. And finally finding out that a favorite old airplane has oil soak damage is disheartening. Anything that can be done during construction to extend the life of an airframe is time well spent for me.

Dave

I had pressurization issues in my Wedell Williams Racer. The abs plastic cockpit and canopy cracked and was getting blown up and out. I added venting in the fuse and cured the issue.

Pete

An update. The engine compartment is completely closed off to the fuse. And I have given the engine compartment three coats of primer and two coats of clear. So it is oil proof and leak proof. And the white makes a nice backdrop for the engine.