Cowl Inlet Ramps

I've been working on my baffling (Oh joy!) and need to fiberglass in the upper cowl ramps so I can begin trimming. The ramps seem to only fit well in one spot but there is a decent gap along the side. Does the rubber make up this gap or do I need to favor the outside more?

I searched and found quite a few ramp pictures of green cowls, but the ramps seem wider or the inlets are narrower.





I plan to trim simular to this. (Thanks Rick)

You are thinking right

This is a area that is definitely not put tab "A" into slot "B". I posted some work on this years ago. The rubber has to be thought about a lot and it has to be installed in such a way that it seals everywhere - even in the areas forward of the baffle metal in the front of the cowl (inboard and outboard) and the sides of the "ramps" you are thinking about. For the ramps to seal you have to close of the sides. I used foam and epoxy. I think most people do nothing in this area and there are a lot of leaks remaining - perhaps even some cooling problems.

Bob Axsom

Thank's Bob.

Has anyone with the newer pepto pink cowl found it necessary to widen the inlet ramps?

Lots of ways to do it

There are almost as many solutions to this as there are RV's.

One big choice is whether to make the baffles seal onto the ramps themselvs, or bypass the sides of the ramps and seal on the cowl surface. I think a lot of people do one of each - the outboard baffle seals onto the ramp, but the inboard baffle (around the front of the engine) seals to the cowl top. Thus the channel through the ramp must be closed off.

What I did was maybe unusual, but seems to work fantastically well. I extended the ramps outboard to intersect with the cowl side. This gave me all the width I could want to make sure the outboard baffles had a good surface to seal on. It seemed to me that the ramps were just a bit narrow and it might be possible for the rubber seal material to miss the ramp and fall outboard of the ramp edge, just as you are thinking. So widening the ramp all the way to the side of the cowl prevented that.

Then, I closed off the inboard end of the cavity under the ramp with an angled "rib" that blends smoothly onto the cowl surface. My rubber baffle material on the front baffle makes a transition from sealing against the ramp, to this angled side rib, to the upper cowl surface. This was pretty complicated to figure out at first, but seems to make a complete seal around the front of the engine.

My cylinder temps are 260F - 290F at cruise (24 squared), and on a 90F day, a climb to 8000 ft gave max cylinder temp of 375. Thats the hotest I've ever gotten.

Its an IO-360-A1A (angle valve 200 hp).