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Cowling inlet ducts affect on cooling?

smithflys23

Well Known Member
The upper cowl of my -8 does not have them installed, and I am experiencing high CHT's on #2 in the climb. I am wondering what kind of temp decrease I might experience if I go back and install them. I have also read that one end needs to be closed off.
P/N: Cowl, 8 Inlet left/right.

Any help is appreciated!
 
Inlet ducts

What is special about the "cowl, 8, inlet duct"? Is it a complex shape or are there detailed instructions with the parts? They weren't included with our finishing kit and there is very little information about them in the documentation, nor can I find them on Van website.

Is there any reason I can't fabricate these myself?
 
You can make them

You can build or buy them - search Van's store for "inlet right" and "inlet left".

They came in my finish kit, but nothing special if you wanted to build them - each side is a fiberglass piece that creates a smooth transition from the inlet to the surface of the upper cowl. They are about 11" front to back and the rear is about 11" wide and attaches using flox just inside the inlet of the upper cowl on one end and to the upper cowl itself on the other.

Bob
 
You can build or buy them - search Van's store for "inlet right" and "inlet left".
Bob

Having just ordered these, they can be a little tricky to find on the Vans store.
The actual part name from the plans is “cowl 8 inlet left” and right respectively. They are a little pricey At $43 per. I’m hoping that installing them will help my cooling issue.
 
I don't have them either and also suffer from high CHT's. Going to be installing them in the next week or so. Will report back.
 
I don't have them either and also suffer from high CHT's. Going to be installing them in the next week or so. Will report back.

I’m interested to read your results. Oddly enough, my #2 is my problem.

Also, I’d be curious to hear about your instal. The plans call for drilling holes while bonding them to the upper cowl. I’m wondering if that’s necessary on a cowl that’s already fit to the fuselage.
 
I am not planning on cleco them, I think I can get around that easily enough.

I’m interested to read your results. Oddly enough, my #2 is my problem.

Also, I’d be curious to hear about your instal. The plans call for drilling holes while bonding them to the upper cowl. I’m wondering if that’s necessary on a cowl that’s already fit to the fuselage.
 
Also, I’d be curious to hear about your instal. The plans call for drilling holes while bonding them to the upper cowl. I’m wondering if that’s necessary on a cowl that’s already fit to the fuselage.

Not at all. Just rest the cowl top upside down, epoxy them in place using a couple of pieces of duct tape to lock in the location, and put some weight on them so you get a good squeeze on the glue joint.
 
Not at all. Just rest the cowl top upside down, epoxy them in place using a couple of pieces of duct tape to lock in the location, and put some weight on them so you get a good squeeze on the glue joint.

Ok. Good to know. Thank you.
Still waiting on a shipping confirmation from Vans.
 
The upper ramps installed in my 8 are without closing out either end- the outer baffle rubber is strategically cut to slide inside the ramp to provide a good seal. Never have a problem with CHTs climbing out at 120 kts, with CHTs around 380 degrees. 90 knots is not an issue unless OAT is > 90-100 degrees. Also, my CHT spread is 14 degrees across all cylinders, with #4 and #3 cylinders being within a few degrees. Also have the full height aluminum baffle in front of #1, #2 cylinders. If you seal all the leak paths with RTV, the 8 has an optimum engine cooling design point for the I/0-360.
 
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