Has anybody tried to cool down a 3300 with louvers added to the cowl?

Views: 587

Reply to This

Replies to This Discussion

I've extensively researched 3300 cooling and never found that anyone had much luck with louvers.  The 3300, being a 6-cylinder, air-cooled engine in my STOL 750's low-speed, high drag airframe, was initially a challenge to effectively cool but I've now got it in the mid-upper 200's F!

Here's a list of cooling enhancements I did:

  1. Extend lower cowl lip additional 2" (mine was 1" originally)
  2. Made inlet ramps between cowl and ram air ducts..
  3. Put "butterfly" cooling baffles on underside of cylinders.
  4. Installed end plates between cylinders to keep cooling air from spilling out between tappet covers
  5. Extended rear of right ram duct down and around backside of #5 cylinder.
  6. Meticulously sealed ram-air ducts to cylinders.
  7. Installed ducted sump cooler using bleed air from ram-air duct - lowered oil temps 10-15 degrees F.

Probably not all of these were necessary, but it got to be a "mind game" with me as to how low and how even I could get the cylinder cooling!  Most of these tweaks are described in either the 750 or Open forums - just do some searches.




Wow, don't know if I understand (without a picture) what some of your mods are.  My 601XLB is a 2006-7 Kit, and 3300A was bought in 2009 with the cowl from Jab USA.  I installed engine and cowl (airducts) per Jab instruct at the time,  about 2010.  Followed their directions carefully, but still have temps all over the place.

Most of my temps are on the higher side with a spread between low and high of nearly 100 deg.  none of the factory recommended mods seem to make much difference.  Hence, the thought of louvers.

Lower cowl lip came with a 2" lip.

Inlet ramps between cowl and air ducts???????

"Butterfly" cooling baffles on underside??????

End plates between cylinders???????

Understand extending ram air duct down.

Can you determine which of your mods was most useful?

Can you send some pics of your mods...

Thanks for response.



1. Extended cowl lip:

2, Inlet ramps:

3. Butterfly baffles under cylinders:

4. End plate baffles between tappet covers:

5. Extension of rear of right ram air duct:

6. Meticuous sealing of ram air ducts. No pic, but self explanatory!

7. Ducted oil sump cooler - Zenith had a kit for this, but it introduces additional high pressure air in the lower cowl and that upsets the ram air high pressure/lower cowl low pressure differential and can make cylinder cooling worse. My design (below) "borrows" some high pressure air from the left ram air duct ( which was the coolest side) to cool the finned oil sump. Lowered oil temps 10-15 degrees F, which lowers heat burden on air cooling of cylinders:

IMHO you can accomplish whatever lower cowl negative pressure needed with a sufficient lip extension - I've got 3" total.  I've never heard of louvers making any significant difference.

It's hard to say what helps most.  First extend the lip another inch for a total of 3" and meticulously seal the ram air ducts and add the end plate baffles (and extend rear of right ram air duct if #5 is hot, which it usually is). This will get every bit of cooling air through the cylinders and out the lower cowl. Then, add butterflys if necessary.  These are all easy and cheap to do.  If oil temps are high, make the ducted sump cooler - very inexpensive and very effective.

Here's some links:



Some searches with key words in the Open and 750 forums will probably turn up other topics with details.  

Hope this helps,



Really appreciate your pics.  Thanks for the input, I'll get on it asap.  Seems like the louvers would also help, but I'll use your suggestions first.

Thanks again,


I see you are flying a 601 with higher cruise speeds than my 750, so ? possibly ? the louvers could help. I personally would want to try some of the other mods before cutting into my cowl, but who knows, it might work better with your faster speeds.  If you try the louvers, by all means report back and let us know how it turns out!



New from Zenith:

Zenith Planes For Sale 

Classified listing for buying or selling your Zenith building or flying related stuff...


Weather Maps

Custom Instrument Panels
for your Zenith

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, power distribution panel, Approach Fast Stack harnesses, Dynon and Garmin avionics, and more.

Custom Upholstery Kits for your Zenith Aircraft:

Zenith Vinyl Upholstery Kits

Zenith Apparel from EAA:

Zenair Floats

Flying On Your Own Wings:
A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

How to videos from HomebuiltHELP.com

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit HomebuiltHelp.com for the latest DVD titles.

Aircraft Insurance:


West Coast USA:

Pro Builder Assistance:


Transition training:

Golden Eagle Aviation

Pianosa Flying Farm

Aircraft Spruce & Specialty for all your building and pilot supplies!

© 2020   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service