High Cylinder Head Temperatures

October 1987

Bob Hansen, 0-235 Long-EZ builder/flyer, has had high CHT's since day one. He says he has tried every suggestion in the Cps and many ignore to not much avail. Finally, in desperation, he cut two "reverse" scoops on top of the cowling with the leading edges pointing between the two cylinders on each side (see sketch). His first test flight after this operation was a pleasant surprise, 70 to 85 degrees of temperature reduction at cruise.

Bob's Long-EZ is equipped with a stock TASK cowling, has a NACA flush inlet with 45 square inches of inlet area, a 3" prop extension and an 0-235-L2C engine. Since Bob's success, fellow Sedona resident, Gordon Diehl, cut smaller openings in the top of his cowling (I"x3") and he saw a 50' reduction at cruise. Of course, this amount of temperature drop is at cruise and is only about 1/3 as good in a steep climb since it is so velocity dependent.

Test results: CYL #1 #2 #3 #4
Previous best: 420� 450� 460� 425�
After cowl cutouts: 350� 380� 375� 355�

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