I took the the opportunity while I had the engine apart to upgrade the DD cooling box.

When I originally made the Down Draft cooling box years ago, it was completely made of fiberglass/carbon with small Al inserts to reinforce holes. This approach didn’t work so well as you can see because the heads would get up to 400-450f and was destroying the glass/Alum attachment points. I could never properly torque the bolts and they were always loosening up on me.

The fiberglass is just disintegrating!

I have been an advocate lately that one should use Al where appropriate and easy to incorporate, and not use glass in high temp areas. The decision was made to make a hybrid DD cooling box to smartly use Al on the heads and glass everywhere else.

The DD cooling box was cleaned in my dish washer. A couple of wash cycles sure cleaned things up!!

template was made to cut out the Al replacements for the head area.

The parts were cut out in Al.

Here you can see the old and new head attachment areas. I really like the new style head attachments as the bolts can be properly torqued and the Al can handle the high heat of the heads.

New paint and the rebuilt DD box looks good and will now work for the life of the plane with no issues.