Exhaust Manifold Heat Boxes Completed

With the shell finished the next part is the outlet tube.  This tube has a 2" outside diameter and 1".  The easy thing would be to cut it from 2" tubing, but I didn't have any.  One source for tubing is the pieces of exhaust pipe they sell at the the auto parts store.  For me it was easier to just roll a strip of 1" steel into a tube and spot weld the joint.

I find it easier to start forming the tube at the ends.  The middle is always easy to form because you have the leverage of the long strip to bend it.  It turned out that a 1 7/8" hole saw was the right size for the spring back of the steel.  I used it to form the first 3/4" of each end of the strip with a light hammering.

Then I rolled one end of the strip about half way around the saw.

Then I started from the other end of the strip and finished the tube.

I needed a fixture to hold the tubes while welding so the Outside diameter would be a consistent 2".

I used a 2" hole saw to cut a groove about 3/8" deep in a piece of 3/4" plywood.  The tube on the left is in the groove, the one on the right is setting on the board.

I made 2 welds near the edge of the seam, then flipped the tube in the jig to make 2 welds near the other edge.  I added 2 more welds in the middle.

The last piece is the baffle.  I used the same block from the flanges on the shell to form the weld flanges on the baffle.

A left and a right are formed from the same blank.  I used the hole saw to form the bend around the outlet hole.

I found it easier to spot weld the baffle to the shell before welding on the outlet tube.  The clean metal welds better.  I also wanted to weld the ends of the flange to the shell, for a little extra security, while welding on the outlet tube.

I used 4 spot welds on the long side and 2 on the short side.

The outlet tube is a snug fit to the hole.

Before I welded the tube I was eager to see how all this fit to the manifolds.

I like it.

 Here is the finished heat box after all welding and sand blasting.

I like the more rounded corners.

I think the baffle will do the job of give the air a little more heating as it move to the outlet.

Now I need to weld them to the manifolds.