Exhaust Repair

I just finished another 100hr service. I changed the oil and filter, cleaned and gapped the spark plugs, and fixed a broken nut plate on the baffling. While I had the cowl off I noticed an exhaust leak around the #1 cylinder. This cylinder has always been a problem to get sealed, but last time I thought I had found the magic combination of copper gaskets.  Bummer. I pulled the exhaust and noticed that the tabs at the collectors were starting to crack.  

Spark plugs as they came out of the engine.

I put the headers in the vise and filed the flagged flat. After checking them with a flat gage block, I lapped the surface with a stone to make it smooth.   

A finished flange

Next I decided to cut off the old tabs and replace them with a better system.   

ProFab is a local race fabrication shop that specializes in exhaust systems. They always have 321 stainless and nice fittings. I stopped by and picked up some tabs and springs.  

After prepping the weld area and cleaning everything with acetone, the end of the tube are taped up to be purged with argon.  

I got a new #12 Furick cup for the TIG. It shields the weld much better than a conventional ceramic cup. It will drain a bottle quickly though at 30CFH! 

Here was the first pass.   

They weren't all that pretty though. Here's the finished set of tabs with the spring installed with 3/8" of preload. I put a spring in each side of the collector, which is much better support than it had previously.