Hi I am looking at getting some exhaust pipes made for cat 30s but I don't know what size or thread they are, regards Andrew

The threads on my early Thirty are 2-1/2" NPT threads. I bought a pipe tap to clean the threads.....inserted a 4" long threaded on one end piece of schedule 40 pipe and used a 1/8" wall piece of pipe clamped to it through the canopy. I did this to cut down on weight on exhaust manifold.

Just my thoughts......Bill

Cysco is correct on the thread and I like his idea for reducing the weight on the manifold as many of them are very weak at this point in their lives. S-756 for rear seat model with canopy top and top control without canopy to is 2 1/2" standard black pipe 24" long. S-1768 for top control with canopy is 32" long. R-265 for rear seat model without canopy has two different lengths. The print has a change on 11-30-26. Before that date it is 12" long and after that date it is 14" long.
Thanks
Ken