Hi Randy, You are correct. The Thunder Tiger on hand has your venturi, spray bar and NV, but not the JR 15 marking. The photo is one of the three OPS 40 on hand. Two of which are yours. (JR 15 and RANDY 49)
The OD of all three OPS liners are visisble at the exhaust and are brass colored. I suspect none are AAC. How did they run? I don't recall many OPS powered stunters. Maybe some of the early piped models??
Hi Jim
They run well either way, as long as they have the proper size venturi, I setup a boatload of the OPS SPA RE 40s both AAC and AAC, They were the second strongest of the pipe 40 engines,
I ran them late 80s untill about 1993, then the PAs replaced them
People like Bill Werwage, Bob Hunt, Rob Hunt ,Bob McDonald, The BEAR , Frank McMillan, and dozens of other used the 40 SPA in their stunt ships
Randy