I have the same engine with the same problem. My engine was delivered to me in Dec of 07 and I am under the impression that I have the updated carb however I am trying to confirm that. I am using the OS P3 plug. I have tried the regular trouble shooting even changing out my fuel tank but nothing helped. This past weeked I replaced the carb with a Nova carb and it seemed to hold a tune much better but I wasn't able to race it. I won't know for sure if the tuning problem is gone until I get a good 5 -7 minutes out of it. Prior to my switching, the engine would run good for about 3 minutes and then start acting up. Going back on to the track on Wednight for some test and tune so I will be able to see if the engine likes the Nova carb better. I have my fingers crossed.
I was in the same boat, run great for 3-4 minutes, then start acting up, mainly the temperatures would climb to the 280’s. So, I swapped the carb for an OS unit, and now I have had zero problems. This is my first GO engine, one other person at my local track runs a 07 21 5 port turbo, and it screams, not to mention the run times. Some of the other racers look down at the GO engine, but after the last race, most of them are second-guessing themselves. I TQ’ed and first in the A main. I cannot say that the GO engine does not have its problems, but I think I will stick it out and see what happens. Just hope it runs as well with the new updated GO carb when it gets here.
