Englewood is around 5300 feet. Have you had your cat checked yet? My CJ is registered in Estes Park and does not run a cat anymore. Just a 3 inch single using the stock manifolds. Like I said, the bottom end is SO strong in this thing. I can go around a corner and not need to downshift. With the T-18, it easily pulls out of corners at 800 rpm in 4th gear and effortlessly accelerates with the 37" MTRs. The 360 would struggle. I had a buddy several years ago that ran 401s in his CJ, and ended up with a 272 cam. We even ran it at Bandimere where it ran the 1/4 in the high 15s at 80 MPH with a T-18, 4:10s and 33s. It would see well over 6000 RPM, and he pushed it to 7000 on a snow run when his rev limiter was bumped up to 7200 unknowingly. It grenaded shortly after that. He went through three 401s and grenaded each one before going back to a 258. My personal feeling was they were too radical and didn't like the extended high RPMs he was pushing them too. I'm sure there are 401's that last at 6000, but not without modifying the oiling system. I'm getting side tracked. Bottom line is I wanted a strong bottom end engine and got one.Originally Posted by shimniok