Discussion Starter · #1 ·
Hey everyone! So I just rebuilt the top end on my 05 400ex. I bored it to a 416, ported the head, new valve seals and a new cam. Got it all back together and fired it up and was running amazing across the yard for about 3 minutes and then it just started blowing smoke like crazy out of the exhaust. Any ideas what the problem could be here? I'm stumped because I checked everything when I had it torn down and it all looked perfect and all went back together perfect. Thanks in advance for any help!