Engine Running Like 416!

[chevy400racer]

How would i be able to get my 400ex to run or pass up a 416ex? I'm getting a header for my s/o and i really don't wanna bore my quad.... but may be to a 406.

[underpowered]

depends on waht all your quad has done to it and what all the 416 has done to it. but the main difference will be the rider.

the motor builder has alot to do with how well an engine runs. my 426 would kill my buddies 440 in a straight drag, and we are both about equal in ridin skill. the 426 would win no matter who was on it. bore does help, but does not make as big of a difference as you would think. a well built 406 will stomp a poorly built 440, but honestly i have never ridden a 440 that has impressed me. if you are a decent rider, and both bikes are built about the same (other than bore) it will be close.

[khen]

I agree, from my experience the 416 and 426 bores are the best for the 400EX. I had mine set up with a 11:1 416 until I pulled the head studs, I then went to a 10:1 406 and the 416 was much more impressive. I think that was related to the compression difference more so than the bore diff though..

[F-16Guy]

There are a couple of stock bore 12:1 J.E. pistons on eBay right now. One of those and a decent cam would make a big improvement without any machine work. You would probably have to run atleast 50/50 race fuel though. You could also do a stock bore (85mm) 11:1 piston and be okay on pump fuel.