Largest Size engine in a chief?

[Attexnoob]

I just bought a 400 chief, but the engine it came with (400 ccw) just wont idle while it is warm or after a while of running it, also the left cylinder just keeps fouling out and i have to change the sparkplug every few times. Anyways i was woundering if i could fit a 500 superchief engine without any mods

[Don]

The bolt pattern on the 500 will be different, so the mount will have to be modified. Otherwise, they're the same basic machine (Superchief wasn't made until the body was changed over to HDPE, but that won't make a difference).

Good luck.