All you 300 guru's

[TRX-330]

Ok i need your guys help, im planing a major engine build this winter if all goes as planned. I want to know if i can use a 400ex rod for a stroke on my 300ex or would the 300ex cranks be too small, if so could i use a 400ex crank? also what would i have since the stroke would be longer? will the cylinder need to be modified? Also for a big bore since i would be useing the 400ex rod would i be able to bore the jug to fit a 400ex stock sleeve and piston? How far can i go with bore size cause id like to if i can use a slightly bigger 400ex piston. With all this said can i put a 350x head on? to acount for the bigger opening at the top where the valve's are? Im just trying to do something major for next year. BTW im in school for small engine so i have all the tools and teachers years or experience to help me.

[bwamos]

Originally posted by TRX-330
I want to know if i can use a 400ex rod for a stroke on my 300ex or would the 300ex cranks be too small, if so could i use a 400ex crank?

No, and No.
The rod won't change your stroke anyway. The radius of the crank determines that. The Rod only moves the location of the piston. A 400ex rod wouldn't fit anyway, but even if it did it yould only slam your piston into the cylinder head.



also what would i have since the stroke would be longer?
will the cylinder need to be modified? Also for a big bore since i would be useing the 400ex rod would i be able to bore the jug to fit a 400ex stock sleeve and piston? How far can i go with bore size cause id like to if i can use a slightly bigger 400ex piston. With all this said can i put a 350x head on? to acount for the bigger opening at the top where the valve's are? Im just trying to do something major for next year. BTW im in school for small engine so i have all the tools and teachers years or experience to help me.

You cant use 400ex parts or 350x crankcase parts in a 300ex. Different I.D./O.D.'s just plain not compatible. Your options are really to swap out an entire 350x engine, or get the 300ex stroked, but you cant get much more stroke out of the 300ex anyway since it is already a stroked 250x.

Your best bet is to simply overbore the engine and get the head ported to match w/ flow bench testing.