Well as of yesterday i was pretty sure i was going with the 426.... but the more i read, the more i am beginning to be weary of the heat issue! I do not plan on re-sleeving because of the $$ difference, so i was wondering if a 426 would be too much on a stock sleeve? walls are a little thinner, and i dunno how much difference that will make?? How much performance am i gaining with the extra 10cc's, and how bad would i be cutting into my reliability?? Any help will be greatly appreciated...

 

the closer you are to stock size the less the chance of overheating. and the 400ex's are air cooled, makeing them even more susceptable to overheating due to there large cc size. i do know if you go to the 440 kit your relyability is shot, so you should just race it then. if you go to the 416cc kit there should be a smaller chance of overheating than a larger kit.

anyway i see your list of other mods, like a stage 2 cam. if you go with a stage 1 cam i know your relyability wont be hurt that much. the cam swap is gona help you more than the 16-26cc's anyway.

 

I toltally agree with cherokee99 on this issue i would keep the bore as close as possible , even better if you could afford to replace with a new cyclinder keeping it stock ; but if can't afford a new cyclinder i would go with the smaller bore and keep the reliability of the stock engine !

Goog luck to you reoredrider08 , and welcome to the forums !............

 

if you plan to spend a little bit of money into your 400 definitly take a look at the curtis sparks website. they have a build kit for a 416 big bore and it is sick!!

If your not trying to spend much and your worried about overheating, i suggest keeping stock bore with an 11:1 weisco piston. also if your valves are in good shape add a stage 1 hotcam. (which is fine with stock valves and rockers)

Thats what i did to mine and it picked up crazy mid and low range power.

 

o! on the subject of rebuilding your 400ex- spend the $20.00 and have your valve seats replaced! even if they are not worn out its a good idea to replace them- i mean you already have your engine apart. i havent heard of any problems with the replacement valve seats, but its a common occourance on the 400ex's for the seats to wear, shrink, or even fall out eek! but iv only seen one engine where they fell out so its not likely. but its something you should do, wont hurt your mechine