+1mm valves

[Stroker81]

I am thinking about putting +1mm valves in my 440 when I port and polish it here in a few weeks. What are the advantages or the +1mm valves. Also where is the best place to buy them and what is the best valves to get?
Thanks

[rideracelivemx7]

well i was going to do them when i did my crf450 build and the machinist said they do so many 450s that they dynoed before and after and he said you loose a good amount of torque, so if you want to beef it up with a stage 1 cam and high compression i say go for it, but i belive bigger valves is to acheive higher hp numbers isnt it? stage 1 cam is for lowend so you might see about the same hp rating as you have now

[drew416ex]

Originally posted by rideracelivemx7
well i was going to do them when i did my crf450 build and the machinist said they do so many 450s that they dynoed before and after and he said you loose a good amount of torque, so if you want to beef it up with a stage 1 cam and high compression i say go for it, but i belive bigger valves is to acheive higher hp numbers isnt it? stage 1 cam is for lowend so you might see about the same hp rating as you have now

But that was on a 450. Not saying it wouldnt be the same on the 400 but they are two totally different engines. I got just the intake oversized. I was told by many different places that they get better numbers just doing the intake. I dunno. I used kibblewhite stainless valves and they have held up great.

[Sanddraging28]

i have over sized valves in my bikes....my machinist say that on a 400ex +1 mm valves make the head flow much better, put that with a good port and polish job you should be golden. just make sure you add a bigger cam to take advantage of the new flow of the head,and and this might be a goo time to get a full exhaust to go with the P+P. i saw an almost 4 hp difference on my 426 on the before and after dyno's. i went from a stage 2 HC to a P+P and a mega-cycles cam. i use the kibblewhite black diamond valves.