Cam Specks

[marty]

In the F.A.Q. "drop in cam" post I found some numbers that don't make sence. Two people said the stock 400EX cam has durations of IN. 234 & EX. 238 @.050" And the XR400 has IN. 240 & EX. 244 @.050". Honda says 400EX IN. 225 & EX. 225 @1mm and XR400 has IN> 232.5 & EX. 230 @1mm. Since @.050 the valve is opened more and the cam had to turn further to reach .050 valve opening, and when closeing it reached .050 sooner than 1mm the duration should be shorter if you rate it at .050 instead of 1mm. I'm not saying anything bad about anyone, and we all appreceate each others posts or we would not come here. If someone can clear this up that would be great. Also where did the specs @.050 come from when honda dosen't rate them like that? Thank you all for all your time, knowlage, and input. This forum is great. Sorry for the large can of worms and thanks again. Marty

[marty]

Anyone?

[MIKE400EX]

Marty,
I believe I was one of the people that posted the specs you refer to that give duration @ .050". Those came from a very reputable cam grinder. You are correct in that ratings at 1 mm should be greater than those taken at .050" on the same cam. Many aftermarket cam grinders rate their cams @ .050", which is probably since most automotive cams from the US are rated that way. There's probably as many different ways of measuring cams as there are cam grinders. I don't recall ever seeing posted numbers from Honda, but would be more inclined to believe them. You wouldn't want to bet the shop on those numbers but they are close enough to be invaluable when spec'ing out a cam for a given application. Especially for the majority of us that don't have the time or resources to buy a variety and test until we are content. LOL, although that WOULD be fun!

[SnellCRP]

Honda measures everything in mm not inches. Thats why the # were different just convert 1 mm to inches, 1mm = .03937inches.