Topic: CB750 Cam Lobe Lift vs Valve Lift

[Hinomaru]

Been looking into 69-76 750 K aftermarket cams and both Megacycle and Web advertise valve lift not lobe lift. Dynomans DP series just provides a "lift" number and now I've hit the wall of confusion.

Take a Web #41 cam with a lobe lift of .328 and the advertised valve lift of .360 (Numbers provided by Web)

I'm assuming the difference must be in the rocker arm ratio.

If so, what is the stock rocker arm ratio?

If not, where is the .032 difference coming from?

What am I missing here ...

[MRieck]

Been looking into 69-76 750 K aftermarket cams and both Megacycle and Web advertise valve lift not lobe lift. Dynomans DP series just provides a "lift" number and now I've hit the wall of confusion.

Take a Web #41 cam with a lobe lift of .328 and the advertised valve lift of .360 (Numbers provided by Web)

I'm assuming the difference must be in the rocker arm ratio.

If so, what is the stock rocker arm ratio?

If not, where is the .032 difference coming from?

What am I missing here ...

Web #'s leave something to be desired. I t has nothing to do with rocker ratio's etc.

[Hinomaru]

MRieck, thanks for the sanity check! 

 

[BLUE71TURBO]

 You should call WEBCAM and talk to them. They are great people. I'm running a custom made WEBCAM in my turbo bike.   

[Hinomaru]

Blue,

I did call them and those are the lobe lift & valve lift numbers they provided me with over the phone and in a follow up email. There seems to be some confusion over at Web as to the correct lift number, so there won't be a # 41 grind for me...

  

[MRieck]

Blue,

I did call them and those are the lobe lift & valve lift numbers they provided me with over the phone and in a follow up email. There seems to be some confusion over at Web as to the correct lift number, so there won't be a # 41 grind for me...

  

In honesty the 41 does very little in regard to performance.

[Big Jay]

If you have both numbers you should be able to figure out the ratio.  I remember "back in the day" when one racer discovered that there was a slight variance in the ratios, rocker arm to rocker arm. He made a gauge that he could measure them. He would go to Honda dealers and have the parts guys get all of the rockers out, and he would go thru them looking for the ones with the best ratio.

[Sam Green Racing]

Belive it or not, I know a guy that did that with a bearing manufacturer, he had them send him thousands of rollers and about a hundred races, he would measure them all and pick the ones he wanted.
I think it's called taking blue printing to a new level. He is a world authority on the particular motors that he builds, wether or not he put that much effort into all the motors he built or just the ones for his own use, I don't know but his motors are world renowned for being faster and better than the factory race motors of the day.

Sam.

[turboguzzi]

Belive it or not, I know a guy that did that with a bearing manufacturer, he had them send him thousands of rollers and about a hundred races, he would measure them all and pick the ones he wanted.
I think it's called taking blue printing to a new level. He is a world authority on the particular motors that he builds, wether or not he put that much effort into all the motors he built or just the ones for his own use, I don't know but his motors are world renowned for being faster and better than the factory race motors of the day.

Sam.

sounds like tony scott

[Sam Green Racing]

 

[BLUE71TURBO]

 I'm really surprised that nobody ever made high ratio rocker arms for the honda. Like in the high performance world of VW drag cars.
 I use to run ratio's of 1.25, 1.4, 1.5, and 1.6 . The best rocker arm assembly's had needle bearings .