performane difference between 700 and 750 2nd gen

Does not mention any differences between cam lobe location, or journal measurements.

They do identify the differences for the camshafts between FR, RR, IN, EX with engraved markings. But thats just so you put them back in the correct position on reassembly

 

Camshafts actually define an engine provided all other parts mate to it. You can take two identical engines with the same cam specs as far as lift, dur, lca, ica and cam lift and have two different power out puts(hp,tq). It's all in how the cam maker designs the flanks of the lobe and the rate at which the valves open and close. It's called the lobe profile.

Talk to a cam designer and the lobe profile is what they really don't discuss much. Cause that's their edge over other designers. Here's a little blurb on it.

"Camshaft Design.

Camshaft design today is an extremely complex process employing the use of computers in every phase of design analysis and testing not to mention the years of experience required to make these phases become reality. As complex as it is however, camshaft design, in its simplest form, may be broken down into two segments.

The first segment involves lobe placement on the camshaft. This establishes the very critical valve train event timing in relation to piston and crankshaft positions. It also establishes the displacement or separation of the intake lobe in relation to the exhaust. This placement is very critical and must be exactly the same for each cylinder. Lobe placement is one segment of the camshaft design experience that relies heavily on the designer's experience. As you already know, you may advance or retard the camshaft in the engine, but altering the displacement requires a new camshaft.

The second segment involves designing the lobe and clearance ramp profiles. By far, this is the most critical and difficult segment of camshaft design. In today's race engines you must develop a lobe profile that is aggressive enough to produce the desired rate of lift yet smooth enough to avoid new valve train problems. You must walk a very thin line here to take advantage of the attainable high R.P.M. power available with today's cylinder head designs, yet not lose it all to stress, deflection and failure of the valve train. More recently, significant power gains have been found through several new approaches to clearance ramp profiles.

Obviously the computer has become a most valuable tool in all design applications from economy camshafts to the most sophisticated of race designs. But the computers and all the programs would be useless without the experience to back up a total design effort. It's the optimum blending of engineering, years of design experience, technology and communication that offers the Cam Techniques competitive edge."


So once you decide how much and at what rpm you want to make power/tq you start your engine build with the cam and pick parts (heads,induction etc) to optimize the performace you want.

You can take your current cams and advance them 4-6degrees and get more low-mid power and lose a little top end. Or do just the opposite and lose a little bot-mid range with more top end IF the heads/induction can handle it. I learned that the most important cam event that good designers start with is the intake valve closing point and they go from there. That's what basically sets what your dynamic compression is going to be. Which is what the engines sees vs static compression.

You can also change this some what by the rocker arm ratio on the same cam. Lets say a cam with .300" cam lift (base circle) with a 1.5 rocker ratio will lift the valve .450" vs a 1.6 ratio rocker at .480". Along with the added .030" lift you will have a little more overall duration. It's all part of tuning an engine. Of coarse you can really screw things up if you don't do things smartly.

 

The Black Art of Camshaft Grinding!


"My wife has a better pair of tits than yours does, but I cant let you see 'em":boobies4:

 

What's the weight difference between the 700 and the 750?

 

That's a good question which may not be answerable. I have looked for Honda cam specs for several years now. I haven't found any published listing by Honda of all of their cam specs for any cam they use. They do give bits a pieces in different areas of their manuals. Like LCA is 108* same for the ICA for my 83 750. They have valve open/close event numbers and I think I read the rocker ratio is a 1.7. You can tell the cams have very good open/close ramps by the lash they run.

There are a couple of cam grinders that Invisiblecities has pointed to in the past that should know. Just because they are the few that grind Honda V motor cams. They do give a couple of more cam specs than what I've found else where.

The neat thing with separate cams is you can change the ICA and the LCA characteristics vs a cam with ex/in lobes on the same stick.

 

I must be missing something.

How can a 50cc increase add up to 11hp ??

The seat-ot-the-pants dyno can't be relied upon in this case: for example, what were the compression numbers on the 700 vs. the 750 ??

 

We used 108 deg on cam centers on our 2 valve DOHC suzuki when racing. Made a lot of difference at higher rpm. It was a pretty easy adjustment, involved slotting the chain rings.

11 hp difference, I think it is possible. On a displacement difference, there is 7% more or about 7 hp so with different cams is 11 hp possible? My butt dyno says that there is more in the midddle. The top end is harder to judge.

 

Megacycle Cams