hi im wondering what the differences are between the cams in the nc35 compared to nc30? (inlet and exhaust)

i have said in a previous topic about the idea of a track nc30 bike which will be purely for the track?
so what i want to know is, is there a performance increase in the nc35 which i have heard but i want me detail?
thanks webby

The rvf cams are regarded as superior, the exhaust cam has a different profile and the inlet cam is different also (diagram below), both are a slight evolution of the vfr cams. According to honda press relases of the time the rvf cams are also hollow which would assist efficiency and reliability (anyone weighed them?).

The rvf heads are also superior to vfr for race applications, might as well bolt them on at the same time.

I doubt that you'd notice any difference bolting the rvf parts onto a vfr engine, but for serious race applications every little bit helps.

Aren't VFR exhaust valves marginally larger than RVF ones? Does that have any bearing on the performance difference?

speedy231278 wrote:Aren't VFR exhaust valves marginally larger than RVF ones? Does that have any bearing on the performance difference?

No, the rvf exhaust ports are a narrower diamater, the valves are the same size in both models.

If the valves were larger in vfr's they would be the obvious choice for racing (high rev) applications, however the rvf heads are the ones to go for.

Some great info on Mike Norman's site (under 'ports' section): http://mngforce.typepad.com/nc450vdev/n ... st-go.html

I am fitting RVF cams to my road NC30, have spoken to Rick Oliver about it and he said there will be an increase in power due to the advancements with the camshafts, and also like Cammo says they are hollow which will give further improvements.

My only gripe with fitting RVF heads aswell is i was under the impression that the NC35 made less power new than the 30, I have been doing a bit of searching on this and it seems to be true to all japanese 400's made less power after 1994/95.

Peak power figures for various 400's
VFR400R 59bhp Vs RVF400R 55bhp
CBR400 NC23 59BHP Vs CBR400 NC29 55BHP
GSXR400 Gk76a 59BHP Vs post 1995 Gk76a 55BHP


So i dont know if the lower peak power has anything to do with the smaller intake port size, or if it is in the carbs, ignition, somewhere else. But the RVF undoubtedly has a better midrange which unless i am mistaken is down to the "improved" carbs and camshafts??

So this leads me to beleve that the peak power is strangled mostly in the narrower intake port diameter, and the better flow characteristics of the 35 heads and carbs are to improve the midrange, so my thinking is that fitting the advanced NC35 camshafts to NC30 heads that have the bigger intake port diameters and larger carb diameter will give an improvement to BHP.

I am really searching for some hard proof on this for example dyno's on a VFR with full RVF heads fitted and then on a VFR with just the RVF camshafts installed. But for now i am going to be fitting NC30 heads with just the 35 camshafts unless there is an overwhelming opinion to fit the newer heads too.

This is my 2 pence worth, rvf's make more power once fettled for racing that's a fact. As said above the rvf is a evolution of the VFR and development had moved on, personally I can't see the point in swapping in the rvf cams for very little benefit it might give you've just ruined a rvf motor. Honda put some serious R&D into these bikes and IMO all the changes they made to the rvf motor are designed to work together, ie if you want that bit more power then just swap in the complete rvf motor.

VFRkieran wrote: My only gripe with fitting RVF heads aswell is i was under the impression that the NC35 made less power new than the 30, I have been doing a bit of searching on this and it seems to be true to all japanese 400's made less power after 1994/95.

Peak power figures for various 400's
VFR400R 59bhp Vs RVF400R 55bhp
CBR400 NC23 59BHP Vs CBR400 NC29 55BHP
GSXR400 Gk76a 59BHP Vs post 1995 Gk76a 55BHP


So i dont know if the lower peak power has anything to do with the smaller intake port size, or if it is in the carbs, ignition, somewhere else. But the RVF undoubtedly has a better midrange which unless i am mistaken is down to the "improved" carbs and camshafts??

Recently had this discussion elsewhere. In the late 80s to mid 1990s it was fashionable in Japan to 'limit' vehicles in certain classes to certain power outputs. On paper, the 400s were all 59/60bhp until about the date you quote, then lost 6bhp when the agreement went from 59/60 to 53. The change in the head might be a factor, but in my ignorance I can't see a tiny difference in the port diameter robbing 10% of peak power. All high performance cars made exactly 280bhp, regardless of engine size or type. However, what the paperwork said and what the vehicle produced tended to be rather different.

2mm in carb diameter is actually quite a significant reduction in area, can't be bothered to work the figures out atm but wouldn't be surprised if it was circa 10% reduction

Pip

Well, yes, but at the same time, some people use RVF carbs on VFRs, don't they? It's not all about sheer size, if that really is actually the case, or people wouldn't use smaller ones.

Edit: just done the sums. Excluding the obstruction caused by the butterfly valve, a 32mm throttle body has an area of 802.25mmsq. 30mm equates to 706.86. That's an 11.9% reduction, which is quite a lot!

The 2 carbs despite looking similar and being interchangable are actually quite different. For all out power the VFR carbs are prefered but for anything else RVF carbs are better.