Toda only makes one set of Spec B cams and it does not have stock primary/secondary lobes so that comparison is a bit moot.

In general a cam profile is only good to a particular RPM. Generally you put the VTEC crossover at the point where the power curves intersect for each profile (primary/secondary and mid). If you have stock primary/secondary lobes and a bigger-than-stock mid lobe, you move the point in the RPM band where the mid lobe profile becomes effective but do not extend the range what you get is a flat spot. If you leave the VTEC crossover where it is, you get off the primary/secondary profile before they can run out of juice but you're out of the optimal range for the mid profile. If you move the VTEC crossover up to where the mid profile starts breathing then you stay on the primary/secondary lobes for too long. Either way is less than ideal.

I can't think of a decent performance-oriented reason to retain the stock primary and secondary lobes. Their main purpose is to keep the motor from falling on its face before you hit VTEC while at the same time keeping fuel consumption to a minimum. If you want to see the most worthwhile increase in power you have to go with a cam that is designed to greate power both before and after the cam switchover.

 

So when under vtec the stock primary/secondaries will make more power then the one with (bigger than stock primary/secondary)? If i do get a cam with stock primary/secondary, I will develope a flat spot? right before the vtec lobe kicks in? But the flat spot usually doesen't last that long about 500rpms? So basically on first gear my launch will suffer a bit? Will a cam with a stock primary/secondary along with a agressive vtec lobe like skunk2 stage 2 or toda bspecs do good on a street? Is it all that bad with the stock primary/secondaries? If I did have a race with someone that has the exact same cam but just without stock primaries/secondaries, What would happen in the whole race? I start out quicker and he'll beat me in the end? thanks again

 

If you have a severe mis-match of grind specs between the primary and secondary lobes on a VTEC engine, your "flat spot" could be huge. Thinking worst case scenario: you could potentially have a gap so large that the engine would be unable to continue gaining RPM after the VTEC crossover.

It really is for the best to go with a slightly hotter primary lobe grind to more effectively match up to the characteristics of your secondary lobe. An ideal power band really is seamless between being in and out of VTEC, I can't understand why anyone would want a harder "hit" or a bigger step. It costs you more rev time than helps your acceleration, even though you will certainly keep your stock idle and have the potential for higher peak numbers, you also have the potential for a slower setup.

 

True it makes sense to have a cam that has the primary/secondaries matched to the vtec lobe. But which cam will give a good idle at the same time whip some ass on the street? JunII,III, Toda b,cspec, Skunk2 stage1, 2,3, and Crower, etc. And is it true you can still use stock valve train with Jun cams? let me know what you think. Thanks a lot