HumpinSS

iTrader: (1)

Why would you use a lobe that was slow as opposed to a lobe that is aggresive? I was always taught to get ramps that were as fast as possible to get as much air in the cylinder as possible and then slam the valve shut. If the user were using in-efficient heads wouldnt this still apply but adding duration to pop it open and hold it open longer then closing it as fast as posible? Would you still be leaving some on the table power wise by using a slow lobe?


Hope this is clear as i drank a few beers

foff667

iTrader: (2)

generally you do, but the faster the ramp rate the harder they are on springs...thats pretty much the only reason people might not want them...as you can go with a larger cam with the same wear basically.

HumpinSS

iTrader: (1)

The reason why i ask is because in teh Cam discussion thread IIRC i seen Cstraub say under certain conditions he uses slower lobes and I was wondering what the significance of that would be

LS1derfull

There is several ways of grinding lobes, first is very quick ramps,second is oversized duration in the lift curve,assymetrical, inverted, and others. Extremely fast ramps will help capture cylinder pressure, but may not rev as high with good control because of spring tension limitations. Current lobe tech. opens and closes valves with softer approaches and the rest of lobe design is where it gets hairy. You still need good spring tension for this design but at least valve bounce is less.

Cstraub

iTrader: (1)

Induction wants in and exhaust wants out. The LS1 suffers from extremely good exhaust. . .IMO its to good. Depending on what you have induction wise, the lobe could be on could not be aggressive to get the task done. As far as the LS1 exhaust, the lobe needs to be easy because the ports flow so good.

No guru here. . .just enjoy what I do.

Chris

DrkPhx

iTrader: (15)

This is exactly right. I had some ported heads flow that were very high on the exhaust (well over the 80% formula used) so I had to use a cam to compensate or "crutch" the flow numbers for optimal performance. The intake and exhaust were cut on different types of lobes with the exhaust obviousily getting the slower ramp.