Roller lifters= not a good idea w/stock cams

[G-E]

I don't understand why you couldn't regrind a non-roller cam for a roller profile assuming there's enough base diameter difference over the shaft diameter

it can't be any weaker if the lobe is still larger than the shaft.... that said the shaft would encounter more stress and increasing the shaft diameter might be necessary, but then it might not

[Steve88t]

It's not that you "couldn't" but rather most cams would not have enough material to do so. I am pretty certain a VG30 cam would not have enough.

Yup, just like what I was talking about in the other thread.
Sorry about that. I didn't read the last thread we had on this subject.

Well... The whole point of having a roller valve train is the ability to have a much more agressive ramp on the cam lobe. A roller lifter can follow a lobe that ramps up almost immediately. You want the valves to open fast and close fast... as fast as possible. In an ideal setup, the valve would open to it's max lift immediately, stay there as long as needed, and close immediately. You would want the valve lift to look more like a square wave than a sin wave.

There have been several variations on attempts to create just such a scenario. From the rotary ports to a custom head for a SBC that had rotating pockets in the cam that acted as valves.

I am certainly not an expert of fluid dynamics, but it seems I remember someone talking about how you have to match the opening time with what is flowing through it. IE you CAN open it too fast and cause turbulence and thus reduce velocity and flow.

But I've killed all the slow brain cells and am starting to kill the fast ones.

[G-E]

I'm pretty sure it plays an effect, you want the inlet tract to increase in airflow to overpower any prior pressure front reflections, how much this is an issue is of course very dependant on the head and it's natural flowing characteristics, there'd be no adequate way to estimate this without modelling

but you can always use your foot to work around it, like roll onto the throttle or back-blip and such

and strictly speaking what you can learn from non-turbo chevy heads doesn't lend much in the way of useful data to a turbo z31

[Steve88t]

I wasn't infering a relation. Just providing an example of ways people try to master this subject.

[G-E]

I think we're all more or less speaking as actors in a play do, half to the characters, and half to the audience