Camshafts, idle quality, driveability and LSA-REAL WORLD EXP and OPINION

It amazes me that guys who have been doing for so long, still think LSA is something you change in SPITE of all other factors.

All of th cam guys I deal with, to a man, the last thing we discuss is LSA. I've said it before, you can't isolate just one function and focus on it like we are talking. Myopathy is bad.

So let's see if we can set up at least a few cones to mark the boundaries.

The first basic thing you need to know is displacement. Then RPM. Then you need to see how the head flows.

Once you have those basics, you can start to make sensible cam timing events. You damn sure won't need the same duration for a 632 as you do for a 572 (considering RPM).

Would an engine that needed 300 degrees of duration to make 7000 RPM with a head that flowed 340 CFM with a port volume of 260 cc's still need that much duration if the head was increased to 280 cc's and flowed 400 CFM?

Not if you wanted to keep the engine speed the same. Right now, we barely have the duration for the intake lobe, let alone looking at exhaust, overlap, reverse flow etc.

Once you have the intake lobe figured out, you have to do the same with the exhaust. And maybe, after you lay out the exhaust, you realize that you need to change something on the intake lobe. And yet, LSA is not even discussed.


Somehow, some people on here think I have said that a narrow LSA is the do all be all end all. I've never said that. I have said, that with certain parameters, I can say the LSA is too wide.

There is no such thing as a narrow LSA or a wide LSA.

Then we can discuss single verse dual pattern cam, symmetrical verses asymmetrical lobes, God forbid we discuss inverted radius lobes. We can discuss split overlap etc. All of this comes BEFORE we ever need to discuss LSA.

When we get to LSA, if we want to make it wider, do we advance the intake lobe or retard the exhaust lobe? Maybe we split the difference?

This is just the TIP of what I discuss before I order a cam. If what I have in my head is different from that the cam guy thinks...then there is a long discussion and sometimes I actually get the actual timing from them and plot it out so I can see it myself.

That's why I stopped picking cams long ago. But neither do I just give the cam guy carte Blanche to do what they want. I want to know exactly what I get before it gets there.