Cams for 455 engine builds.

[gtofreek]

Wide lobe seps are not considered old school. There are engine combos that need them, or run better on them. Long stroke engines can benefit from them to keep the engine in a wide power band to pull the car. Engines that need to make power at 9000-10,000 RPM's NEED wide lobe seps[sometimes as wide as 119°-120°], and big duration cams. Narrow lobe seps run out of steam too soon to make power up there.

We all know that narrow lobe seps make more peak power than wide lobe seps, but do it in a narrower RPM range[when compared to the same lobe ground on a wider lobe sep].

We all know that wider lobe seps make less peak power than narrower lobe seps, but in a broader RPM range. More average power. Certain lobe designs, by nature, benefit from wide lobe seps, while other lobes benefit from tighter lobe seps. If you have a lobe design that when ground on a 110° LSA, has a power band as broad as another lobe design ground on a 112° or 114° LSA, why not take advantage of the extra power if your not running the cam out of it's power band in the first place?

As far as dynamic compression is concerned, well, IMO, you can throw those calculators out the window. They have no real place in engine building. They are just a computer program someone came up with because they had an idea that sounded logical. They DO NOT predict dynamic compression accurately because they have one design flaw. When it comes to the cam, they only look at intake closing point. Here's a good example of why they do not work:

You put all the specs of your engine in the dynamic compression calculator.

You are looking at two cams.

Cam #1 is a HFT cam that has an intake closing point of 56° ABDC.

Cam #2 is a SR cam with an intake closing point of 58° ABDC.

You run the calculator and, of course, it shows the SR cam #2 has a lower dynamic compression ratio than cam #1, since the valve closes later. When, in reality, cam #2 has considerably more dynamic compression than cam #1 since it filled the cylinder with a lot more air and fuel.

The factory's use wide lobe seps because they can run more duration and still have mild manners. The bigger cams with wider lobe seps will still make good vacuum, and have better driveability than if they ground them on tight lobe seps. The factories are looking for smooth idles, and good driveability, NOT mean sounding hotrods. They also need them to pass strict emissions laws. Something that is not going to happen with 220° @ .050", ground on a 108° LSA. I understand why the OEM did what they did. I don't argue with it. I just don't think it's always the best way to go for everything.