Yeah, but we'll probably never catch up to the number of pages for Hottie of the Day. ...and never make it to "sticky" status.

 

The nicest thing about this thread is that since we're talking about technical stuff that requires some intelligent thinking, you don't have to worry about some ignorant arguement being started from the village idiot, just for the sake of an arguement.
Sorry I probably jinxed this thread now.[:@]

 

hehe, just had to get my little funny comment in.

 

Here's a HOWTO on checking valve to piston clearance:

http://www.advanceautoparts.com/engl...p#Measurements


...and this one on Thumper Talk:

http://www.thumpertalk.com/forum/sho...d.php?t=589348

 

I think that cam would be a gret choice, and honestly, the numbers are so close, I'm not sure you would notice any difference in the two.
If there was a difference, based on the numbers, it would be more power overall (lift), and a little stronger lowend power.

This is something I did for the forum I regularly frequent.
Is this the kind of info you're looking for?

Here is a short explanation of some of the terms, and what they mean.

Duration
This is the amount of time, in crankshaft degrees that the valve is open. Most often, duration is expressed as an 'advertised' number, which, for the purposes of comparing one cam to another, is almost completely useless.

Duration at .050"
This is a known constant way of measuring duration. Unfortunately, too many manufacturers, or retailers don't use it. The valve event is measured from .050" lift, on the opening ramp, to .050" lift on the closing ramp of the cam lobe. If all cams are measured in this way, then you can directly compare one to another.

Lift
Pretty simple. The amount that the valve is open, either in inches, or mm.

Lobe separation
The distance between the intake, and exhaust centerline in cam degrees.

What does a performance cam do for me?

Duration.
Generally speaking, the duration will determine the useful RPM range of your engine. As duration is increased, the power band moves up in the RPM range. What you gain on one end, you will lose on the other.

Lift
Increasing the lift will almost always result in increased torque, and horsepower. It has been said that lift = torque, and horsepower.

Lobe separation.
Decreasing the lobe separation (moving the lobes closer to each other) will benefit low,and lower midrange torque and horsepower, but create a rougher idle, and peakier torque curve. Increasing the lobe centerline will reduce overlap, broaden the torque curve, provide a smoother idle, and better top end power.


Some things to consider.
Because of the large valve area, the 4 valve/cylinder motors are much more duration sensitive than the 2 valve/cylinder motors.In other words,the same cam will net very different results on the two motors. The 4 valve motors produce more power with less duration, and overlap, but will also start to lose low RPM power in a real hurry as duration at .050" increases beyond 210-220 degrees.

A little FYI on the grind/regrind process.

Many people think you just take a little off the bottom (base circle), to get more lift, or you can tell the grinder what numbers you want, and he will custom grind it.

This is how it really works.

The cam grinding machine is a kind of copy machine.
If you have ever seen a copy lathe in a wood shop, for making spindles, its very similar.
When you grind a cam, you need to use a master template. This template has the lobe shape, which determines the lift, and duration.
During grinding, the entire lobe is ground, and the new shape takes on the charachteristics of master template.

How do you increase lift?
Take more off the bottom than you do off the top.
The lift is determined by the total lobe lobe height, minus the base circle diameter.
Its an exageration, but if you leave the tip of the lobe, but take material off the bottom, and sides(reduce the base circle diameter), then the lift is increased, as is , obviously the duration.
The lifter rests in a different place, but will open further.
How cam the lifter just re-adjust?
Hydraulic preload.
The GTi has substantial lifter preload, and there is alot of room for base circle reduction, and increased lift, or in other words, a completely reworked lobe shape.

If you still cannot grasp the concept, picture the lobe to be a rectangle, taller than it is wide.
Place a triangle inside the rectangle.
This is how the lobe will be re-profiled.
Grab a vernier caliper and measure the width of the lobe (to reflect the base circle diameter-this will be the smallest lobe number).
For the GT, it will be about 33mm
Now measure the total height.
This should be about 40.5mm
Subtract the 33 from the 40.5.
This is your lift.
Imagine taking material off the sides and bottom only.

 

Well, goingby what Zombie W. wrote, the 293 grind has the highest lift, closest lift center spacing and second shortest duration, which all point to giving you more on the low-end.

Beyond what Zombie listed, I'm not quite sure what you are looking for....although I'm pretty sure you've already figured the whole thing out as well or better than the rest of us.

Thanks for posting the graphs. That info, combined with Zombie's explanation, was very educational to me. I love it when a forum works as it should

 

Mooredan and Zomby Woof,

Just wanted to say thanks for generating some decent conversation and providing solid information. Too many times things on forums get into debating colors and handgrips. Very nice to see some high end info being swapped in this thread. Thanks guys.