I'm still having trouble understanding the exact details of how cams work, and what all the numbers mean. I've read plenty of articles about what they do and how they work, but a lot of the stuff I can't comprehend no matter how many times I read it.

That said, I see a lot of people recommending Comp Cams' Xtreme Energy 262 cam for mild 305 buildups and also noticed that CarCraft used the same cam in their 325HP 305 buildup article. Comp Cams says the recommended usage for this particular cam is for 305/350s with a better chip and upgraded exhaust.

However, there is another cam that I haven't seen anyone recommend which is the 268 cam. It's recommended usage is for 350s with upgraded chip/exhaust, injectors, plenum, and runners.

On the assumption that an similarly built carbureted setup (such as better intake, better rods/hangar, upgraded exhaust)could work almost, if not equally as well as the aforementioned 350 TPI, why aren't more people using this cam for their buildups? Does it cause some sort of fuel economy problems? Not enough vacuum? A decrease in power as opposed to increase?

I am just wondering because I am beginning to look at my options for cams and noticed that a lot of people have recommended the 262 for 305 buildups, even though the 268 looks like a better choice according to Comp's recommendations. I know every setup is different, however, which is why I am looking for some solid facts on why I should or should not consider this cam for my engine.

 

People are using it.

The 12-268-4 version is the computer-compatible one, 12-242-2 the none computer one.

It's a bit too much cam for the typical TPI setup. Some stock heads have lift clearance issues.

 

Plus it's much better to "under-cam" and engine than to "over-cam" it.

Too small of a cam usually gives (as you mentioned) better vacuum at idle, more grunt off idle, and easier to tune for. About the only down side is less upper RPM HP.

Too big of a cam usually does just the opposite. It should be easy to figure out which would be easier to deal with.

This is taking for granted that "bigger" means longer duration, more lift, and more overlap.

There are ways to get a "bigger" cam to behave like a smaller cam does. One is to grind it with a wider Lobe Seperation Angle (LSA) to reduce overlap. Another is to play with the Intake Centerline (IC) until the torque curve matches the application.

But in reality, doing this stuff to compensate for a cam that's too big could easily be avoided if the right cam is used in the first place.

 

When should I start determining what cam to choose?

I have a goal of reaching a 13-second quarter mile with this 305 that I have in the car. I have Hooker 2055 headers, a 3" Catco 9118 cat, and a Hooker 3" catback waiting to be installed, as well as a ZZ4 intake. Later on, I want to put some better heads on the engine (perhaps some World 305 heads with a port & polish job done by me) and better gears (I'm thinking 3.73s, but this is a daily driver).

I do want good driveability, but I want the most power I can get out of the cam that I choose. Sound is not really a factor.

 

The main difference between those two cams (from the specs) is the LSA, with the non computer one having 110, and the computer type 114. Although they list the same RPM range for both, the computer type will have a better low end and weaker top end.

Are you sticking with a computer or not?

You didn't mention torque converter, vital part of the "package". One that stalls at about 3000 RPMs will put either cam well into the power band off the line, which is key to low ETs.

You're basically building what I had, it sounds like.

 

Yes, I am keeping the computer.