I am looking into a new cam. For now im not changing the heads. I may swich to a carb though, the car will be track only so i'm concerned with WOT performance only....I'm in need of opinions; I really don't know much about cams, but I do want one that will be swapable to a larger (350/383) motor...So what it boils down to is, What specs should I look for when I but the cam? Also, am I correct in thinking any performance cam will require tuning the computer? I don't really want to get into tuning, one of the reasons I may go to a carb...Thanks

 

You have TBI heads, the car will be track only, and you don't plan on changing them? Something doesn't add up.

First thing, the TBI heads are of such extremely low performance value, I'm not even going to comment. They have little "ramps" in the intake ports that swirl the intake charge. This is good for low end torque, but above 3500 rom or so, I would call them a flow impediment, at best.

Secondly, stock castings max out at about .460-.480" lift at the valve (actual tolerances vary, so checking is suggested). This limits the amount of lift you can run. That, in turn, limits the cam selection as, generally, lift and duration go hand in hand. As you increase the general lobe lift, you increase the duration, which increases its "high performance" aspect. At least, moreso over a "torquer-type" grind. Look at some aftermarket cams. Specifically, the ones with the RPM range that is about 2000-6000 or so RPM. Look at the lift then. Hovers right about .500, more or less, dependin gon company, as each has their own lobe profiles. Considering as how factory castings limit the lift to sub-.480", that doesn't work too well.

So, now that your cam selection is limited, consider for a moment, if you will, head flow versus cam selection. Remember those swirl ports and how they aren't the best for air flow? The higher RPM's that are typical of the more "strip" cams require a bit more air up there. The valves are opening and closing faster, so there is less time for the air and fuel to get sucked into the chamber, thus, the ports must flow more.

Third point, the swap over capability. You have a 305 now. Any listed cam is based, usually, on a 350-based platform, add about 200 RPM's or so to the RPM range to get your range. So, in essence, any listed cam will be a tad hotter than what they say. Just another thing to keep in mind. Now, if you do go to a 383, subtract about 200 or so RPM's from the advertised range, or about 400 from the running range in the 305. That means that any cam you select as a "hotter" cam for your engine, will be a bit tamer in the 383.

Another point to consider, torque converter. For any true strip cam, I would suggest at least a 3000 RPM stall. When you toss an aftermarkey cam in, you move the peak torque point up in the RPM range. You need that higher stall so you don't bog off the line, which is bad, espectially considering your intents are strip-only.

Yet another point, compression. Strip cams like higher compression. As you increase the duration on a given lobe seperation angle, you increase the amount of cylinder pressure that gets bled off with the valve timing. Lower cylinder pressures mean less torque. That means dogginess which is bad. TBI's aren't known for the stellar compression ratios, either.

Another point, rear gears. Again, as you increase the cam (and heads), you move the powerband and peak torque up. That needs a little bit more gearing to get you off the line. Not sure what yours is, but just another thing to consider. A popular street/strip gear is the 3.73. That compliments pretty much most cams that can do double duty. If you really want to get series, ratios like 4.11 and up are available.

So, in the end, everything is going to boil down the the heads. For an L03, on a nearly stock tune, I would take a peek at the LT1 cam.

 

Thanks for the legnthy reply Steakman, what I ment to say was, I won't be changing the heads at the tome of cam swap...I'm on the hunt for an lt1 cam.


And I am planning on the 4.11/posi as I have the ever so lame 2.73/pegleg now.

Just read Shifty's Lt1 cam digest, that cleared up alot of q's of mine...