I have an 03 Z06 that is bone stock. I was looking into getting a cam and wanted to know what everyones opinion on doing so was. What kind of numbers could I expect? I told the guys at Vengeance that I wanted a stock reliability, lopey and torquey cam. I don't want to give up low end grunt for top end power. They said they could come up with a custom grind cam that would suit that. I was just looking for some feedback. I did do a search on this before I posted and didn't find too much. Also, what would it do to the gas mileage?

 

You are in good shape if you like lope. The trickiest scenario is one in which the driver wants low end power with a good peak, but wants no lope, and a very stock-like idle. Basically, the better performing cams (both in peak and lower end) have more overlap than those dubbed "stealth cams", which have a more stock-like idle. I wanted a sleeper car, but every time I looked at dyno curves, I soon learned that you give up low or high-end power with that type of a cam.

The reason is, to get a stock-ish idle, you have to keep the overlap above a certain point. What point that is depends on how stock-like you want it. Let's say you want a mild idle, and would accept a little more chop than stock, but don't want a real lope. You'd probably want to stay with less than -5 degrees of overlap. Ok, so how do you keep your overlap under -5 with a given cam, such as a 220/220? One of two ways. Either 1. widen your LSA, or 2. keep the LSA lower and drop your durations to the point that your overlap hits your range. In this case, say it's a 224/224 on a 112LSA. You can drop the LSA to 115 to hit a -6 degree overlap, or you can narrow your duration to 218 to hit the same overlap, and thus same idle quality.

If you opt for #1, you tend to hurt your low-end power. Look at dyno graphs for two different cars that have identical cams with different LSA's. There are tons of guys with the TR224 on a 112 and with the same am on a 114. The ones on a 114 don't have as good of a low end, and the peak isn't quite as strong... The low-end portion has to do with Dynamic Compression Ratio, because of the later intake closing on a wider LSA.

If you opt for #2, and narrow the duration so that your overlap hits your target area, you'll keep the low end beefier, because your LSA will be lower like you want, but because your durations are smaller, you won't move as much air through your engine, and thus you won't push as much peak power.

That said, if you have an LS6 and are going cam-only with longtubes, you should be able to get 400 to the wheel without going too large. My 224/224 .581/.581 on a 112LSA has some lope to it, and it idles pretty darned well, and I'm pushing 410 at the wheel through ported 5.3L heads. I imagine going through stock LS6 heads, I'd give up 10 or 15 whp. You could go a bit bigger than mine and still have a good idle, and get into the lower 400's. A 228/232 on a 115 like the G5X1E would idle well, and probably make 10 more hp than the 224, but it wouldn't be quite as stout at 2,500rpm. It would tend to come up in the higher range, but still well within the range you'd be in under a full-throttle romp through the gears.

If you aren't planning on doing long-tubes, then you are going to have to keep your overlap below -5 or so, because the stock exhaust manifolds are too restrictive to get much more overlap. This is well documented over on LS1tech.com. With something like the Cheatr cam through stock manifolds, you'd probably put down 380-385whp or so, but below 3,500rpm's, you won't be pushing out any more torque, so your car won't feel any faster until you get the rpm's up (just go look at anyone's before/after dyno curve for that cam).

As far as gas mileage, unless you go huge, you shouldn't have a problem. My mileage has only changed because I push that right peddle more now... When I take it easy, my mileage is comparable to what it was before.

 

This whole NA thing is new to me. I am coming from an 03 cobra and all we talked about was more boost. What aspect of the cam produces the loping generally associated with cams? Would long tubes be better instead?

 

Long tubes will enhance the cam, but the best bang for the buck is a cam. We're doing one right now on a friend's car.

 

GREAT POST! You've done a terrific job of capturing some of the arcana and making it at least more understandable. Thanks - this is why I go browsing the posts, even if I'm not looking for anything in particular. Something like this LSA discussion jumps out and makes sense of something otherwise not well understood.

Have a great weekend!

 

The big factor in loping is overlap. The more overlap, the more lope; the less overlap, the less lope. You calculate overlap by adding your durations, dividing by 4, then subtracting the LSA from that number, and then multiplying by 2. For example, 224/224 on a 112 is 224 + 224 = 448 / 4 = 112 - 112 = 0 x 2 = 0 overlap. 0 degree overlap is quasi lopey. Here's my idle video to give you an idea of what 0 sounds like. You can go and find some sound clips of bigger cams with more overlap, and smaller ones with less to get a feel for how much overlap change affects lope. Oh, and the louder your catback is, the more noticeable any lope will be. My cam through longtubes with no cats and a loud catback sounds much more obnoxious than my car through a Z06 Ti.

 

Hey, thanks man. I spent a few months really researching the crap out of this stuff. I'm still by no means an expert, but I think I'm a well-educated layman. I think anyone considering going with a cam should really learn the basics before making a decision. It's such a personal choice that I hate to see people just take a poll and get whatever the people wandering in to that post advocate. It gets really bad over on LS1tech.com, too, with everybody advocating HUGE cams. Have a good weekend too, buddy...