Introduction
With so many LS3 and L92 engines on the road and new Camaros already starting to be modified, it was high time GMHTP took a crack at testing a gaggle of streetable cams perfect for the new Gen IV mill. But of course, then began the debate over what exactly defines "streetability"- one man's idea of wild being another's idea of "almost enough." So the idea of driveability and street manners are wildly subjective. Even power and torque, being quantifiable numbers, can be subjective as to how much is enough (if there is such a thing) or where in the operating range you need it. So the question becomes: how do you quantify (objectively) how streetable a cam is? Well, we think we have the answer. Follow along as we test out some of the best LS3 street cams on the market for not just horsepower and torque, but also how well the cam matches up to your subjective scale of driveability.
Criteria
We contacted a large handful of the tuners and manufacturers specializing in LS performance and requested an LS3 cam with street manners for testing. Knowing that it is subjective, we had to put some caps on things to keep it from getting too wild. As such, the cam specs that all suppliers were required to adhere to were:
1. The cam CANNOT require valve reliefs to be cut into the pistons!
2. Minimum 112-degree LSA
3. Maximum 0.650-inch lift
4. Must idle at 950 rpm or preferably less
5. Must have less than 50 kPa manifold absolute pressure at 950 rpm idle point
6. Must keep stock pushrod length and production hydraulic lifters
7. Valvespring replacement is OK
8. All cams will be measured and specs reported in the article
While we tested the power of these cams we also added a vacuum, or manifold absolute pressure (MAP), component to our evaluation. This is a good indicator (amongst many other factors) of how the engine would act on the street.
MAP at Idle & Low Speed
To evaluate the possible street manners of our group of cams we are as concerned about how likely it will operate in the car as to much as power and torque it will produce. For those not wanting to adjust their driving style to gain performance, we are calculating whether the cam will cause poor idle, surging at low speed, and stumbles coming to a stop. Some can tolerate that-and the power numbers here won't impress you-but hopefully you still gain insight into how to make that wild cam a little more liveable. We decided to test the vacuum at idle [at 950 rpm]. This idle is a little high for a "streetable" cam, but when running on the dyno we determined this would be an idle at which we could easily measure MAP (manifold absolute pressure). In analyzing the data after the testing, we found we inadvertently recorded MAP values for the 1,500-1,600 rpm range, so we used that data point as well.
From experience, cams that fit a large segment of the market's definition of street manners run 35-50 kPa and idle from 750-850 rpm. More aggressive cams-the ones where a smaller segment of the market would classify it as streetable-can be up to 65-70+ kPa at idle and must idle up over 900 rpm. When getting into a 80 kPa range the car has a noticeable rock at idle and likely experiences surge when driving at low speed, low throttle situations (1,400-1,700 rpm, low throttle input). Some people still classify this as streetable, but for the purpose of this article, when you are giving up "manners" or have to adjust your driving style to avoid these situations, it doesn't fit our definition of streetable.