Impala SS Forum - Engine Performance

Found this on another forum and didn't see a sticky here. So not sure if this data is on here any where if so then I can delete it, if not I think its helpful.

Intro:

It seems like several people every week want to know what cam is best for their LT1 powered car or what components they need to perform a cam swap. This guide focuses on the most common and proven camshafts available for LT1’s as well as the most common and proven valve train components. The majority of focus is on LT1 cars running stock bottom ends and stock heads however it still will offer some insight to those who have built bottom ends and head work. I encourage you to read the entire guide and hopefully you may learn something and allow yourself to select the perfect cam and valve train components for your particular setup.

Part 1: Choosing A Camshaft:

-Bigger is NOT always better.
-Sound does NOT equal power.
-Before selecting a cam you must develop your needs/wants/plans for your car, as that is what should determine which camshaft you select.

Ex: Stock 1996 B-Body Camshaft Specs: 191/196 0.418/0.430 lift 111 LSA

Duration: Duration is the time that the valve is open. Increasing the duration keeps the valves open longer which increases top-end power therefore raising the power band.
Lift: Lift is the maximum amount in inches that the valves are open. Increasing lift equals more horsepower and torque but at the same time can lead to more peaky torque curves.
Lobe Separation: Lobes Separation Angle (LSA) is the number of degrees the intake and exhaust lobes are separated. The lower the LSA is, the more overlap you have ,if the cam duration and lobe profiles remain the same.

OVERLAP:This is the killer for street engines. Overlap is the amount of degrees that the intake and exhaust valves are open at the same time. Unburned air/fuel mixture will be pushed through the cylinder when both valves are open and straight out the exhaust. This decreases mileage, increases emissions, and make the engine run rough at low rpms. It also decreases low-rpm torque, and hurts throttle response.
All cams have some amount of overlap. Stock cams all try to keep the overlap low for the above reasons.
More duration with no other changes will increase overlap. One way of lowering overlap after it's been increased by more duration is to increase lobe separation. This is because moving the lobes away from each other decreases the time they are open simultaneously.

-If you are in the market for a camshaft purely for sound and are willing to sacrifice usable power and drivability then something along the lines of the cc306 or GM847 will suite you well. However, if you want the full potential out of these cams you will need to be shifting at 6400+ rpm which is VERY risky on the stock bottom end. Some have been lucky while others have not but a stock block typically will not last long if being shifted at or above 6400/6500rpm. Just because camshafts as large as the cc306, GM847, etc. make more peak power, doesn't mean the car is faster. The key is usable power which is the power under the curve and you want a cam that fits in the usable power range that YOU want. Camshafts that large, lack low-end power because their power bands are more geared towards higher rpm's. Also, the worst thing you can do is run a cam of any sorts and not rev it to where it wants to be. Not revving a car out to where it wants to be will result in poor track times for your setup. An example below…

(Ex: I once ran the cc503 in my LT1 and shifted it at the stock shift point which is lower than desired for that particular cam. When I bumped the shifts up to where they wanted to be (6300ish) I picked up .4 and 4 mph in the quarter mile. If say I wasn’t willing to rev past 6000rpm, that cc503 would be hindering me. In that case I would be better off running a much smaller cam like the LPE 211/219 or something along those lines.)

***Now...I do not want you to think that the Comp 230/236, cc306, or GM847 etc. etc. are bad camshafts because they are not. Those cams have been proven for years to make great power and perform great at the track. Because of their large durations I like to use them as examples to prove points well. For some they may be the perfect camshaft choice but for most there tends to be better alternatives with a stock block/headed LT1, just depends what YOU want from the car. If you’re willing to rev the car out to where it’s deemed rather unsafe on the stock bottom end and your primary goal is to run the fastest ET’s possible then by all means they would be excellent choices. Unfortunately stock LT1 heads do not let these cams to be used to their full potential. Those with built bottom ends and head work greatly benefit from the use of these cams.***

-If you error on choosing a cam too small, you will still enjoy driving the car more than you did while it was stock and will be motivated to go a little bigger next time around. If you error on choosing a cam too large, it will more than likely hurt your enjoyment of driving the car compared to stock so the proper camshaft selection is very important.

-Below are some of the most popular and proven off the-shelf camshafts that will work great with LTx’s while performing well on the street and on the track. Also listed is the option to go the Custom Grind route. With today’s technology and the expertise and knowledge of certain individuals/companies, going with a custom grind is many times the best overall option.

***Keep in mind, the advertised rpm range of a particular cam given by the manufacturer is not necessarily 100% accurate and most cases it is not! Remember that the next time your looking through a catalog or on a website at a cam that you like.***

Custom Grind:

Pros: The optimal choice for the most power and best drivability because the camshaft is ground specifically for your setup and what you want out of the car.
Cons: Cost a little more than an off the-shelf camshaft (another $50-100 or so). If you change your setup down the road, the custom cam may not work to its potential on your new setup.
Pass Emissions?: Yes or No it’s up to you.
Shift Point for Maximum Performance: Wherever you are willing to rev it to.
Idle Characteristics: Whatever your looking for, from sleeper to choppy.
M6; Require Gears?: On a manual car, gearing plays a big part in cam size.
A4; Require Stall?: On an auto car, more stall is needed for larger cams but a custom camshaft can be designed around your existing or planned stall size.
Where can I get a Custom Grind?: A few places offer custom grinds with the most popular in the LTx crowd being Lloyd Elliott and Advanced Induction. Other good choices are Ed Curtis and Cam Motions.

Comp Cams:

cc502: (218/224 .528/.537 112lsa) w/ 1.6RR's
Features Comp's relatively newer technology XE (Xtreme Energy) lobes for more top-end power. Exhibits great drivability with a strong mid-range and moderately good top-end. Similar to the LT4 “Hot Cam” in performance and drivability.
Pass Emissions?: Yes
Shift Point for Maximum Performance: 6100-6200rpm
Idle Characteristics: Moderately Choppy Idle
M6; Require Gears?: No
A4; Require Stall?: 2500+ Stall Speed

XFI 466: (218/224 .570/.565 113lsa) w/ 1.6RR's
A newer grind from Comp Cams. It utilizes their very aggressive XFI (Xtreme Fuel Injection) lobes that are good for increased power over older technology lobes like Magnum etc. Along with excellent drivability it exhibits a very strong mid-range with a good low-end and moderately strong top-end. Essentially a beefed up LT4 “Hot Cam” and cc502. With its 113lsa it takes a more trained ear to know that it’s there making it a decent “sleeper” cam. Note: Due to its very aggressive lobe design, requires the use of “Beehive” valve springs.
Pass Emissions?: Yes
[b]Shift Point for Maximum Performance:[b] 6100-6200rpm
Idle Characteristics: Smooth Idle
M6; Require Gears?: No
A4; Require Stall?: 2500+ Stall Speed

cc305: (220/230 .544/.544 114lsa) w/ 1.6RR's
Features Comp’s Magnum lobes with are older technology but proven not to take a beating on valve train components. Comes in a 112lsa and 114lsa. The 112lsa will have slightly more top-end power over the 114lsa which will have slightly more low-end power. The 114lsa is sometimes favored by cars running Nitrous or Blowers because it provides less overlap than the 112lsa. The less overlap leads to more potential power from the Nitrous/Blower. In the case of Nitrous your typical 75-150 shot will not really benefit from the 114lsa over the 112lsa, different when the shot increases beyond that however. Pretty comparable to the LT4 “Hot Cam” in terms of power with the cc503/GM846 a step ahead.
Pass Emissions?: Yes
Shift Point for Maximum Performance: 6200-6300rpm
Idle Characteristics: 114lsa will have a Smooth Idle, 112lsa will have a more Choppy Idle
M6; Require Gears?: No
A4; Require Stall?: 2500+ Stall Speed