Road Racing Vs. Drag Racing Cam Profiles
12-14-2005, 08:56 AM
#101
ZO6er
We use the comp cams 26921 spring kit with our GT-11 cam in packages that we warranty for 2 yrs/24K miles, and don't have any issues with springs wearing out. To be honest, I am not aware of a single spring failure with this setup, but if you're going to be road racing with it, it would be a good idea to check spring tension periodically, and replace them at the first sign of losing pressure. A road race vehicle will be subjected to much higher stress on the valvesprings than a car that is street driven would be.
As for the lobes, our cams are ground on a standard symmetrical lobe, not the fast ramp rate lobes.
Hope this helps,
Ed
We use the comp cams 26921 spring kit with our GT-11 cam in packages that we warranty for 2 yrs/24K miles, and don't have any issues with springs wearing out. To be honest, I am not aware of a single spring failure with this setup, but if you're going to be road racing with it, it would be a good idea to check spring tension periodically, and replace them at the first sign of losing pressure. A road race vehicle will be subjected to much higher stress on the valvesprings than a car that is street driven would be.
As for the lobes, our cams are ground on a standard symmetrical lobe, not the fast ramp rate lobes.
Hope this helps,
Ed
12-14-2005, 11:47 AM
#102
How did I miss this thread? While the discussion is about cams, maybe it should backup up to the underlying objectives.
If you are racing in a competitive class with rules, you need the cam that stretches the limit of the rules. Other competitors and the engine builders they use would know the best setup from the rules. My engine builder draws on the results of maybe 50 or racers in similar cars on similar tracks.
For example, Our oval track car, which uses 4500-7100 or so uses a 248/256 107/+4 with 1.8 intake rocker. It is a solid lifter flat tappet cam, and the ramp (159deg@.200 lift) is just about as violent as you can get with its limiting factors, .842” diameter flat tappet solid lifters, steel valves, and non-shaft rockers. Note that this setup eats 2 or 3 sets of valve springs a year and gets a new set of valves at an annual rebuild.
In competitive racing, a 2-3 feet at the end of a straight can be difference between making or blocking a pass for position.
If it is for an open track day, the two most important things are reliability and drivability. There are never enough track days, and they are expensive (travel, lodging, fees, tires, etc.). You need to maximize track time. You probably also want to maximize track time. So the cam should be something that will cause no maintenance issues.
The important part of going fast is coming out of the corners fast. This is a balancing act, with more power than traction. In a drag race, you spin the tires. In a road race, you spin the car, in front of other cars, into guardrails and other solid objects, into dirt that catches a wheel making the car an airplane (or beachball). So you need a setup that will be smooth and progressive over a wide range of throttle openings over a broad rev range.
After that, tires brakes, shocks, and suspension tuning is where I believe most other Z06 drivers will point you. The gain (in lap time or straightway speed) between 400 and 500 hp is probably smaller than from a fresh set of Hoosiers.
If you are racing in a competitive class with rules, you need the cam that stretches the limit of the rules. Other competitors and the engine builders they use would know the best setup from the rules. My engine builder draws on the results of maybe 50 or racers in similar cars on similar tracks.
For example, Our oval track car, which uses 4500-7100 or so uses a 248/256 107/+4 with 1.8 intake rocker. It is a solid lifter flat tappet cam, and the ramp (159deg@.200 lift) is just about as violent as you can get with its limiting factors, .842” diameter flat tappet solid lifters, steel valves, and non-shaft rockers. Note that this setup eats 2 or 3 sets of valve springs a year and gets a new set of valves at an annual rebuild.
In competitive racing, a 2-3 feet at the end of a straight can be difference between making or blocking a pass for position.
If it is for an open track day, the two most important things are reliability and drivability. There are never enough track days, and they are expensive (travel, lodging, fees, tires, etc.). You need to maximize track time. You probably also want to maximize track time. So the cam should be something that will cause no maintenance issues.
The important part of going fast is coming out of the corners fast. This is a balancing act, with more power than traction. In a drag race, you spin the tires. In a road race, you spin the car, in front of other cars, into guardrails and other solid objects, into dirt that catches a wheel making the car an airplane (or beachball). So you need a setup that will be smooth and progressive over a wide range of throttle openings over a broad rev range.
After that, tires brakes, shocks, and suspension tuning is where I believe most other Z06 drivers will point you. The gain (in lap time or straightway speed) between 400 and 500 hp is probably smaller than from a fresh set of Hoosiers.
12-14-2005, 11:57 AM
#103
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Originally Posted by DavidNJ
How did I miss this thread? While the discussion is about cams, maybe it should backup up to the underlying objectives.
If you are racing in a competitive class with rules, you need the cam that stretches the limit of the rules. Other competitors and the engine builders they use would know the best setup from the rules. My engine builder draws on the results of maybe 50 or racers in similar cars on similar tracks.
For example, Our oval track car, which uses 4500-7100 or so uses a 248/256 107/+4 with 1.8 intake rocker. It is a solid lifter flat tappet cam, and the ramp (159deg@.200 lift) is just about as violent as you can get with its limiting factors, .842” diameter flat tappet solid lifters, steel valves, and non-shaft rockers. Note that this setup eats 2 or 3 sets of valve springs a year and gets a new set of valves at an annual rebuild.
In competitive racing, a 2-3 feet at the end of a straight can be difference between making or blocking a pass for position.
If it is for an open track day, the two most important things are reliability and drivability. There are never enough track days, and they are expensive (travel, lodging, fees, tires, etc.). You need to maximize track time. You probably also want to maximize track time. So the cam should be something that will cause no maintenance issues.
The important part of going fast is coming out of the corners fast. This is a balancing act, with more power than traction. In a drag race, you spin the tires. In a road race, you spin the car, in front of other cars, into guardrails and other solid objects, into dirt that catches a wheel making the car an airplane (or beachball). So you need a setup that will be smooth and progressive over a wide range of throttle openings over a broad rev range.
After that, tires brakes, shocks, and suspension tuning is where I believe most other Z06 drivers will point you. The gain (in lap time or straightway speed) between 400 and 500 hp is probably smaller than from a fresh set of Hoosiers.
If you are racing in a competitive class with rules, you need the cam that stretches the limit of the rules. Other competitors and the engine builders they use would know the best setup from the rules. My engine builder draws on the results of maybe 50 or racers in similar cars on similar tracks.
For example, Our oval track car, which uses 4500-7100 or so uses a 248/256 107/+4 with 1.8 intake rocker. It is a solid lifter flat tappet cam, and the ramp (159deg@.200 lift) is just about as violent as you can get with its limiting factors, .842” diameter flat tappet solid lifters, steel valves, and non-shaft rockers. Note that this setup eats 2 or 3 sets of valve springs a year and gets a new set of valves at an annual rebuild.
In competitive racing, a 2-3 feet at the end of a straight can be difference between making or blocking a pass for position.
If it is for an open track day, the two most important things are reliability and drivability. There are never enough track days, and they are expensive (travel, lodging, fees, tires, etc.). You need to maximize track time. You probably also want to maximize track time. So the cam should be something that will cause no maintenance issues.
The important part of going fast is coming out of the corners fast. This is a balancing act, with more power than traction. In a drag race, you spin the tires. In a road race, you spin the car, in front of other cars, into guardrails and other solid objects, into dirt that catches a wheel making the car an airplane (or beachball). So you need a setup that will be smooth and progressive over a wide range of throttle openings over a broad rev range.
After that, tires brakes, shocks, and suspension tuning is where I believe most other Z06 drivers will point you. The gain (in lap time or straightway speed) between 400 and 500 hp is probably smaller than from a fresh set of Hoosiers.
12-14-2005, 09:17 PM
#104
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DavidNJ
You are absolutely right.
The assumption for this thread is the car is set up with the correct stuff, brakes, brake bias, ride height, correct spring rate, right alignment specs, appropriate shock rebound, correct tire grip for the surface, corner balanced, etc...
The car is used for open track day.
You are absolutely right.
The assumption for this thread is the car is set up with the correct stuff, brakes, brake bias, ride height, correct spring rate, right alignment specs, appropriate shock rebound, correct tire grip for the surface, corner balanced, etc...
The car is used for open track day.
12-17-2005, 10:14 PM
#105
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I run a big cam and it works fine. The car is 450/400 346 CI and three years old with over 5500 track miles Power peaks at 6500 and redline is 6700. You can have a big cam and run nicely. I have LS6 heads ported and stock TB with LG headers. You need brakes and suspension before you bother with HP 
12-18-2005, 12:02 AM
#107
LG sells cams for this setup. Has lots of road racing experience. And charges the same as others selling Comp Cams. Unfortunately, he doesn't tell you the cam specs. However you can get that from the cam after you get it, with a degree wheel and a dial indicator. And you will need those for the installation anyway.
My guess is he will recommend something between 224 and and 236 with even intake and exhausts or with the exhaust 4 deg bigger.
That setup will probably be choked for air above 6000. Most of the AFR posts seemed to include the FAST 90 intake and a 90mm TB.
I would probably leave the stock cam alone and spend the money on more track time (I like renting the track for practice), and fresh tires. Fresh tires always make you feel like Michael Schumacker, Tony Stewart, etc. Especially when everyone else is on worn tires.
My guess is he will recommend something between 224 and and 236 with even intake and exhausts or with the exhaust 4 deg bigger.
That setup will probably be choked for air above 6000. Most of the AFR posts seemed to include the FAST 90 intake and a 90mm TB.
I would probably leave the stock cam alone and spend the money on more track time (I like renting the track for practice), and fresh tires. Fresh tires always make you feel like Michael Schumacker, Tony Stewart, etc. Especially when everyone else is on worn tires.
