whats the magic of a blower cam?
10-28-2009, 10:27 AM
#1
Race Director
Thread Starter
whats the magic of a blower cam?
I see some companies sell 'blower cams'. They do not publish the cam specs.
Ive heard they are a generally a smallish cam with some more exhaust duration - kind of like the hotcam (218 int., 228 exh @ .050 lift; 112 LSA, .525" lift int/exh with 1.6:1 roller rockers).
What makes these 'blower cams' so special?
Ive heard they are a generally a smallish cam with some more exhaust duration - kind of like the hotcam (218 int., 228 exh @ .050 lift; 112 LSA, .525" lift int/exh with 1.6:1 roller rockers).
What makes these 'blower cams' so special?
10-28-2009, 02:20 PM
#2
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There is nothing special about a blower cam. Pretty much any cam will work. You don't want to have too much overlap so most good blower cams are smallish with a 112 or 114 lsa. Just choose what rpm band you want your motor to operate best at. You will want to get some good valve springs with a little higher seat pressure.
10-28-2009, 04:22 PM
#3
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Here's a simulation that a forum member ran for me.
convinced me to get a blower cam
convinced me to get a blower cam
The base setup for these is the stock lt1 block.
Ported LT1 heads from above (stock valves).
1.75 headers with 26 inch pipes.
58mm throttle.
7 inch crank and 3 inch super C pulley.
First is the stock cam
Second is CC LT1 276HR-14, 220/230, .510/.510, 114
Third is CC LT1 290HR-12, 230/244, .510/.540, 112
In the real world the Comp Cam's probably have a little advance ground in but I put them in straight up for now.
Not to dramatic a difference between these two.
BTW the boost @ 6000 was 9psi = Stk cam 8.2 = 276cam 7.7 = 290cam
Your going to see the boost drop as the engine breaths better...
I'll check back in, if you want any changes & can post detailed info on your final combination ... if you want to see it.
Ported LT1 heads from above (stock valves).
1.75 headers with 26 inch pipes.
58mm throttle.
7 inch crank and 3 inch super C pulley.
First is the stock cam
Second is CC LT1 276HR-14, 220/230, .510/.510, 114
Third is CC LT1 290HR-12, 230/244, .510/.540, 112
In the real world the Comp Cam's probably have a little advance ground in but I put them in straight up for now.
Not to dramatic a difference between these two.
BTW the boost @ 6000 was 9psi = Stk cam 8.2 = 276cam 7.7 = 290cam
Your going to see the boost drop as the engine breaths better...
I'll check back in, if you want any changes & can post detailed info on your final combination ... if you want to see it.
12-30-2009, 06:27 PM
#5
Burning Brakes
Engine with turbo, s/c, or nitrous require that the exhaust be sized up to match the intake. The idea is that air is being "blown" into the engine, but exhaust is not being "sucked" out. Thus the exhuast needs more "help" or allowance to exit the engine.
For S/C, blower cams will have an increased exhuast duration or increased duration and lift. Blower cams will have at least 10 degrees more duration than a N/A exhuast lobe.
The other cam design issue is the overlap. From what I've seen, must kit/production type S/Cs are designed for torque 2-6K RPM. Thus these cams avoid increasing the overlap from a performance cam stand point.
Of course, I'm one to have a cam designed for the motor vice an of the shelf unit. Each engine is different and you'll likely find 30 Hp in the "right" cam vice a catalog entry. Key design areas are intake runners (same as N/A), intercooler (none, air, water, alcohol injection), timing (less for S/C), Head flow (same as N/A), combustion chamber design (ties into timing), compression ratio (same as N/A), etc...
For S/C, blower cams will have an increased exhuast duration or increased duration and lift. Blower cams will have at least 10 degrees more duration than a N/A exhuast lobe.
The other cam design issue is the overlap. From what I've seen, must kit/production type S/Cs are designed for torque 2-6K RPM. Thus these cams avoid increasing the overlap from a performance cam stand point.
Of course, I'm one to have a cam designed for the motor vice an of the shelf unit. Each engine is different and you'll likely find 30 Hp in the "right" cam vice a catalog entry. Key design areas are intake runners (same as N/A), intercooler (none, air, water, alcohol injection), timing (less for S/C), Head flow (same as N/A), combustion chamber design (ties into timing), compression ratio (same as N/A), etc...
