Blower Cams
01-02-2005, 07:09 PM
#12
Originally Posted by SportSide 5.3
Remember this. The lobe seperation angle is "A" key in idle quality. Take this camshaft.
210/210 @ .05, Comp Lobe. With a lobe seperation angle of 115*, it has -20* of valve overlap @ .05 valve lift. Tightening the lobe distance to 110* creates more overlap... -10*. Take a look at that chart. It helps. Move the seperation closer, and you see how the lobes overlap. Move the seperation apart and you have less overlap.
So for example, a 220/220 on a 115lsa, may have the exact same idle characteristics of a 210/210 on a 110lsa.
Simply put: Overlap = duration vs. lobe distance (lsa)
210/210 @ .05, Comp Lobe. With a lobe seperation angle of 115*, it has -20* of valve overlap @ .05 valve lift. Tightening the lobe distance to 110* creates more overlap... -10*. Take a look at that chart. It helps. Move the seperation closer, and you see how the lobes overlap. Move the seperation apart and you have less overlap.
So for example, a 220/220 on a 115lsa, may have the exact same idle characteristics of a 210/210 on a 110lsa.
Simply put: Overlap = duration vs. lobe distance (lsa)
whats the calculation for overlap?
01-02-2005, 07:10 PM
#13
Originally Posted by Flyer
Personally ... I still don't like the huge split going on there knowing your gonna be putting headers on there. I would go with the 218/224 without a question or second thought. The only 2nd thought I might have would be going to something a little bigger.
There will be plenty of power under the curve with the blower on top.
There will be plenty of power under the curve with the blower on top.
the second is Vinci's 045,
"THE TRUCKER"
STREET / STRIP / POWER
RPM RANGE 2200 TO 6000
TUNING REQUIRED
POWERFUL CHOPPY IDLE
DYNAMITE WITH A WHEEZEr.
01-02-2005, 07:14 PM
#14
This is my 3rd serious contender:
Thunder Racing Custom "Old Man Truck" Camshaft - 214/220 .600/.525 115+2 LSA This is the perfect cam for someone looking for a stock range power band and stock sounding idle. Significant horsepower gains throughout the RPM range. No computer tuning required.
Thunder Racing Custom "Old Man Truck" Camshaft - 214/220 .600/.525 115+2 LSA This is the perfect cam for someone looking for a stock range power band and stock sounding idle. Significant horsepower gains throughout the RPM range. No computer tuning required.
01-02-2005, 07:16 PM
#15
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Nope you had it, I just wanted to clear it up that overlap is the main cause of the bad idle quality, and not lsa.
Some think that a camshaft must have a 115* lsa to idle well. This is not the case. Sorry if I was soap boxing.
You can use (Intake Duration + Exhaust Duration) / 2 - (LSA * 2).
Ex.
210/210 on a 110lsa
210 + 210 / 2 = (210-) 110 * 2 = (220) = -10* of overlap @ .05
Some think that a camshaft must have a 115* lsa to idle well. This is not the case. Sorry if I was soap boxing.
You can use (Intake Duration + Exhaust Duration) / 2 - (LSA * 2).
Ex.
210/210 on a 110lsa
210 + 210 / 2 = (210-) 110 * 2 = (220) = -10* of overlap @ .05
01-02-2005, 07:20 PM
#16
Originally Posted by SportSide 5.3
Nope you had it, I just wanted to clear it up that overlap is the main cause of the bad idle quality, and not lsa.
Some think that a camshaft must have a 115* lsa to idle well. This is not the case. Sorry if I was soap boxing.
Some think that a camshaft must have a 115* lsa to idle well. This is not the case. Sorry if I was soap boxing.
01-02-2005, 07:25 PM
#17
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A wide lobe seperation is a sacrifice of power for a decent idle quality. Even with a blower camshaft. I really don't think the radix is creating enough boost where overlap is a big concern. Especially with the emissions in Cali. Overlap equals power.
01-02-2005, 08:17 PM
#18
Originally Posted by SportSide 5.3
A wide lobe seperation is a sacrifice of power for a decent idle quality. Even with a blower camshaft. I really don't think the radix is creating enough boost where overlap is a big concern. Especially with the emissions in Cali. Overlap equals power.
how much overlap to you recommend?
