ls3 cam discusion
10-20-2010, 09:30 AM
#1
ls3 cam discusion I have been fooling around with my EA program and have noticed that the ls3 heads don't like alot of dur or lift. From what I can figure out it looks as though the intake valve is to big.
On a ls3 427 ci it seems as though it likes around 230/240 dur but not much more lift than .525/.525. I know some guys are running alot more but according to my ea program there is substantial loss in power. If I sub in a smaller valve then the lift begins to make alot of diff and power igained.
Any thoughts on this from the real world as of course this is just theory.
On a ls3 427 ci it seems as though it likes around 230/240 dur but not much more lift than .525/.525. I know some guys are running alot more but according to my ea program there is substantial loss in power. If I sub in a smaller valve then the lift begins to make alot of diff and power igained.
Any thoughts on this from the real world as of course this is just theory.
10-20-2010, 01:13 PM
#2
Ok I will come at this another way. With all the factory ls3 cams and hot cams the ct525 cam makes the best poaer by alot. We have dynoed them at 560 hp@6450 with 490tq@5300-5500. The ct 525 specs are 226/236 .525/.525 on 110l/c. The ls7 has more lift but way less duration 211/233 .593/.593 lift. The ls7 would make make more power with the ct 525 cam. So stroking my ls3 to 427 ci I am in a situation that I don't know what cam to spec for a 6000 rpm hp peak. Most of the cams that I have looked at show alot more lift as soon as you increase the duration. I would rather not increase the lift alot if possible and from what I have seen teh lift really doesn't help.
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10-20-2010, 01:51 PM
#3
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10-20-2010, 02:55 PM
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You are correct that the heads don't need as much lift. My cam for example only has .620 lift but its in the 240's in and 250's ex. In designing cams you have to increase the lift of the lobe in order to increase the duration of the same lobe. This is done for idel and drivablity. You could design one like a NHRA stock class cam it would be almost square. Lots of duration with stock lift #'s. It would be hard to drive, and hard on the valve train. A good example for a cam with alot of duration and small lift is GM's ZZ3 and ZZ4 cams. They made for noisy valve trains.
These heads will move alot of air with the correct cam. These heads like aggesive ramps with wider then usual lobe seperation more exhaust duration and mild lifts. Like you stated the valves are large so you need to hold them open longer (to fill the ports)but not as high. My car revs much faster with these heads and cam then it did with the 243's and a MS3. It has more torque every where and better driveability with larger heads and just a little larger cam.
These heads will move alot of air with the correct cam. These heads like aggesive ramps with wider then usual lobe seperation more exhaust duration and mild lifts. Like you stated the valves are large so you need to hold them open longer (to fill the ports)but not as high. My car revs much faster with these heads and cam then it did with the 243's and a MS3. It has more torque every where and better driveability with larger heads and just a little larger cam.
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10-21-2010, 08:01 AM
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Sorry I was wrong about the ZZ cams they had very little duration for the amount of lift. GM built very aggresive ramps into them to make power and be emission legal. I would go to a better spring if using the stock L92 valves. The LS3 intakes weigh less. With any cam other then the stock one I would step up to a PAC 1518 behive or dual spring of your choice. I think the yellows are the stock LS3 spring. I could be wrong.
