Cams with -1 overlap?
02-07-2012, 07:00 AM
#63
not trying to second guess him but who knows lunati may have tried it with different lsas and decided on what they did for a reason. Im also interested in the results if he does it.
this cam is not far from what has been proven before like the 218/230 grind. Id like to see it compared to a plain 224 cam. The old 224 cam has great results even in an ls3
this cam is not far from what has been proven before like the 218/230 grind. Id like to see it compared to a plain 224 cam. The old 224 cam has great results even in an ls3
02-07-2012, 07:40 AM
#64
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How much top would I be giving up by going from 112 to 110! I figured that wouldnt even be noticable, kinda figured lunati set it 112 just for the sake a of smoother idle because its NOT a big cam.
02-07-2012, 08:18 AM
#66
well if your doing the 110 i wouldnt let them grind it with any advance in it because if you do advance it 4 degrees you looking at a 34.5 intake valve closing point which brings the power band down. Cant really say how much but it does. Maybe one of the cam techs can give you a generalization with their software programs.
02-07-2012, 08:56 AM
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Ya its a 112/108 but its only 217/228 duration so its about -1 overlap. If I do 110 it will be around +1-2 overlap.. so if they do it 110 it would would have +2 advance inseted of 4 also.
02-11-2012, 10:10 AM
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i'v read thru this topic,and it seems there is a missed theory on negative overlap cam events!
most if not all short overlap cams(including negative) are designed for TURBO engines!
when most turbos will produce high exhaust manifold pressure,higher than intake pressure,
overlap with both valves open , exhaust will flow back into inlet port and really slow down inlet flow, as well as disrupt pulse flow.
so simply close the exhaust valve before TDC, and dont open inlet until ATDC, (and use the hi-pressure of the turbo to force more air in cylinder,simple right!!!)
and it will raise mid-range TORQUE a lot, some time close to 50%.
anyway thats my take on it, and like any race project all depends on overall setup!
most if not all short overlap cams(including negative) are designed for TURBO engines!
when most turbos will produce high exhaust manifold pressure,higher than intake pressure,
overlap with both valves open , exhaust will flow back into inlet port and really slow down inlet flow, as well as disrupt pulse flow.
so simply close the exhaust valve before TDC, and dont open inlet until ATDC, (and use the hi-pressure of the turbo to force more air in cylinder,simple right!!!)
and it will raise mid-range TORQUE a lot, some time close to 50%.
anyway thats my take on it, and like any race project all depends on overall setup!
02-11-2012, 09:27 PM
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well if your doing the 110 i wouldnt let them grind it with any advance in it because if you do advance it 4 degrees you looking at a 34.5 intake valve closing point which brings the power band down. Cant really say how much but it does. Maybe one of the cam techs can give you a generalization with their software programs.
Been busting my *** working and just dont have the time to even do it, but March is dead line... time for something nice for me beside ******* work!
02-11-2012, 11:16 PM
#71
112 bud would be my choice. It's pretty damn choppy. Wish I had a video of my hot am wish was 112 too and that wasn't even a true dual like you 5th Gen guys. I looked on fquick and it was taken down sorry I'll try looking for it later but it was pretty choppy.
12-15-2012, 11:04 PM
#72
I know this is a bit old but I was just reading through... wondering what the OP ending up doing?
Corvette Forum is an interesting place to look at LS3 cams. One of the most popular there is a 230/234 114+2. It has 4 degrees of overlap and drives nice and hits close to 500rwhp on stock LS3 heads. Torque is usually in the 460 range. Say what you will about huge splits, but reversion and additional overlap just kills the drivability without substantially increasing performance from what most have seen.
As PatG said in this thread, the LS3 has a good exhaust port. Just the intake is so good, you can rely on less cam there to make more power. Or, as show in the 230/234 cam, reduce the exhaust duration so you can add more intake to create power without getting into overlap/reversion issues. I think Spin over on CF ran a 234/228 reverse split and made huge power as well. It's all about feeding the intake of those heads.
Corvette Forum is an interesting place to look at LS3 cams. One of the most popular there is a 230/234 114+2. It has 4 degrees of overlap and drives nice and hits close to 500rwhp on stock LS3 heads. Torque is usually in the 460 range. Say what you will about huge splits, but reversion and additional overlap just kills the drivability without substantially increasing performance from what most have seen.
As PatG said in this thread, the LS3 has a good exhaust port. Just the intake is so good, you can rely on less cam there to make more power. Or, as show in the 230/234 cam, reduce the exhaust duration so you can add more intake to create power without getting into overlap/reversion issues. I think Spin over on CF ran a 234/228 reverse split and made huge power as well. It's all about feeding the intake of those heads.
