233/276@.050 Why GM?
12-30-2005, 05:45 PM
#1
233/276@.050 Why GM? Why does GM use extreme split profile cams for the LS7? Aftermarket cam grinders use much less split.
Stock LS7 cam duration @.050 211/230
New GM HOT CAM stage 2 : @.050 227/239
New GM HOT CAM stage 3 : @.050 233/276
Stock LS7 cam duration @.050 211/230
New GM HOT CAM stage 2 : @.050 227/239
New GM HOT CAM stage 3 : @.050 233/276
12-30-2005, 06:54 PM
#3
That Stage 3 looks like a misprint. 276 @ .050" has no hope of clearing the pistons, unless they have HUGE valve reliefs.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2018 Cadillac Escalade 6.2L A10 Pat G tuned.
LS1,LS2,LS3,LS7,LT1 Custom Camshaft Specialist For custom camshaft help press here.
Custom LSX tuning in person or via email press here.
12-30-2005, 06:58 PM
#4
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Originally Posted by Patrick G
That Stage 3 looks like a misprint. 276 @ .050" has no hope of clearing the pistons, unless they have HUGE valve reliefs.
4 would make much more sense.
227/239
233/246
12-30-2005, 07:02 PM
#5
Originally Posted by Pwebbz28
My guess is to help overcome restrictive exhaust as compared to headers.
It (large split) simply makes more power while using headers/mufflers or open exhaust in the LS7 or LS1 motor.
12-30-2005, 07:16 PM
#7
Originally Posted by Patrick G
That Stage 3 looks like a misprint. 276 @ .050" has no hope of clearing the pistons, unless they have HUGE valve reliefs.
Timing per HOT ROD mag @.050-inch lift(degrees)
Intake: opens 6 atdc / closes 47 abdc = total 233@.050
Exhaust: opens 63 bbdc / closes 33 btdc = total 276@.050
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12-30-2005, 07:28 PM
#9
I do not know if it is a misprint either. The pistons do have pretty healthy valve reliefs. They did change out the retainer in that test to get more installed height from the stock springs because of the high lift of the cam. I took it that these cams are newly developed cams...just using the same name? If you look at the exhaust flow figures in the Hot Rod article it makes you believe that the intake/exhaust ratio is very heavy towards the intake side...so that part would fit in with the extreme difference in exhaust duration. I bet it has to do with emissions.
12-30-2005, 07:52 PM
#10
If you look at the valve events instead of duration it all makes sense.
The EVO is where it should be (remember the 115 deg CL. The IVC is where it should be. Remember the 123 deg CL.
What happened is they smashed the overlap. Look how late the intake opens. Its like a cam 10 degrees smaller than it should be.
The answer is probably emissions.
The EVO is where it should be (remember the 115 deg CL. The IVC is where it should be. Remember the 123 deg CL.
What happened is they smashed the overlap. Look how late the intake opens. Its like a cam 10 degrees smaller than it should be.
The answer is probably emissions.
12-31-2005, 06:21 PM
#11
Originally Posted by DavidNJ
If you look at the valve events instead of duration it all makes sense.
The EVO is where it should be (remember the 115 deg CL. The IVC is where it should be. Remember the 123 deg CL.
What happened is they smashed the overlap. Look how late the intake opens. Its like a cam 10 degrees smaller than it should be.
The answer is probably emissions.
The EVO is where it should be (remember the 115 deg CL. The IVC is where it should be. Remember the 123 deg CL.
What happened is they smashed the overlap. Look how late the intake opens. Its like a cam 10 degrees smaller than it should be.
The answer is probably emissions.
I bet a cam ground to stage 2 specs would be awsome in a higher compression 347 LS1.
