Vortec L31 cylinder head
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==Design limitations and modifications== | ==Design limitations and modifications== | ||
| − | Based on info from Gary Penn, of GMPP. This is | + | Based on info from Gary Penn, of GMPP. This is an excerpt from '''Part 4'''. Parts 1-4 can be seen in their entirety '''[http://www.nastyz28.com/forum/showthread.php?t=56505 here]''', beginning at post #4: |
| − | + | :Out of the box, 0.480” valve lift, 350-400 HP dependant on the CR, cam, ring seal, oil control, etc. | |
| − | More than 0.480” lift cut the guides down to clear the retainers. | + | :More than 0.480” lift cut the guides down to clear the retainers. |
| − | Generally speaking, Vortec's stall at between 0.500” and 0.550” valve lift. This is where flow actually begins to decrease. But their true strength is low lift flow which gives more area under the total flow curve. And if you think about it how long are your valves at peak lift? They spend much more time at 0.400” and below, where the Vortec’s outperform most other heads. | + | :Generally speaking, Vortec's stall at between 0.500” and 0.550” valve lift. This is where flow actually begins to decrease. But their true strength is low lift flow which gives more area under the total flow curve. And if you think about it how long are your valves at peak lift? They spend much more time at 0.400” and below, where the Vortec’s outperform most other heads. |
| − | Unported, with all the other tricks in place, the Vortec’s will flow about 235-240 CFM at 0.500” intake and 165-170 cfm at 0.500” exhaust, on a 4" bore at 28" H2O, with clay radiused port opening. With some careful porting there is another 5-10 CFM or so to be had. But again the low lift numbers are unsurpassed at 0.100”, 0.200”, 0.300”, etc. lift. For example the Vortec’s flow as much air at 0.400” as 0.500”, and no 23 degree head that I'm aware of can match them at 0.200”-0.300” lift for the combination of flow and swirl. Even the GM Fast Burn head can't touch them at low lift, its ports are too big (flow is similar, swirl is less), it does of course out perform them at lift over 0.500”. | + | :Unported, with all the other tricks in place, the Vortec’s will flow about 235-240 CFM at 0.500” intake and 165-170 cfm at 0.500” exhaust, on a 4" bore at 28" H2O, with clay radiused port opening. With some careful porting there is another 5-10 CFM or so to be had. But again the low lift numbers are unsurpassed at 0.100”, 0.200”, 0.300”, etc. lift. For example the Vortec’s flow as much air at 0.400” as 0.500”, and no 23 degree head that I'm aware of can match them at 0.200”-0.300” lift for the combination of flow and swirl. Even the [http://www.gmpartsdirect.com/performance_parts/store/catalog/Product.jhtmlPRODID=680&CATID=671.html GM Fast Burn head] can't touch them at low lift, its ports are too big (flow is similar, swirl is less), it does of course out perform them at lift over 0.500”. |
| − | Unported Vortec’s with the "tricks" can produce 500 HP on well built, high CR, drag race short block. 425-450 HP is more realistic for a killer street engine running on pump gas. | + | :Unported Vortec’s with the "tricks" can produce 500 HP on well built, high CR, drag race short block. 425-450 HP is more realistic for a killer street engine running on pump gas. |
| − | ==Flow rate of L31 Vortec | + | ==Flow rate of L31 Vortec heads== |
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!Lift (inches) !!Intake (CFM) !!Exhaust (CFM) | !Lift (inches) !!Intake (CFM) !!Exhaust (CFM) | ||
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