427 Heads (C5R vs. LS7)
427 Heads (C5R vs. LS7) Are the LS7 heads superior to the current C5R heads out right now? It seems by the looks of the info coming out the LS7 is gonna be a notch above the existing hardware out right now. But I'd like your guys opinions on them and what exactly makes them better. Also It'd be nice to get a breakdown of whats superior from the C5R longblock to the LS7.
Teching In
Joined: Aug 2004
Posts: 47
Likes: 0
One of the greatest advantages for those intending to upgrade an LS1/LS6 engine will be the availability of a factory intake manifold to work with the LS7 heads. The need for a sheet metal manifold (along with the price of the C5R heads) was a turnoff, so I've made do with Stage IV LS6s. But not for too much longer.
This topic was in another thread, but it seems that the LS7 heads may be better than the C5R heads. Could be a CNC ported C5R head. The C5R flows 340 and the LS7 is 360, and I believe it has bigger valves;
Mechanical Mastery
A substantial increase in torque, particularly lower in the rpm range, is endemic when considering large displacement. Carry that torque curve hard up the rpm range, and the result is horsepower in magnanimous excess. That's easier said than done, requiring hedonistic cylinder-filling efficiency to provide for the displacement-draw of large cubes at high rpm. It takes an extraordinary set of heads. The cylinder heads of the LS7 are nothing short of magnificent.
Taking the racing cues of a higher port entry and a flatter valve angle, the intake ports have been substantially raised at the manifold face, while the valve angle has been changed from the 15-degree angle of other engines in this family, to a more advantageous 12-degrees. The ports themselves have been significantly enlarged, aided by the use of offset intake rockers, moving the pushrods adjacent to the intake runners outward. The pushrod pinch, commonly a point of cross sectional constriction in the intake ports has been eliminated. Overall, the port cross section has been enlarged, in keeping with the requirements of high-rpm torque production with a large displacement engine.
The intake valve diameter has been increased to a big-block-like 2.200-inches, while the exhaust measures 1.610-inchs, and the valve stems have been lengthened. The longer valves facilitate port design, provide the room for deep ports in the bowl and short turn, as well as allowing for greater valve lift and more valvespring installed height. The finishing touch is in the ports' shape, masterfully CNC-carved into the cast metal, reportedly a design collaboration of GM engineers and distinguished race cylinder head man Mike Chapman of Chapman Racing Heads. CNC sculpting is also visible in the combustion chamber, with a smooth gradual contour to the deck further enhancing flow.
The list of features is impressive, and so is the airflow, reportedly pegging the manometer at 360 cfm on the intake and 210 cfm on the exhaust, as measured at the LS7's maximum valve lift. Intake airflow is up some 43 percent over the LS6 head, while the exhaust shows a 26 percent gain. In terms of flow capacity, that's serious territory, far beyond any factory Chevy smallblock head of the past, and well past any production big-block heads. As a measure of comparison, a decent high-performance aftermarket head for the standard smallblock Chevy will typically flow around 100 cfm less than the production LS7 intake, and only the most exotic race two-valve heads compare. The LS7 heads just cook the books on anything we've seen in the past.
http://popularhotrodding.com/tech/0504phr_ls7/
Mechanical Mastery
A substantial increase in torque, particularly lower in the rpm range, is endemic when considering large displacement. Carry that torque curve hard up the rpm range, and the result is horsepower in magnanimous excess. That's easier said than done, requiring hedonistic cylinder-filling efficiency to provide for the displacement-draw of large cubes at high rpm. It takes an extraordinary set of heads. The cylinder heads of the LS7 are nothing short of magnificent.
Taking the racing cues of a higher port entry and a flatter valve angle, the intake ports have been substantially raised at the manifold face, while the valve angle has been changed from the 15-degree angle of other engines in this family, to a more advantageous 12-degrees. The ports themselves have been significantly enlarged, aided by the use of offset intake rockers, moving the pushrods adjacent to the intake runners outward. The pushrod pinch, commonly a point of cross sectional constriction in the intake ports has been eliminated. Overall, the port cross section has been enlarged, in keeping with the requirements of high-rpm torque production with a large displacement engine.
The intake valve diameter has been increased to a big-block-like 2.200-inches, while the exhaust measures 1.610-inchs, and the valve stems have been lengthened. The longer valves facilitate port design, provide the room for deep ports in the bowl and short turn, as well as allowing for greater valve lift and more valvespring installed height. The finishing touch is in the ports' shape, masterfully CNC-carved into the cast metal, reportedly a design collaboration of GM engineers and distinguished race cylinder head man Mike Chapman of Chapman Racing Heads. CNC sculpting is also visible in the combustion chamber, with a smooth gradual contour to the deck further enhancing flow.
The list of features is impressive, and so is the airflow, reportedly pegging the manometer at 360 cfm on the intake and 210 cfm on the exhaust, as measured at the LS7's maximum valve lift. Intake airflow is up some 43 percent over the LS6 head, while the exhaust shows a 26 percent gain. In terms of flow capacity, that's serious territory, far beyond any factory Chevy smallblock head of the past, and well past any production big-block heads. As a measure of comparison, a decent high-performance aftermarket head for the standard smallblock Chevy will typically flow around 100 cfm less than the production LS7 intake, and only the most exotic race two-valve heads compare. The LS7 heads just cook the books on anything we've seen in the past.
http://popularhotrodding.com/tech/0504phr_ls7/
The LS7 cylinder heads are a new design, and come fully CNC ported, setting a new benchmark for 2-valve performance. These heads are a key to the LS7's power production, with intake flow rates up 43 percent compared to the LS6/LS2 cylinder heads, while the exhaust notches up for a 26percent gain. These are serious cylinder heads, even by hardcore hot-rodder standards, and are far beyond anything ever seen in production.
Launching!
Joined: Mar 2004
Posts: 222
Likes: 0
From: Ontario Canada
There are C5R heads that flow around 400cfm but I think at much higher lift like .700 or .750 so this would mean the LS7 heads should be better for street applications with a hydraulic cam and .600 lift.
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Originally Posted by LS7SS
There are C5R heads that flow around 400cfm but I think at much higher lift like .700 or .750 so this would mean the LS7 heads should be better for street applications with a hydraulic cam and .600 lift.
http://www.gearchatter.com/viewtopic11203.php
TECH Addict
Joined: Jul 2002
Posts: 2,261
Likes: 0
Originally Posted by 11 Bravo
The LS7 cylinder heads are a new design, and come fully CNC ported, setting a new benchmark for 2-valve performance. These heads are a key to the LS7's power production, with intake flow rates up 43 percent compared to the LS6/LS2 cylinder heads, while the exhaust notches up for a 26percent gain. These are serious cylinder heads, even by hardcore hot-rodder standards, and are far beyond anything ever seen in production.
I spoke with Mike Chapman on the phone yesterday and he reiterated that the 360cfm intake was at the current cam's max intake lift in the 0.580/590" range and that these heads continue to increase in flow beyond this point :>) He further stated that a quick camshaft change to something lumpy the way we like would reap additional big power.
He also stated that the mid-lift flow was killer on these heads, however, politely declined to offer specific numbers citing that GM should be the ones to release data on these heads and not himself. I can respect that. He also believed that these heads were a maxed out effort based on the LS7 casting and that there wasn't anything left to tweak out of these heads.
When I asked him about the C5R heads compared to these, he said that these castings are significantly lighter than the C5R's and that they are not the exact same configuration as far as runner sizing and combustion chambers.
He also stated that the mid-lift flow was killer on these heads, however, politely declined to offer specific numbers citing that GM should be the ones to release data on these heads and not himself. I can respect that. He also believed that these heads were a maxed out effort based on the LS7 casting and that there wasn't anything left to tweak out of these heads.
When I asked him about the C5R heads compared to these, he said that these castings are significantly lighter than the C5R's and that they are not the exact same configuration as far as runner sizing and combustion chambers.
Originally Posted by Big-DEN
TEA will definately tell us if there is miore.
What is the intake mani doing? It was nice to see that the runners
arre an extension of the head port complete with the correct taper, etc...
What is the intake mani doing? It was nice to see that the runners
arre an extension of the head port complete with the correct taper, etc...