So LS7 do come with Forged pistons?
10-12-2005, 04:21 PM
#1
Teching In
Thread Starter
Join Date: Jun 2004
Location: Sunnyvale, CA
Posts: 32
Likes: 0
Received 0 Likes
on
0 Posts
So LS7 do come with Forged pistons? I remember reading from a member that said Ls7 don't come with forged pistons. I just read Car and Driver and it states that they DO come with forged pistons....So, I don't know who right? here's what I read:
PS. Look on paragraph 5
AUGUST 14, 2005
2006 Chevrolet Corvette Z06
1 2 3
Simply the fastest-ever production Vette.
BY CSABA CSERE
PHOTOGRAPHY BY AARON KILEY
February 2005
Web Exclusive!
An interactive look at the comprehensive attention to detail that makes the Z06 remarkable
The number is magic, recalling the era when Detroit dominated the world with its big, powerful, swaggering V-8s. The Chevrolet 427 V-8 first appeared as an experimental engine that powered Junior Johnson to a then-amazing 166-mph lap at Daytona in 1963. It went into production soon afterward, known variously as the Mark IV, the Chevy big-block, or simply the rat motor.
Now the 427 is back, powering the fire-breathing 2006 Z06 Corvette. Okay, so the engine actually displaces 427.6 cubic inches (7008cc), about one more cubic inch than the original. That's because this new 427 is not a reincarnation of the old rat motor. Instead, it's yet another variant of the versatile mouse motor, the small-block Chevy V-8 that is celebrating its 50th birthday this year. Even so, it's rated at 500 horsepower-more than any of the bygone 427s and 454s-and these are SAE net horses, not the bogus gross ponies from the '60s.
This V-8, dubbed the LS7, is based on the latest incarnation of the small-block architecture, which GM calls Gen IV. However, virtually every component has been reengineered to achieve the greater displacement and higher output.
Compared with the LS2-the base C6 engine-the LS7 has a new block with a bore of 4.13 inches and a stroke of 4.00 inches (versus 4.00-by-3.62 inches). To accommodate the larger holes with the standard 4.4-inch bore spacing, Chevy engineers switched from the LS2's cast-in-iron liners to thinner pressed-in liners.
Within the LS7 block, you'll find a forged-steel crankshaft, forged-steel main-bearing caps, titanium connecting rods, and forged pistons. A dry-sump oiling system with an eight-quart reservoir ensures proper lubrication of this long-stroke engine at its 7000-rpm redline.
Making high-rpm power with just two valves per large cylinder requires optimized breathing at every stage of the intake and exhaust process. This starts with a low-restriction air cleaner and intake ducting feeding a throttle body 3.5 inches in diameter. A composite intake manifold funnels the air to unique cylinder heads with massive intake and exhaust ports, which are CNC-machined for consistent shape and contour. These ports feed lightweight 2.20-inch titanium intake valves and 1.61-inch exhausts, with sodium-filled stems for superior high-temperature durability.
The valves are positioned at 12 degrees from the cylinder bores. This angle provides better breathing and a more compact combustion chamber than the LS2's 15-degree angle does. Valve lift is a hefty 0.591 inch, using rocker arms with a 1.8:1 ratio.
An 11.0:1 compression ratio extracts maximum energy from this heavy breathing, and the products of combustion are efficiently expelled via hydroformed headers that feed two rear-mounted mufflers via giant 3.0-inch-diameter exhaust pipes.
Due to rising costs, those mufflers are steel instead of titanium, as they were on the previous Z06, but they are sophisticated in a different way. At low revs, all the exhaust goes through a single well-muffled tailpipe in each muffler. When you stomp on the throttle and exceed 3500 rpm, however, vacuum-powered bypasses open up a second, virtually straight-through tailpipe in each muffler. That sound will be worth the wait.
The maximum of 500 horsepower is developed at 6200 rpm, and peak torque is 475 pound-feet at 4800 rpm. Clearly, this V-8, which is assembled at GM's new Performance Build Center in Wixom, Michigan, is tuned for high rpm. But with about 385 pound-feet-the peak torque of the new BMW M5 V-10 at 6100 rpm-available at about 1600 revs, the LS7 should be plenty tractable.
This output goes though a high-capacity clutch to a beefed-up version of the Corvette's six-speed, rear-mounted transaxle. One addition is a pump that sends the transmission oil forward to the engine radiator for cooling. The cooled oil flows through a second heat exchanger to control the temperature of the differential lubricant before returning to the transmission.
.....So there you have it. Like I said I am only putting up because I remember seeing a comment from a member that said they don't come with forged pistons.... It seems that they do, although they could also be wrong. What do you guys think/know?
PS. Look on paragraph 5
AUGUST 14, 2005
2006 Chevrolet Corvette Z06
1 2 3
Simply the fastest-ever production Vette.
BY CSABA CSERE
PHOTOGRAPHY BY AARON KILEY
February 2005
Web Exclusive!
An interactive look at the comprehensive attention to detail that makes the Z06 remarkable
The number is magic, recalling the era when Detroit dominated the world with its big, powerful, swaggering V-8s. The Chevrolet 427 V-8 first appeared as an experimental engine that powered Junior Johnson to a then-amazing 166-mph lap at Daytona in 1963. It went into production soon afterward, known variously as the Mark IV, the Chevy big-block, or simply the rat motor.
Now the 427 is back, powering the fire-breathing 2006 Z06 Corvette. Okay, so the engine actually displaces 427.6 cubic inches (7008cc), about one more cubic inch than the original. That's because this new 427 is not a reincarnation of the old rat motor. Instead, it's yet another variant of the versatile mouse motor, the small-block Chevy V-8 that is celebrating its 50th birthday this year. Even so, it's rated at 500 horsepower-more than any of the bygone 427s and 454s-and these are SAE net horses, not the bogus gross ponies from the '60s.
This V-8, dubbed the LS7, is based on the latest incarnation of the small-block architecture, which GM calls Gen IV. However, virtually every component has been reengineered to achieve the greater displacement and higher output.
Compared with the LS2-the base C6 engine-the LS7 has a new block with a bore of 4.13 inches and a stroke of 4.00 inches (versus 4.00-by-3.62 inches). To accommodate the larger holes with the standard 4.4-inch bore spacing, Chevy engineers switched from the LS2's cast-in-iron liners to thinner pressed-in liners.
Within the LS7 block, you'll find a forged-steel crankshaft, forged-steel main-bearing caps, titanium connecting rods, and forged pistons. A dry-sump oiling system with an eight-quart reservoir ensures proper lubrication of this long-stroke engine at its 7000-rpm redline.
Making high-rpm power with just two valves per large cylinder requires optimized breathing at every stage of the intake and exhaust process. This starts with a low-restriction air cleaner and intake ducting feeding a throttle body 3.5 inches in diameter. A composite intake manifold funnels the air to unique cylinder heads with massive intake and exhaust ports, which are CNC-machined for consistent shape and contour. These ports feed lightweight 2.20-inch titanium intake valves and 1.61-inch exhausts, with sodium-filled stems for superior high-temperature durability.
The valves are positioned at 12 degrees from the cylinder bores. This angle provides better breathing and a more compact combustion chamber than the LS2's 15-degree angle does. Valve lift is a hefty 0.591 inch, using rocker arms with a 1.8:1 ratio.
An 11.0:1 compression ratio extracts maximum energy from this heavy breathing, and the products of combustion are efficiently expelled via hydroformed headers that feed two rear-mounted mufflers via giant 3.0-inch-diameter exhaust pipes.
Due to rising costs, those mufflers are steel instead of titanium, as they were on the previous Z06, but they are sophisticated in a different way. At low revs, all the exhaust goes through a single well-muffled tailpipe in each muffler. When you stomp on the throttle and exceed 3500 rpm, however, vacuum-powered bypasses open up a second, virtually straight-through tailpipe in each muffler. That sound will be worth the wait.
The maximum of 500 horsepower is developed at 6200 rpm, and peak torque is 475 pound-feet at 4800 rpm. Clearly, this V-8, which is assembled at GM's new Performance Build Center in Wixom, Michigan, is tuned for high rpm. But with about 385 pound-feet-the peak torque of the new BMW M5 V-10 at 6100 rpm-available at about 1600 revs, the LS7 should be plenty tractable.
This output goes though a high-capacity clutch to a beefed-up version of the Corvette's six-speed, rear-mounted transaxle. One addition is a pump that sends the transmission oil forward to the engine radiator for cooling. The cooled oil flows through a second heat exchanger to control the temperature of the differential lubricant before returning to the transmission.
.....So there you have it. Like I said I am only putting up because I remember seeing a comment from a member that said they don't come with forged pistons.... It seems that they do, although they could also be wrong. What do you guys think/know?
10-13-2005, 12:11 PM
#5
Teching In
Join Date: Mar 2004
Location: Nashville
Posts: 32
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by chuntington101
all the stuff i have read has said cast pistons. and why would they use forged???
Chris.
Chris.
I read the forged piston caused too much piston slap at cold start that is why they went with the cast. Also, I believe there is an emissions issue that was mentioned in another thread...I will try to find it and link here
10-14-2005, 12:10 AM
#6
11 Second Club
iTrader: (4)
Join Date: Aug 2004
Location: Rockland County, NY
Posts: 1,832
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by vetdrms
I read the forged piston caused too much piston slap at cold start that is why they went with the cast. Also, I believe there is an emissions issue that was mentioned in another thread...I will try to find it and link here
10-14-2005, 06:40 AM
#7
Originally Posted by vetdrms
I read the forged piston caused too much piston slap at cold start that is why they went with the cast. Also, I believe there is an emissions issue that was mentioned in another thread...I will try to find it and link here
thanks Chris.
