heads breakdown
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Joined: Jun 2006
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From: San Antonio, TX
heads breakdown I know this has probably been asked before, but i was wondering if anyone could name all the heads used on GEN III small blocks, and which ones came on what motors. if theres a thread on this, could someone post the link? thanks 
1998 = 806
1999 - 2000.5 = 853
2000.5 - 2004 = 241
2001-2004 LS6 = 243
https://ls1tech.com/forums/showthrea...ight=241+heads
1999 - 2000.5 = 853
2000.5 - 2004 = 241
2001-2004 LS6 = 243
https://ls1tech.com/forums/showthrea...ight=241+heads
Heads
GM has used several different heads on these engines, depending on both the year and the application. They're made of cast iron or aluminum and they come with a variety of chambers and ports, so they're not all interchangeable even though you can bolt them on any of the blocks. These heads are unique because they have "cathedral intake ports" that are tall and narrow instead of the rectangular design we're all used to seeing. GM spent a lot of time designing the heads with "replicated ports," making sure that all the intake ports and exhaust ports were identical to each other so the airflow was exactly the same for every cylinder. The tall ports allowed them to target the injectors for the best possible spray pattern on the back of the intake valve, too. These heads are the key to the success of the Gen III motors and the horsepower they make.
Although all these heads look very similar, there are significant differences:
4.8L/5.3L Trucks
Both of these engines share a common aluminum head with 71cc chambers.. The 12559862 casting was used from '99-'04, but the 12561706 showed up on some engines in '04, too. The 862 casting came with and without the recess on the edge of the deck surface, so rebuilders need to make sure they use the right head gasket when installing one of these heads.
5.7L Cars
There have been three different heads used on the 5.7L motors.
*
'97-'98 LS1 - The original LS1 heads were 10215339 or 12558806 castings that had 66.7cc chambers and nine bolts around the perimeter to hold the rocker covers on. These early heads are unique because they had a recessed area right below the No. 3 or No. 6 cylinder, so rebuilders must use the early style, composition head gaskets with them. If the later MLS gaskets are installed with the heads that have the recess, the engine will leak coolant to the outside from the recessed area in the deck surface.
*
'99-'04 LS1 - The LS1 switched to center-bolt rocker covers in '99, so these engines came with a new head. This 12559853 casting was used up through '01, but the 12564241 was also found on some engines beginning in '01. We're told that these heads didn't have the recessed area on the outer edge, so the MLS gasket should work okay, but the parts book calls for the composition gasket up through '01 so that's probably what you should use. These heads have 66.7cc chambers, too.
*
'01-'04 LS6 - The LS6 performance engines had the 12564243 castings that flowed more air due to better intake ports and the "Dee" shaped exhaust ports. The chamber was a little smaller (61.15cc) so the engine had a slightly higher compression ratio, too.
6.0L Cars and Trucks
There have been two heads used on the regular 6.0L engine along with a third one that was used only on the engines that were designed to run on natural gas.
*
The cast iron head on the '99-'01 engines was a 12561873 casting.
*
All of the '01- '04 6.0L engines had an aluminum head with a 12562317 or 12572035 casting number. These heads were used on all the 6.0L motors including the standard LQ4 and the LQ9 performance motor. They're easy to recognize because they have the same "Dee" shaped exhaust ports that were found on the LS6 heads.
*
All of the 6.0L heads have 71cc chambers.
*
GM offered a 6.0L engine for natural gas applications so there's a 12562317 casting with special valves and seats, too. This head can be identified by the unique pattern of bumps found on the rocker rail (see the story, including photo and chart, in last month's "Core Corner" Engine Builder, March 2005, page 20).
GM has used several different heads on these engines, depending on both the year and the application. They're made of cast iron or aluminum and they come with a variety of chambers and ports, so they're not all interchangeable even though you can bolt them on any of the blocks. These heads are unique because they have "cathedral intake ports" that are tall and narrow instead of the rectangular design we're all used to seeing. GM spent a lot of time designing the heads with "replicated ports," making sure that all the intake ports and exhaust ports were identical to each other so the airflow was exactly the same for every cylinder. The tall ports allowed them to target the injectors for the best possible spray pattern on the back of the intake valve, too. These heads are the key to the success of the Gen III motors and the horsepower they make.
Although all these heads look very similar, there are significant differences:
4.8L/5.3L Trucks
Both of these engines share a common aluminum head with 71cc chambers.. The 12559862 casting was used from '99-'04, but the 12561706 showed up on some engines in '04, too. The 862 casting came with and without the recess on the edge of the deck surface, so rebuilders need to make sure they use the right head gasket when installing one of these heads.
5.7L Cars
There have been three different heads used on the 5.7L motors.
*
'97-'98 LS1 - The original LS1 heads were 10215339 or 12558806 castings that had 66.7cc chambers and nine bolts around the perimeter to hold the rocker covers on. These early heads are unique because they had a recessed area right below the No. 3 or No. 6 cylinder, so rebuilders must use the early style, composition head gaskets with them. If the later MLS gaskets are installed with the heads that have the recess, the engine will leak coolant to the outside from the recessed area in the deck surface.
*
'99-'04 LS1 - The LS1 switched to center-bolt rocker covers in '99, so these engines came with a new head. This 12559853 casting was used up through '01, but the 12564241 was also found on some engines beginning in '01. We're told that these heads didn't have the recessed area on the outer edge, so the MLS gasket should work okay, but the parts book calls for the composition gasket up through '01 so that's probably what you should use. These heads have 66.7cc chambers, too.
*
'01-'04 LS6 - The LS6 performance engines had the 12564243 castings that flowed more air due to better intake ports and the "Dee" shaped exhaust ports. The chamber was a little smaller (61.15cc) so the engine had a slightly higher compression ratio, too.
6.0L Cars and Trucks
There have been two heads used on the regular 6.0L engine along with a third one that was used only on the engines that were designed to run on natural gas.
*
The cast iron head on the '99-'01 engines was a 12561873 casting.
*
All of the '01- '04 6.0L engines had an aluminum head with a 12562317 or 12572035 casting number. These heads were used on all the 6.0L motors including the standard LQ4 and the LQ9 performance motor. They're easy to recognize because they have the same "Dee" shaped exhaust ports that were found on the LS6 heads.
*
All of the 6.0L heads have 71cc chambers.
*
GM offered a 6.0L engine for natural gas applications so there's a 12562317 casting with special valves and seats, too. This head can be identified by the unique pattern of bumps found on the rocker rail (see the story, including photo and chart, in last month's "Core Corner" Engine Builder, March 2005, page 20).
