Difference between 241 and 243 castings?

To add on to this a bit... The 243 makes a higher compression and flows better.
LS6 on the left and LS1 on the right:
Head: 2001 LS6 5.7 Litre Passenger Car
Material: Aluminimum
Part Number:
12564243
Combustion Chamber Volume: 64.45cc
Compression Ratio: 10.5:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches
Casting Number 241
Head: 1997+ LS1 5.7 Litre Passenger Car
Material: Aluminimum
Part Number:
12559806 (1997-98) Chambers = 69cc
12559853 (1999-00)
12564241 (2001-03)
Combustion Chamber Volume: 66.67cc
Compression Ratio: 10.1:1
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches
To add on to this a bit... The 243 makes a higher compression and flows better.
LS6 on the left and LS1 on the right:

True.....
The 243 casting is also used on the LS2 motor. It is interchangeable with the LS1, LS6, LS2, 6.0, 5.3, and 4.8 motor's as all the heads just listed bolt on to eachother's bottomend.
The LS6 head is a 64cc head where as the LS1 (241 casting as well as 806, and 853 casting) is a 67.67cc's. The difference is compression.
The 64 cc head will give about 1/2 a point more compression on a stcok LS1/LS6 motor.
There is a ton of reading on this subject. Check out JRP's common asked questions and read until your eyes fall out.
Head: 2001 LS6 5.7 Litre Passenger Car
Material: Aluminimum
Part Number:
12564243
Combustion Chamber Volume: 64.45cc
Compression Ratio: 10.5:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches
Casting Number 241
Head: 1997+ LS1 5.7 Litre Passenger Car
Material: Aluminimum
Part Number:
12559806 (1997-98) Chambers = 69cc
12559853 (1999-00)
12564241 (2001-03)
Combustion Chamber Volume: 66.67cc
Compression Ratio: 10.1:1
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches
I wondered about the Intake Port volume especially...
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