Whats the difference between the 241 and 243 castings?

 

241 is LS1 casting and 243 is Ls6....i believe...

 

Sounds right to me.

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:

 

Casting Number 243
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

 

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.

 

That's exactly what I was looking for. Thanks.

I wondered about the Intake Port volume especially...

 

The 97-98 806 castings will be the perimeter while all other 99-up heads will be center bolt. If you are going to be looking at ported heads, make sure to ask about the runner volume after porting. It can vary greatly. We have seen ported LS1 heads with runner volumes larger than our LS6 style heads.

 

Thanks, Gunnar. That seems like it might be counter-productive on a 346 that's not blown or sprayed... I was trying to decide whether to port my stock heads, since I have the 241's, or to buy a set of ported and polished 243's (or LS6 style heads) outright. I wanted to keep the velocity up, so I was concerened about getting the intake runner volume upwards of 225cc's, where I'll lose some mid-range torque. I have 4.10's and I'm not too worried about losing low-end torque. I guess if I buy new ones, I can sell my 241's to help pay for the upgrade...

 

Make sure to take a look at our 243 catings that we have right now.

 

Yeah, I read a bunch of posts about them, and it sounds like a sweet deal with those valves. I couldn't find the page for them on your web site, though. Just the LS6 Style and 5.3/LS1 pages...

 

Tehy aren't on there. Haven't had time to go on and add them in. If you have any questions about them, please let us know.

 

LS6 on the left and LS1 on the right:



vs. this from AFR:



and the new LS7: