Difference between 241, 243 and 853 heads??
Race Director
Joined: Oct 2002
Posts: 16,477
Likes: 26
From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
853 and 241 are basically identical.
853 was used on 99-00 LS1 engines.
241 was used on 01-04 LS1 engines.
They both have a 66.67 cc combustion chamber (10.1 CR), 200cc intake runners, and 70cc (round) exhaust ports.
The 243 head is the 01+ LS6/LS2 head.
It has a smaller 64.45cc chamber for more compression (10.5 CR on LS6), 210cc intake runners, and 75cc D-shaped exhaust ports.
All three came with 2.00" intake valves, and 1.55" exhaust valves.
Of the three, the 243 (Z06) head is the most desirable for flow, and is the most popular base for further porting/modifying. Not many people mess with porting LS1 heads anymore.
And FYI for the ones you didn't mention...
5.3 truck heads (casting #862 and 706) are also a very popular base casting for porting/modifying, due to their even smaller (61.15cc) chamber size which raises compression when used on a LS1/6 engine..
6.0 truck heads (casting #317) are popular heads with the forced induction crowd, as they are basically the same as 243 heads, but with larger 71.06cc chamber size, which lowers compression when used on a LS1/6 engine.
853 was used on 99-00 LS1 engines.
241 was used on 01-04 LS1 engines.
They both have a 66.67 cc combustion chamber (10.1 CR), 200cc intake runners, and 70cc (round) exhaust ports.
The 243 head is the 01+ LS6/LS2 head.
It has a smaller 64.45cc chamber for more compression (10.5 CR on LS6), 210cc intake runners, and 75cc D-shaped exhaust ports.
All three came with 2.00" intake valves, and 1.55" exhaust valves.
Of the three, the 243 (Z06) head is the most desirable for flow, and is the most popular base for further porting/modifying. Not many people mess with porting LS1 heads anymore.
And FYI for the ones you didn't mention...
5.3 truck heads (casting #862 and 706) are also a very popular base casting for porting/modifying, due to their even smaller (61.15cc) chamber size which raises compression when used on a LS1/6 engine..
6.0 truck heads (casting #317) are popular heads with the forced induction crowd, as they are basically the same as 243 heads, but with larger 71.06cc chamber size, which lowers compression when used on a LS1/6 engine.
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
Someone may correct me if I'm wrong I believe there is a difference. From what I understand the 241s have a different design in regards to their intake runners that allows for more efficient air flow, more velocity. Also, I thought the 853s have a larger combustion chamber, lowering compression.
Racer
Joined: Jun 2007
Posts: 392
Likes: 1
From: TX
'02-'04 LS6 243 heads found in the Z06 and CTS-V also had the sodium filled (read lightweight) valvles in them. The LS2 243 heads, found on the '05-up LS2's, are the same LS6 head but with solid stem valves in them. Hope this helps! 
Also I belive 806 was the casting number on the '97-'98 LS1 heads...
Also I belive 806 was the casting number on the '97-'98 LS1 heads...
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Le Mans Master
Joined: Aug 2004
Posts: 9,420
Likes: 8
From: Southern New Jersey, The wet part at the bottom
St. Jude Donor '08-'09-'10
853 and 241 are basically identical.
853 was used on 99-00 LS1 engines.
241 was used on 01-04 LS1 engines.
They both have a 66.67 cc combustion chamber (10.1 CR), 200cc intake runners, and 70cc (round) exhaust ports.
The 243 head is the 01+ LS6/LS2 head.
It has a smaller 64.45cc chamber for more compression (10.5 CR on LS6), 210cc intake runners, and 75cc D-shaped exhaust ports.
All three came with 2.00" intake valves, and 1.55" exhaust valves.
Of the three, the 243 (Z06) head is the most desirable for flow, and is the most popular base for further porting/modifying. Not many people mess with porting LS1 heads anymore.
And FYI for the ones you didn't mention...
5.3 truck heads (casting #862 and 706) are also a very popular base casting for porting/modifying, due to their even smaller (61.15cc) chamber size which raises compression when used on a LS1/6 engine..
6.0 truck heads (casting #317) are popular heads with the forced induction crowd, as they are basically the same as 243 heads, but with larger 71.06cc chamber size, which lowers compression when used on a LS1/6 engine.
853 was used on 99-00 LS1 engines.
241 was used on 01-04 LS1 engines.
They both have a 66.67 cc combustion chamber (10.1 CR), 200cc intake runners, and 70cc (round) exhaust ports.
The 243 head is the 01+ LS6/LS2 head.
It has a smaller 64.45cc chamber for more compression (10.5 CR on LS6), 210cc intake runners, and 75cc D-shaped exhaust ports.
All three came with 2.00" intake valves, and 1.55" exhaust valves.
Of the three, the 243 (Z06) head is the most desirable for flow, and is the most popular base for further porting/modifying. Not many people mess with porting LS1 heads anymore.
And FYI for the ones you didn't mention...
5.3 truck heads (casting #862 and 706) are also a very popular base casting for porting/modifying, due to their even smaller (61.15cc) chamber size which raises compression when used on a LS1/6 engine..
6.0 truck heads (casting #317) are popular heads with the forced induction crowd, as they are basically the same as 243 heads, but with larger 71.06cc chamber size, which lowers compression when used on a LS1/6 engine.
Race Director
Joined: Jan 2000
Posts: 12,375
Likes: 406
From: Florida
Good summary. Just one thing to add: the "LS6" head (243's from 02-04) feature a hollow-stem intake valve in addition to the sodium filled exhaust one. These are the lightest OEM valves you can get.
Also, if you mean an L92 or LS3 head (L76 is the intake piece that goes with the L92 head), this outflows the 243 by a substantial margin, not the other way around. We're talking 340cfm on the intake side vs 278 or so for a 243 casting. The L76 has huge ports: 240cc on the intake vs. 210 for the 243, and valves (2.125 in. vs 2.0). The L76 would probably kill low end torque on a 347cid engine.
Also, if you mean an L92 or LS3 head (L76 is the intake piece that goes with the L92 head), this outflows the 243 by a substantial margin, not the other way around. We're talking 340cfm on the intake side vs 278 or so for a 243 casting. The L76 has huge ports: 240cc on the intake vs. 210 for the 243, and valves (2.125 in. vs 2.0). The L76 would probably kill low end torque on a 347cid engine.
Last edited by TTRotary; Jul 17, 2007 at 11:37 PM.
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Also, if you mean an L92 or LS3 head (L76 is the intake piece that goes with the L92 head), this outflows the 243 by a substantial margin, not the other way around. We're talking 340cfm on the intake side vs 278 or so for a 243 casting. The L76 has huge ports: 240cc on the intake vs. 210 for the 243, and valves (2.125 in. vs 2.0). The L76 would probably kill low end torque on a 347cid engine.
YES that is it. I though I saw something on LS1Tech that even the volume of air was higher, the flow was not as quick and yes low end tq was killed with the L76 heads.
the 243 heads with lift no greater then .600 was still the best head.
Lift above .600 was moot as it did not increase air flow so no need to beat up the valve system with that high a lift.
Drifting
Joined: Oct 2004
Posts: 1,345
Likes: 3
From: Mesa Arizona
This is really good info
A friend and I were at a show last weekend. We saw a bunch of LS based engines with all of the above casting #'s. (except 241's and 853's)
I was curious about the differences.
Thanks guys!
A friend and I were at a show last weekend. We saw a bunch of LS based engines with all of the above casting #'s. (except 241's and 853's)
I was curious about the differences.
Thanks guys!
Le Mans Master
Joined: Jul 2004
Posts: 7,727
Likes: 7
From: Twilight zone
St. Jude Donor '05-'06
Often not mentioned or overlooked,are these heads(probably because it doesn't mean to much
),but this is what came off my 98 and it threw me for a while.
Nice to see someone mention them even if it is with a
),but this is what came off my 98 and it threw me for a while.Nice to see someone mention them even if it is with a
Racer
Joined: Jun 2007
Posts: 392
Likes: 1
From: TX
The 806 heads were also perimeter bolt castings as opposed to the '99-up, LS1 & LS6 heads (853, 241, 243's), which are centerbolt style heads...
Race Director
Joined: Oct 2002
Posts: 16,477
Likes: 26
From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
It's not that they were machined different. The difference is a small notch cast into the head, located below the #3/6 cylinders (circled below)
ALL of the 806 perimeter bolt castings had this notch.
SOME of the 853s, and SOME of the 862's had it
None of the others did. If the head doesn't have the notch, MLS gaskets are ok to use.
And FYI, I'm using Cometic MLS gaskets on 862 heads that do have the notch, no problems at all.
ALL of the 806 perimeter bolt castings had this notch.
SOME of the 853s, and SOME of the 862's had it
None of the others did. If the head doesn't have the notch, MLS gaskets are ok to use.
And FYI, I'm using Cometic MLS gaskets on 862 heads that do have the notch, no problems at all.
Safety Car
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From: Da U.P.
Melting Slicks
Joined: Mar 2009
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From: Odessa FL
St. Jude Donor '10-'12-'13-'14-'15-'16-'17