Difference between 241, 243 and 853 heads?? - CorvetteForum - Chevrolet Corvette Forum Discussion



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Difference between 241, 243 and 853 heads??

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Old 07-16-2007, 05:39 PM   #1
Corvette Don
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Default Difference between 241, 243 and 853 heads??

Whats the difference? I have 853's, which heads are good for porting and which flow the best? Thanks
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Old 07-16-2007, 08:03 PM   #2
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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.

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Old 07-16-2007, 10:09 PM   #3
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Great post!!!
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Old 07-16-2007, 10:13 PM   #4
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Nice writeup and explanation.
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Old 07-16-2007, 10:14 PM   #5
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Quote:
Originally Posted by Y2Kvert4me View Post
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.
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.
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Old 07-17-2007, 03:06 AM   #6
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'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...
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Old 07-17-2007, 07:23 AM   #7
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Cool stuff

I though I saw something that the new L76 heads dont flow as well as the 243 heads.
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Old 07-17-2007, 07:29 AM   #8
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Nice writeup and explanation.
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Old 07-17-2007, 10:24 PM   #9
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Thanks guys, so 853's are a sand cast head correct?
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Old 07-17-2007, 10:30 PM   #10
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Quote:
Originally Posted by Y2Kvert4me View Post
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.

Now that there's a well detailed answer. Thanks I learned a lot from this. Good stuff.
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Old 07-17-2007, 11:26 PM   #11
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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.

Last edited by TTRotary; 07-17-2007 at 11:37 PM.
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Old 07-18-2007, 07:26 AM   #12
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Quote:
Originally Posted by TTRotary View Post

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.
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Old 07-19-2007, 04:47 PM   #13
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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!
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Old 07-19-2007, 09:59 PM   #14
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Quote:
Originally Posted by JustLucky View Post

Also I belive 806 was the casting number on the '97-'98 LS1 heads...
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
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Old 07-22-2007, 04:05 AM   #15
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Quote:
Originally Posted by flynbya2 View Post
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

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...
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Old 07-22-2007, 02:31 PM   #16
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853 heads require the old style head gaskets, they are machined slightly different at the sealing surface.
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Old 07-22-2007, 03:15 PM   #17
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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.


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Old 07-16-2017, 11:15 PM   #18
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Old 07-17-2017, 10:41 AM   #19
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Quote:
Originally Posted by Corvette Don View Post
Thanks guys, so 853's are a sand cast head correct?
I was hoping someone would chime in here. I thought the biggest/only(?) difference between 241 and 853 was the casting method.
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Old 07-17-2017, 12:21 PM   #20
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Quote:
Originally Posted by Supercharged111 View Post
I was hoping someone would chime in here. I thought the biggest/only(?) difference between 241 and 853 was the casting method.
Someone might, but realize this is a 10 year old thread.
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