Difference between 241 & 243 castings
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Burning Brakes
Joined: Dec 1999
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From: Richmond VA
Difference between 241 & 243 castings
SO what exactly are the differences between these two castings? Also, what type of flow numbers are you seeing using the stock castings with a good professional port and polish?
Thanks
Thanks
Tech Contributor
Joined: Mar 2003
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From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
243- 2001 and later Z06 heads have smaller combustion chambers than 241 castings which appear on all prior C5's. The smaller combustion chambers result in a .4 compression bump. The 243's also have a 3 angle valve job for improved flow.
On a 346 (5.7L) motor the 243 will give a 10.5:1 CR and the 241 will give a 10.1:1 CR. The 243 castings also have improved flow than the 241's for higher rpm performance and the 'D' shaped port on the exhaust side. All said the 243 tend to give a 15-20hp improvement over the 241's. Once ported the differences are not quite worth the money for the expensive 243 castings.
On a 346 (5.7L) motor the 243 will give a 10.5:1 CR and the 241 will give a 10.1:1 CR. The 243 castings also have improved flow than the 241's for higher rpm performance and the 'D' shaped port on the exhaust side. All said the 243 tend to give a 15-20hp improvement over the 241's. Once ported the differences are not quite worth the money for the expensive 243 castings.
Safety Car
Joined: Nov 2003
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From: San Diego, CA "leaf" "tee" "e"
Originally Posted by SpinMonster
243- 2001 and later Z06 heads have smaller combustion chambers than 241 castings which appear on all prior C5's.
Thread Starter
Burning Brakes
Joined: Dec 1999
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From: Richmond VA
Originally Posted by SpinMonster
Once ported the differences are not quite worth the money for the expensive 243 castings.
Eric
Le Mans Master
Joined: Apr 2001
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From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
Originally Posted by TrueBlueCoupe
So Does anyone have some flow numbers from ported GM heads? Or some recommendations on a good place to port them?
I figure some LS6 heads worked over by Phil at AI and a Futral cam will be a killer combo.
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Pro
Joined: Jul 2002
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Originally Posted by TrueBlueCoupe
So Does anyone have some flow numbers from ported GM heads? Or some recommendations on a good place to port them?
http://www.ls1tech.com/forums/showthread.php?t=317323
Melting Slicks
Joined: Mar 2003
Posts: 2,744
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From: FL
Cruise-In VI Veteran
There are a few different casting numbers on heads.. 853's are not perimeter bolt..
ALL the info you need right here
http://www.ls1tech.com/forums/showpo...2&postcount=41
Steve
ALL the info you need right here
http://www.ls1tech.com/forums/showpo...2&postcount=41
Steve
Safety Car
Joined: Oct 2000
Posts: 4,949
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From: Monticello MN
I've got a pair of stock 2000 C5 241 heads for sale, plus stock cam, injectors, intake, double-walled stainless exhaust manifolds, etc., all in great shape. I will have a set of 3.15 gears and stock converter for sale in a couple of months. A fair offer for any part, and it's yours. 
Ed
Ed
Tech Contributor
Joined: Mar 2003
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From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
You wont go wrong with TEA for the porting. The site lists some examples of the flow numbers and the low lift LS1's are impressive. The truck heads are the best bang for the buck even compared to AFR's.....with money left over.
Safety Car
Joined: Nov 2003
Posts: 4,979
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From: San Diego, CA "leaf" "tee" "e"
Originally Posted by Steve92LT1
There are a few different casting numbers on heads.. 853's are not perimeter bolt..
ALL the info you need right here
http://www.ls1tech.com/forums/showpo...2&postcount=41
Steve
ALL the info you need right here
http://www.ls1tech.com/forums/showpo...2&postcount=41
Steve
Racer
Joined: Sep 2002
Posts: 424
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From: Va, Beach VA
Originally Posted by TrueBlueCoupe
So Does anyone have some flow numbers from ported GM heads? Or some recommendations on a good place to port them?
Pro
Joined: Jul 2002
Posts: 525
Likes: 0
Originally Posted by TrueBlueCoupe
So Does anyone have some flow numbers from ported GM heads? Or some recommendations on a good place to port them?