Milling 243 or 241 heads
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
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From: BFE
The 4-8/5.3 L truck head may be a better starting point. CC is 61 to start with. This appears to be the quickest/most economical way to make serious compression gains and maintain as much PTV clearance as possible.
These heads start life with the smaller intake valves. Re-fits to the larger valves looks easy.
I agree with the other posters .025-.030 appears to be a "safe" amount although others have run more seriously milled heads.
These heads start life with the smaller intake valves. Re-fits to the larger valves looks easy.
I agree with the other posters .025-.030 appears to be a "safe" amount although others have run more seriously milled heads.
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TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
What are you trying to achieve? Like what compression? For which purpose? ?What fuel will you be using?
Size of motor? That is the info we need to determine amount of mill. LS motors rarely use dome pistons unless in drag only full race applications.
If you are just shooting for a number, .040>.045 mill is maximum and on a non ported head this will mean reduced flow. Milling that much also limits the size of cam you can put in without flycutting OEM pistons or having valve reliefs.
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Hmmmm, OK.
What are you trying to achieve? Like what compression? For which purpose? ?What fuel will you be using?
Size of motor? That is the info we need to determine amount of mill. LS motors rarely use dome pistons unless in drag only full race applications.
If you are just shooting for a number, .040>.045 mill is maximum and on a non ported head this will mean reduced flow. Milling that much also limits the size of cam you can put in without flycutting OEM pistons or having valve reliefs.
What are you trying to achieve? Like what compression? For which purpose? ?What fuel will you be using?
Size of motor? That is the info we need to determine amount of mill. LS motors rarely use dome pistons unless in drag only full race applications.
If you are just shooting for a number, .040>.045 mill is maximum and on a non ported head this will mean reduced flow. Milling that much also limits the size of cam you can put in without flycutting OEM pistons or having valve reliefs.
"What is the maximum that can be milled from a 241 or 243 head before issues with deck thickness and reliabilty problems etc."
I am fully aware of all the things you mention and more that happen when any cylinder head is milled a large amount.
Thank you
Sorry maybe I should ask that question a different way,
"What is the maximum that can be milled from a 241 or 243 head before issues with deck thickness and reliabilty problems etc."
I am fully aware of all the things you mention and more that happen when any cylinder head is milled a large amount.
Thank you
"What is the maximum that can be milled from a 241 or 243 head before issues with deck thickness and reliabilty problems etc."
I am fully aware of all the things you mention and more that happen when any cylinder head is milled a large amount.
Thank you
one of the bigger issues with going over .030 is you really want to mill the intake face as well to keep the manifold lined up. We did a 5.3 set .050 on the deck, .030 on the intake face, and the victor jr lined up PERFECT with the bottom of the ports.
If you're considering the ls1 heads - definitely go with the 5.3 heads. However, the 243's are a better head overall, so if you can reach you compression goal with them, I'd go with the 243's.
I'll go and measure the deck thickness of the 243 heads I have.
EDIT: I am getting just over .400 thick from a coolant hole behind the squish pad. Its hard to get at, so I made some go-no-go thingie, and then measured when it went. Also, not all castings are going to be the same thickness everywhere.
If you're considering the ls1 heads - definitely go with the 5.3 heads. However, the 243's are a better head overall, so if you can reach you compression goal with them, I'd go with the 243's.
I'll go and measure the deck thickness of the 243 heads I have.
EDIT: I am getting just over .400 thick from a coolant hole behind the squish pad. Its hard to get at, so I made some go-no-go thingie, and then measured when it went. Also, not all castings are going to be the same thickness everywhere.
Last edited by The_Rizzle; Jan 4, 2011 at 10:59 AM.
