How much can be safely milled of 243 or 241 heads?

Standard chambers are around 66 cc I believe.

How small can the combustion chambers be made?

 

the 243 is 64.43cc ive seen ppl go 0.030 on them.

 

I recently saw a thread about some one milling their heads .70 .

 

^Yeah that was nuts, i see most go around .025".

 

What are you trying to achieve?

 

Reduced chamber volume ............ More compression... without to much dome

 

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.

 

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.

 

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

 

I think anything over .045" is getting pretty aggressive. These stock castings are not that thick and with that amount of milling I would be worried about sealing issues on a heavy power adder car. I have seen people mill more then that but I did not get to see how thick the deck was.

 

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.

 

What cam are you guys running that have 243's milled .030?

 

I'm running 59cc's with a MS4 cam but my pistons have -2cc valve reliefs.

 

I'm sorry should have said 241's.

 

How much would need to be milled to go from 64cc's to 62cc's? That's what mine are.

 

.012"