milling down 6.0 heads

Im sure this has been beaten to death but it's hard to search with 3 letter words. I have a 5.3 im building up for my S10 I already have an LS6 cam, springs, and intake on it. But I also have a nice spare set of 317 6.0 heads laying around.They have nice big ports on them:luv: I know using them would make me lose power due to a loss in CR, but what if I had them milled like .040 and used them. Would that bring my CR back up to stock or a little higher and maybe see some decent gains due to the higher flow of the 317's?

I think the best way to go about it is to find the stock cc then have a shop mill them to that cc or a little smaller. might cost a little more, but I still havent found an exact number for milling my 243s yet and they are a more commen swap. there is a local shop that will mill my heads for 75 for the pair, and i'm going to see how much extra it will cost to have them do all the measurements and get my compression bumped to 10-10.5

the 317s are to big for the 5.3 IMO but you can mill .040 off of the 243s and that will put you at 10.2 to 1. I did that and i love it!

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Originally Posted by jake_03

the 317s are to big for the 5.3 IMO but you can mill .040 off of the 243s and that will put you at 10.2 to 1. I did that and i love it!

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I really don't wanna spend a bunch of $ on 243's right now. But are you saying the combustion chamber of the 317's will run over the smaller bore of the 5.3?

yep the 317's have larger combustible chambers u would have to use 243's or 241's to get those bigger valve ports

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Originally Posted by ChevyBeast05'

yep the 317's have larger combustible chambers u would have to use 243's or 241's to get those bigger valve ports

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Ok wow, that changes everything. There goes that idea. Oh well thanks anyway guys.

you should be able to sell those 317s and pick up a set of 241s for the same cost, but you could also just sell the 317s and get some mild porting done to your 5.3s

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Originally Posted by Lsx10

you should be able to sell those 317s and pick up a set of 241s for the same cost, but you could also just sell the 317s and get some mild porting done to your 5.3s

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Are 317's worth anything? What do they normally bring?

check on ls1tech, you can usually pick up 241s for 100-200 shipped and 317's go for around the same price, also depending on the mileage on your heads you may get a few bucks out of them.

does anyone know the difference between the 856(i think thats the numbers for 5.3 heads) and the 706 5.3 heads, which is more desired?

found this info on l92 heads dont know if it applies to all lsx heads or not but i thought i would share anyhow.

Milling Information for Combustion Chamber Sizing:
- Approximately 0.006” per 1-cc

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Originally Posted by banker099

found this info on l92 heads dont know if it applies to all lsx heads or not but i thought i would share anyhow.

Milling Information for Combustion Chamber Sizing:
- Approximately 0.006” per 1-cc

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that's pretty much universal. It does vary with bore size and how steepthe walls of the combustion chamber are, but 1cc per 6 thousanths is usually very close.