243 head max mill
10-30-2010, 05:22 PM
#6
The only issue for me was manifold fitment, I cut off the plastic nubs and just used the brass ones to locate the manifold.
The 243 heads were ported by AI, went 10.60's N/A on my flycut but unassembled LS1 short GTO.
I am asking because if everything works out, I want to try to run NMCA Mean Street with the car next year. I must use unported LS6 heads, but can valve job any way I want, and can mill as much as I want.
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10-31-2010, 10:23 AM
#9
To the OP - if you need to mill the heads that far to get your compression where you want it, you need different pistons. What are you trying to build?
10-31-2010, 10:39 AM
#10
Not sure what you are getting at, but the distance between the piston and the head deck surface doesn't change with milling. Only milling the deck on the block, changing head gaskets, or changing compression height on the piston will change the quench.
To the OP - if you need to mill the heads that far to get your compression where you want it, you need different pistons. What are you trying to build?
To the OP - if you need to mill the heads that far to get your compression where you want it, you need different pistons. What are you trying to build?
. I forgot that the quench area of the head is milled right along with the rest of the head. Sorry lol
10-31-2010, 03:06 PM
#11
Not sure what you are getting at, but the distance between the piston and the head deck surface doesn't change with milling. Only milling the deck on the block, changing head gaskets, or changing compression height on the piston will change the quench.
To the OP - if you need to mill the heads that far to get your compression where you want it, you need different pistons. What are you trying to build?
To the OP - if you need to mill the heads that far to get your compression where you want it, you need different pistons. What are you trying to build?
10-31-2010, 05:10 PM
#12
I've got .050 (on 5.3 heads) done with no ill effects, however we did compensate the intake face to make up for the millling. At that point, the only issue you might run into is the intake bolt holes either need to be shifted, or oval the intake holes in the manifold. We took off .006 intake for every .010 deck. Intake manifold/port alignment was perfect with a victor jr where we could see the floor. Bolt holes were a little pushed up, but on the victor jr, the holes are big.
If the deck surface looks thick, and you're not taking off part of the valve seat, I can't see a problem with your .075, or more.
Using Johns rate of .006 per cc, you're down to 51 - 52cc's. How much smaller you want to go? This puts you at approx 13:1
Down to 47 ccs should take approx .030 more, and leave you with around 14:1, but I would definitely cc at stages before you do a full .100 mill, since the .006 per cc isn't completely accurate. the shallower the chamber, the more cc's you cut for the same amount removed. So a 317 head will lose more cc's for a .030 mill than a 243 head will.
You could try and work on your quench distance as well, since ally blocks expand more, even with the sleeves (although not as much as a all ally block) and tighten it up a little at a time. Just don't run it hard/high when cold!
Have you considered angle milling as well? its a good way to get more cc's milled away if you get close to the intake valve seats.
If the deck surface looks thick, and you're not taking off part of the valve seat, I can't see a problem with your .075, or more.
Using Johns rate of .006 per cc, you're down to 51 - 52cc's. How much smaller you want to go? This puts you at approx 13:1
Down to 47 ccs should take approx .030 more, and leave you with around 14:1, but I would definitely cc at stages before you do a full .100 mill, since the .006 per cc isn't completely accurate. the shallower the chamber, the more cc's you cut for the same amount removed. So a 317 head will lose more cc's for a .030 mill than a 243 head will.
You could try and work on your quench distance as well, since ally blocks expand more, even with the sleeves (although not as much as a all ally block) and tighten it up a little at a time. Just don't run it hard/high when cold!
Have you considered angle milling as well? its a good way to get more cc's milled away if you get close to the intake valve seats.
11-03-2010, 09:28 AM
#15
