milling question
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Joined: Apr 2002
Posts: 780
milling question
what is the maximum you can mill LT1 heads without having to mill the block as well? is it common to mill the block? if the heads are milled a lot, and the block isnt milled, is there a gasket that can work as an adapter?
thanks
thanks
Registered User
Joined: Aug 2002
Posts: 1,509
From: Red Oak Texas
Most people mill the heads .003-.010 (or what ever it takes to clean them up and make em flat). I really do not see a problem with milling them .030 or so as long as you do not cut into the hardened seat. The only bad thing is if they ever need surfacing again you are making the deck thinner and thinner so it is easier to warp. I have people mill .030 and not have a problem but you are just limiting the # of times that they can be milled in the future.
If you have a stock bottom end the pistons are down in the hole about .030-.035 and that is ALOT to remove from the top of the block. Most aftermarket pistons have the wrist pin in a diff. location that raises the piston in the bore so you may need to take off very little to get the piston at "zero deck". If you have stock pistons and you want to get the quench better (and raise compression) than use a thinner head gasket. No matter how much you mill the heads the pistons will still be .030-.035 in the hole, after you figure in a stock LT1 head gasket (.051) the piston is .085 or so away from the deck. An Impala head gasket (.029)will move the piston closer to the deck and increase compression and have a better quench (.060 or so). You would like it to be .035-.040 but unless you cahnge pistons or deck the block you will not see that.
Milling the head removes cc's from the chamber only and a thinner head gasket removes cc's from the entire bore dia. so milling .020 is removing about the same cc's as a .012 reduction in head gasket thickness.
If you do this and still want MORE compression than milling the heads or changing pistons would be the next step. If you use thinner head gaskets AND mill .030 or so than you "MIGHT" need to make the intake bolt holes a lil longer or mill the intake side of the head or intake so things line up correctly.
NightTrain66
If you have a stock bottom end the pistons are down in the hole about .030-.035 and that is ALOT to remove from the top of the block. Most aftermarket pistons have the wrist pin in a diff. location that raises the piston in the bore so you may need to take off very little to get the piston at "zero deck". If you have stock pistons and you want to get the quench better (and raise compression) than use a thinner head gasket. No matter how much you mill the heads the pistons will still be .030-.035 in the hole, after you figure in a stock LT1 head gasket (.051) the piston is .085 or so away from the deck. An Impala head gasket (.029)will move the piston closer to the deck and increase compression and have a better quench (.060 or so). You would like it to be .035-.040 but unless you cahnge pistons or deck the block you will not see that.
Milling the head removes cc's from the chamber only and a thinner head gasket removes cc's from the entire bore dia. so milling .020 is removing about the same cc's as a .012 reduction in head gasket thickness.
If you do this and still want MORE compression than milling the heads or changing pistons would be the next step. If you use thinner head gaskets AND mill .030 or so than you "MIGHT" need to make the intake bolt holes a lil longer or mill the intake side of the head or intake so things line up correctly.
NightTrain66
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