If I have a good running LT1, 73000 miles and just removing the heads for some porting, cleaning and valve lapping is it absolutely necessary to have the heads milled? The engine has never been overheated and I've checked them with a straight edge. So is taking off .003-.005 of material really necessary? I worked in a shop years ago and watched people do the old Chrysler four banger head gasket swap in about an hour and the cars never came back. They never had the heads milled. I know it's not totally apples to apples comparison.

 

Why not have about .020 taken off and use the Impy gaskets? It will help the performance, especially since you have a cam, as in bleeds off compression.

 

If they are flat side to side and back to front (with a tolerance of 0.002-0.003") than there is no reason to have them surfaced.

Rich

 

I agree with you Z, but right now I just wanted to add a few more ponies to the mix without too much work to the heads. I didn't want to have them milled now and again In about two years when I have the engine completely rebuilt and heads sent to AI or LE to be fully done.

 

have a machine shop check the deck on them, then there's no question as to the state of the mating surface

 

You can only remove .01 from the LT1 heads. Ill be doing this along with the thinner impala head gaskets to get a cheap bump in compression.

 

What happens it they're milled further, and how do you know this?

 

That is not correct. Mine have been miled .010 when done by Lloyd about 5 years ago. When they go back to him for some more work he wants to cut them another .020. I asked about this, as far as how much is too much, and he said they could be milled one more time after that.

 

If that is the case, my heads will not be lasting long mine are milled .05, I highly doubt this is true.

 

Rich, (rskrause) just wanted to thank you for your help, of course everyone else that responded as well, but Rich always seem to be there everytime with the answer I'm looking for. Once again thanks.

 

You are very welcome! Happy motoring

Rich

 

I re-used heads from a 167,000 mile motor with no milling.

 

If you are going to pull the heads, it makes sense to measure and mill if necessary (straight edge not precise enough). You may want to take the opportunity to check your block deck as well. When I did my 383 block, the decks were not true. We decked the block enough to get, in combination with the piston height and head gasket thickness, the proper quench.

 

With a standard composite gasket, if the surface is straight to .003" across the length of the head and you cannot feel any imperfections in the fire ring area with your fingernail you can skip the surface. Just think about what you are trying to accomplish - sealing thousands of pounds of compression gasses with a .125" wide steel ring, if there is any indenting of the aluminum, or scratches you may run into sealing issues.