I'm getting a water leak from the head gasket area on one of my 226 engines and have determined that the head is not as flat as it needs to be. Does anyone know how many thousands of material can be removed from a previously untouched head before I run into issues such as valves hitting the head surface? I can't find a spec anywhere to give to my machinist to let him know the maximum that he can cut from it to true it up.

 

What I would do first, before talking to a machinist is install a new head gasket and then re torque the head to specifications and see if it still leaks. If the leak persists then consider getting the head shaved. I have heard of 60 thousands of an inch shaved off these heads but you probably won't have to go that high since yours is still factory.

 

Have you checked the head with a straight edge and feeler gage to see how warped it is?
I would think the automotive machinist would know the limits.

 

A little searching should reveal the procedure used to gain clearance for valves and pistons when a head has been surfaced. Modeling clay is placed in the head where the valves and the piston extend into the combustion chamber. The head is placed loosely on the block and the engine is turned over by hand. The imprint in the clay shows how much clearance you have to work with. The head is then relieved in areas where the contact would be. Checks are made until there is clearance in any area of potential contact. Finally, the head is torqued to specs and clearance checked. This is a slow procedure but is a must. Go here for a better explaination.

http://www.racingheadservice.com/rhs...learance-guide

 

Did you try re-torquing? On the V8's up to 50 - 60 thou can be milled if piston and valve clearances are checked, but that's for raising compression. I'd say the machinist can safely go 30 and he'll probably gasp when you tell him that.

 

I did check the head with a straight edge and it was obvious that the head especially on the edges (where the water jackets have a narrow sealing surface) was warped. The block surface on the other hand was very good. This engine had just been rebuilt and the leakage occurred on initial fill up. After removing the properly torqued head, it was seen that the head gasket sealant (copper gasket seal) had transferred nicely to the complete head surface with the exception of the outer water jacket area which had no transfer and leaked badly. Checked surfaces with the straight edge and warpage at that area was found. Being that my machinist is no flathead expert, I am not sure he will know how far he can cut it before I get in trouble. Thus my question . . .

 

Should be OK to .060" I just had a 226 head milled (needed almost all of the .060 to get it flat!). Haven't checks clearance but looking down the plug hole it's easily 3/16" from the bottom of the spark plug hole so don't think it will be an issue

Should also bump the compression on the 226 which is abhorrently low anyhow

BTW I guess setting up the head is a PITA, took my shop a while and I paid for the time, because it was a bit more than a normal

 

Thanks Ray. I wondered how to check this.

 

Thanks for the info. Always good to hear from someone else who has done exactly what I need to do. The head will be dropped off at the machine shop on Monday. Ill be in Tennessee the rest of the week (at the F100 Supernationals) and am hoping to pick it up when I get back. Let me know if you run into any issues and I'll do the same.