Machining a cylinder head

Walltoddj · Jan 3, 2014

The key was to have some very slight cutting marks so the surface is not perfectly smooth. I have heard (cannot prove and don't have any info on it) that perfectly smooth surfaces for heads fail due to lack of grip.

You are right the key is not a smooth surface at General Motor this is what we did on our heads and yes was to give it grip.

Todd

BaronJ · Jan 3, 2014

Hi Guys,

Following this thread with interest ! But I have a question. If the head is warped, then what do you use as the reference face when setting up ?

Walltoddj · Jan 3, 2014

BaronJ said:
Hi Guys,

Following this thread with interest ! But I have a question. If the head is warped, then what do you use as the reference face when setting up ?

When we made the cyl heads we used 4 points on the mate face of the head, then had post come in from the back to clamp to for machining the face. This was done last due to all the machining, pressing in the guides, and pressing in the seats with causes the head to twist and bend. If I remember we pressed at about 1500 psi on a 2" ram if was not supported correctly we could break aluminum heads.
Todd

Hopper · Jan 3, 2014

Many a head resurfaced on a milling machine here in the remote colonies where grinders are scarce.
When machining old/warped heads, be sure to shim any gaps between the other surface of the head and the mill table before pulling down the clamping bolts. Otherwise the clamping bolts will pull the head out of shape and when you release them after machining your nice flat surface, it will spring back into a warp again.

Krutch · Jan 5, 2014

Krutch said:
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I do Harley heads. I only clean up the head surface for warpage and pulled inserts. Taking as little as I can get away with. I also engrave the amount taken off into the head next to the gasket surface so the next guy knows how much has been removed.

Seeing as how I didn't add it at the time I posted my thread and reading others comments about gasket surface condition, I should say that after I "make new" said surface I bead blast same to rough it for gasket crush. I have yet to do any CI heads as the only one I'm likely to work on would be Knuckle heads. About as rare as hens' teeth anymore.