cylinder head warpage spec for mk2 idi na hydra

[FrankenDiesel]

As title states what's the spec that these heads have to be in before being considered warped?

Edit: just found it In the Bentley.

.004
However it says that me/mf heads cannot be refaced, yet I have read of people resurfacing these heads. Why is that?

[Dakotakid]

Whether or not you are able to insert 0.004 inch feeler gauge under that straightedge while holding in rather perfect.
Can do it at night with a dim to moderate flashlight underneath. What ever works.

However, it is a whole lot better if you can NOT insert that much. The face of the head has to be immaculately clean and absolutely carbon-free and you need to check it several different places NOT over the pre-cups.

You need to hold the head at an optimal mechanical advantage....while holding the straight AND the feeler gauges. A nice time to have 4 hands and one neurological system.

[burn_your_money]

The Bentley lies, you can resurface them. Just remove the precups before machining. I wouldn't run a head that is warped over 0.002" but that's just me. It's under $100 to get the head machined usually.

[fatmobile]

Surface it much and the cam will rock in it's journals,.. like a teeter tooter.

[theman53]

I have always wondered about the surface head argument. One could overheat the car and not drive it, pull the head right then, and surface it. Then the cam might be rocking in the bores. At another way is one overheats it, tries to fix it 10 ways, drives it several thousand miles, and then tries to pull it off and surface it. I would think by that time the cam has already worn into the miss shaped bores from being warped. .004" is not much but how many have plastigauged the cam? I know of a couple and even with the uneven wear they still were in spec. Just a thought.

[libbydiesel]

I think the spec is that if you chop of one head, two grow back.

[Dakotakid]

I believe the "wear-in" philosophy would tend to result in a broken camshaft as it would be under tension. Tell you what, let's put one on that old blue stinky car and see who is right! Game? We can set up a little "office pool" with mileage guesses.

Man, THAT sounds like fun.

[theman53]

I believe the "wear-in" philosophy would tend to result in a broken camshaft as it would be under tension. Tell you what, let's put one on that old blue stinky car and see who is right! Game? We can set up a little "office pool" with mileage guesses.

Man, THAT sounds like fun.

That is a possibility. I think for .004-.010 it wouldn't, but maybe. Then again I bet the cam is tougher than the aluminum. Either way you have a problem.

[air-cooled or diesel]

when you resurface a head the valves will sit lower in chamber, if now you set valves back in some the cam will open valves farther, now you straighten cam bores and cam opens valves a little further. if now somehow you can economically adjust for this the head might work.

[vanbcguy]

when you resurface a head the valves will sit lower in chamber, if now you set valves back in some the cam will open valves farther, now you straighten cam bores and cam opens valves a little further. if now somehow you can economically adjust for this the head might work.

Don't forget you've got hydraulic lifters compensating for any difference in distance between the cam and the valve... So that actually isn't how it works.  The lifter adjusts itself to the clearance between the cam on its base circle and a closed valve maintaining the same amount of movement regardless of other changes.  That's why reground cams with a smaller base circle provide more lift despite the 'lift' portion of the cam being in exactly the same place with respect to the centerline of the cam.