Warped head cure.

[datzenmike]

I have a U67 head I recently removed from the engine I'm rebuilding. Short story... I used an industrial straight edge and there is 0.015" gap between 2 and 3. This is almost 4 times the allowable amount. There is a lesser amount between the outer two cylinders. The cam turns beautifully so I just want to level it. It will be on a Z24 block so the compression will be only slightly higher than normal.

 

So, I got a 2x2 foot 1 " board and glued a glass door from a stereo cabinet onto it with spray adhesive. (after checking the board was also level) Then glued 2 1/2 sheets of 80 grit end to end on one side and beside that, 2 1/2 sheets of 150 grit. I had to remove one of the rocker arms on the head to lower an exhaust valve and rotate the cam so none of the valves were in the way.

 

Placed the assembled head on the 80 grit and slid it forward and back, stopping every 5 to 10 times to blow away the aluminum dust or it will act like ball bearings and not remove more material. At first the very front by the timing chain and the very back of the head ground (not grinded!) away very fast, but as the ends lowered, more and more head was rubbing and this slowed down a lot and became work.

 

This head was put on the engine with copper coat dressing so it had to come off before it could be put on again anyway.

 

The center is higher than the left and right sides...

 

As more material comes off the left and right the center lowers

 

 

Eventually there is just the gap between the #2 and #3 cylinders that's low enough to be a concern...

 

 

Closer look...

 

 

Almost there... I tried to get a 0.002" feeler gauge to fit. It would almost, with a push but I would say less than .002"

 

 

More than good enough. Finished off with 150 grit

 

 

I would guess an hour of back and forth sanding. Couple of hundred passes, maybe?

Wear gloves. I was holding the cam sprocket.

Switch the head end for end. Blow away any aluminum dust as you see it and it will grind down faster.

Everything but the glass cost less than $20 and can be reused but for the sand paper which was $8.

I also got the materials, built it and had it done the same morning, no time spent driving to a machine shop twice to get it done there.

Did not have to remove the cam or cam towers or dismantle anything.

 

 

[tr8er]

Same method we use to grind glass.  Except we use an abrasive slurry on the glass.  This keeps the grounds washed away.  Skips sandpaper.  I expect it would work well for aluminum too, but not much beats the simplicity of your solution.  Thanks for the write up!   

[Draker]

The key is having a precision straight edge. 

 

Nice work.

[banzai510(hainz)]

We have a few at work. Machinist table is I guess another word for a straight Edge

[datzenmike]

 

It's used only for drafting and cutting plans.

 

Brushed stainless steel with beveled edge 36" x 3" by 1/8"

[hosestop@msn.com]

Loose cam towers ,how could they spin on

warped head ?

[datzenmike]

Well the head is over 4" thick top to bottom and has voids for coolant passages. Maybe the center between combustion chambers lifted upward or puckered from over heating???? I easily managed a 0.015" feeler gauge between 2 and 3. The pictures of the sanding down show the center much higher. The cam without the rockers on could be turned easily enough with one hand. Maybe the word warp should be high spot instead?

[az_rat210]

I did this on my A series head last year after I blew a head gasket.  But I used a thick piece of sheet metal and glued the sandpaper to it.  Then applied oil to the sandpaper to float away the dust, and used a figure 8 motion.

 

Head went back on with no leaks (after I had to repull it and clean out the bolt holes better).  Car has been running fine every since.

[datzenmike]

Here I thought I needed the services of a machine shop. I did mine dry and after half a dozen forward and backs the paper would be gray. I just leaned forward a blew it off. That's how I knew when.... when you could see the gray. 80 seemed about right, fast enough but didn't leave scores in the aluminum. I did have 150 ready but only made 5 or 6 good passes on it.

[wayno]

It is always good to chase the threads with a tap before putting the head back on, it doesn't hurt to clean the headbolts also.

[datzenmike]

Good idea. I power washed the block and specially the bolt holes. I'm going to use studs. This IS a Z24 and gasket problems seem to come with them. The holes are about 1.5 to 1.8" deep with threads starting about 1" down. Maybe the Z24 head bolts are too short?  Seems to me L20B threads start closer to the surface. Studs will allow me to snug all the way down to the last thread deep in the block and impossible to bottom out accidentally like a bolt.

[4perrev]

I've seen it done with a nice piece of tempered glass and abrasive compounds.  Works pretty good, but takes awhile.  We can't all afford a 7-15k milling machine!  Nice write up with pics.