Mill jigs for decking heads

[frankendat]

So, I had a thought (which is scary in itself) Since I have a mill, what is needed to deck my heads? Is it just a matter of improvising a jig or are there specialized elements only found in specialized machines? I would figure the same rationale could be applied to decking the block, but I doubt my back is up to wrestling the block and setting it on the mill table, jig or no jig. Also, the block would surely tip the mill over on top of me....but the heads seem feasible. With the cost of cutters and such, boring the block, unless I wanted to go into the block boring business, seems cheaper to farm out (and the block wrestling problem, presents again.)

What am I missing?

[datzenmike]

I love doing my own 'stuff' but a huge outlay for a one time uses kind of dampens my enthusiasm. Got to be cheaper to send it out.

 

As for a head I got a thick glass stereo cabinet front door and well supported it on a table. Spray adhesive and sheets of 180 and 220 grit emery paper onto the glass, set the head on it (without the cam so the valves are closed) and using the sprocket hole for a grip pull and pushed it back and forth. Every 20 passes remove head and brush away the dust or it will act as ball bearings. Only the high spots are removed and it goes fast at first but as you get closer to flat there is more material to remove. Every 20 passes I would switch table ends and grip the rear of the head.

 

 

Head without cam is around 40 pounds? or under 50? It pushes down onto the sand paper pretty well. Just push and pull, don't press down.

 

 

 

 

 

Eventually only the high spot between 2 and 3 was left....

 

 

 

 

When near done I switched to 220 grit. Glass was free and the sand paper about $5. Time about 45 min.

 

Originally it would take a 0.015" feeler gauge between 2 and 3. This is about 3 times the allowable unevenness limit. When done I used an industrial straight edge and could not get a 0.002" feeler under it. This was a 'throw away' head for an LZ24 project I have so if the end cylinders have higher compression, I don't care. Most heads will have much less warp than this. Yes the cam did spin easily so it was more of a pucker than a warp. 

[frankendat]

An effective and budget minded solution--I love it! The new valves I purchased for the Z24 head do not present the same disparity in size (comparing intake and exhaust valve circumference) What valve sizes are in your pictured Nissan head?

[datzenmike]

The Z series valves are just a hair longer than L series. The head pictured is a U67 so

 

Intake...... 42mm.... 1.65"

Exhaust... 35mm.... 1.38"

[frankendat]

The valves arrived in individual marked bags, 13201-N8500 intake and 13202-N8500 exhaust. The intake valve face measured like yours, 1.65", but the exhaust valve face measured 1.50". (38mm) I checked the 4 exhaust valves and they were all 1.50.

 

The bigger exhaust valve face must make the size disparity, on mine, less pronounced. In your photos, the intake valve appears to have a much larger circumference, compared to the exhaust.

 

Thank you for responding

post script:: I used the terms intake and exhaust, based on your post. The larger valve face being "intake" and the smaller valve face "exhaust.

 

[datzenmike]

Did not know that but the L series exhausts were 1.38 and the Z series were 1.50". Always assumed they were the same.