How to resurface a head at home

[RunninWild]

Some of you know I've been having trouble getting my aaz head to run properly on my 1.6td. I can't deal with the amount of smoke I'm having on cold starts so I'm just going to put my old 1.6td head back on until I can get my aaz block rebuilt and get rid of this engine.

Now I don't have any measuring tools and after cleaning the head surface I could feel a low spot on one of the fire ring imprints on the head. Not wanting to spend much money getting this thing back together As I only need it to run 6 months or so I started playing on google to see if there was any home remedies.

I found this video of this old school guy who glued some sandpaper to a mirror and ran the head back and forth until it was flat. I figured I didn't have much to loose as the local machinist wants $180 to skim the head. $20 later and the Work begins.
Here is the video
https://youtu.be/mc_gaGAf2pk

I didnt take any before videos but here is where I'm at after about an hour. I also came up with the idea of running lines down the length of the head with a marker. This shows the progress you are making. As the lines disappear you are cutting back the high spots.

I'm using 120 grit paper and will probably finish it off with 150. As you can see the low spot I could feel was the least of my worries. The head has a pretty major warp but I'm confident I'll get it flat with another hour of work or so.

This probably isn't the proper way to skim your head but if you don't have much money and need something to get you by I don't see any problems with it. Remember to loosen or remove the cam before you attempt this.

[TylerDurden]

BTDT... a couple years ago.

I'd keep an eye on the level front to back. The precups are harder than the head and could tend to slant the job.


I used a fine wet/dry for finishing.

[libbydiesel]

I have done exactly that on several heads with excellent results.  I remove the pre-chamber inserts.  The head shown was very warped.  That's significantly worse than any I have sanded.

[RunninWild]

Yeah it's pretty bad but it's getting there. I'm probably 70% flat now.

[libbydiesel]

I use 120 grit paper from an 8" wide roll (floor sander paper).  That way you can use a single sheet large enough for the entire head without any seams.  Lubricate it well with WD-40 or the like.  It's also a good idea to change the angle of the head a little and move it a little on the paper so that irregularities in the paper get more evenly distributed. 

[RunninWild]

Good tips Libby! The local home hardware only had individual sheets. a roll on a large mirror or sheet of glass would have been much easier. I'm still waiting on parts in the mail so no rush to get this done. If I can get it flat by next a weekend I'll be happy. But realistically I'll probably finish it today.

How do you remove the precups? Just a punch in the injector hole? One of mine is turning out to have a fairly large crack. I wouldn't trust removing it and reinstalling it in its current state. Nor would I trust running it if I expected it to last long term.

[libbydiesel]

I use a wood dowel and hammer to remove the precups.  A hard punch will often damage the inner lip. 

[fatmobile]

 Sometimes setting a lifter adjusting shim on the prechamber face and smacking it can help loosen it up enough to pop it out from the injector side

[RunninWild]

Almost there! One trouble spot left. Hopefully knock it out tomorrow. ***ty it's in such a critical spot 😞

[Toby]

You guys are missing the most important thing in the last photo. You are sanding one of the heads of the exhaust valves. It should be well below the level of the head surface. Investigate why that is so before you go any further.

Are you checking the head for flatness with a machinist rule long enough to do the whole head at once? Shiny does not mean flat.

You are also laboring under a false assumption. "Warpage on an aluminum head is nothing to worry about. Low spots are a big problem if they are not caused by the warpage. If you torque down a warped aluminum head, it will straighten back out as you torque it down and as it is heat cycled a few times it will straighten back out. This won't work with a divit. I see some warping, but no divits in the pics, so you are probably wasting your time.

The other thing to consider, is that the cam bores are no longer straight if the head is warped. When you tighten it down the head will flatten out and the cam bores will come back into alignment. Once you surface it the cam bores will stay out of alignment when it is tightened down. If it is worn out junk, it won't matter, of course

[RunninWild]

There were a few divits I could feel with my fingers that have been flattened out so far. No I don't have a machinist straight edge. This is a last ditch effort to get the engine running better and I don't have any more money to throw into it. I know it's not proper and that shiny doesn't mean flat but how  the low Spots are reacting to sanding makes me believe it's flattening out. The videos I've watched of people using this method who are using a flat edge and checking for low Spots show that it does work. Maybe I went a little overboard but the last divit I could feel with my finger was just sanded out. I don't have much work left to get it completely "shiny" and I might as well finish at this point.

The valves are blow the surface. It looks like they are being sanded because of when I cleaned the surface before I began sanding.

[rallydiesel]

I'm looking forward to updates. The results look better than one cylinder head I had machined professionally. Considering these heads are officially not meant to resurfaced at all, I think you're doing a fine job!

[RunninWild]

Well this is as far as I'm going.

There's still a tiny spot that doesn't look even with the rest of the surface but all the sealing surfaces look good. Also it looks like a bit of a trail is forming between the precups which I'm betting is starting to cause the surface to be uneven so this is hopefully good enough. I'm going to install it this weekend if the weather cooperates. I'll let you guys know how it seals.

I'm also planning on reusing my mls head gasket. I know this isn't good practice but I've read on a few forums of people getting them to seal by drilling out the rivets cleaning all the surfaces and applying each layer with copper spray gasket. Most of the people that report doing this are on race engines that are torn apart and inspected on a regular basis. My gasket only has 100km on it so I doubt it would have any significant wear. I know gaskets work by being squished and conforming to provide a seal between the two surfaces So it will be interesting to see if it works!

[libbydiesel]

I think it looks good.  The unevenness from the harder pre-chambers is why I remove them.

[RunninWild]

Yeah ideally I would have removed them too but 3 of them Are cracked and I didnt want to risk breaking them or making them more likely to fall out after its installed.