How to Resurface a Cylinder Head at Home

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In order for a cylinder head to work properly, it needs to have a near perfectly flat surface to seal against the head gasket. In this video, we show how we machined our cylinder head at home, with a flat surface, a piece of sandpaper and some light pressure. The result has proven to work, as the engine is still to this day operating fine.

The "proper" way to machine a cylinder head is by having a machine shop do it on a surface grinder. However, these problems often pop up when you least expect it. Maybe you need to get the car back on the road asap. Maybe you cant afford to have it done the 'proper' way. Whatever the case, this basic DIY repair job is do-able in your own home with basic tools you probably already own.

This may or may not work properly for your circumstance, depending on how bad the cylinder head is to start with, as well as the engine block surface. Many metal style gaskets will require a near mirror finish to seal, which must be achieved by a machine. However, this repair may get you out of trouble for a short time.

*dislaimer* - Only work on your own vehicle if you are allowed to in your region/country/state/town. Otherwise, make sure this job is carried out by a licenced mechanic.

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Good, basic introduction to lapping a cylinder head.
Great thread of useful comments.
This is certainly doable, however you have to have a good idea of how to measure the different types of warps.
If I had to do this manually, like this I would try to set things up so I was wet-sanding it in effect. This would mean forgoing a flat horizontal set-up to something akin to a ramp. It would ~1.5x length of the head, and the top edge would have some soaker hose or garden hose with 50 pinholes in it attached to my spigot to allow water to flow over the wet sandpaper while stroking the head to remove grit and metal swarf.
Additionally, I'd take a permanent magic marker and crosshatch the face of the head so I could occasionally stop and see where/how the head was scrapping in.
Might have to reapply a few times.
I'd also start at 200/400 especially for aluminum unless it was warped significantly.
And, don't even start doing any of this until that head has had all gasket/rtv/etc scrapped off. Use a razor blade, solvent, whatever to get that 100% clean before starting else you're going to end up having to scrape even more and take more material off, lowering your deck height.
You also have to know how much you can scrape off before it either start affecting compression or maybe valve height.
I'm assuming a decent machine shop is ~$100 to do this, however if much more then it might actually be worth the sweat equity.

boots

I’ve never done this before but I do work at a machine shop and there’s a couple things I’d do differently.
First of all I’d get a larger piece strip of sandpaper and wet sand with machining oil.
Start at a higher grit that 100.
You’re likely working with aluminum and even 400 grit can get out of hand pretty quickly.
Invest in some different grits, keep it clean, and above all else take your time.

johanneslebrecht

Looks like you need a larger sanding area so the ends of the head doesn't ever leave the sand center of the head is getting sanded down more than the 4-5 inches of the ends. Idk.

LJC

You have a big problem with your method that can be easily solved. If you watch your sanding process, you'll note that the end of the head overlaps the sandpaper each time you stoke to the left and back. At the same time, the center of the head strokes somewhat to the edge and then back, without overlapping the end. What this causes is the center of the head experiences more contact time with the sandpaper than the ends, and thus, you will sand a hollow on the center portions of the head. And you'll do it pretty quickly. The solution is to construct a larger sanding surface that will allow the entire surface of the head to be in contact with sandpaper at all times. As well, your glass substrate is actually quite flexible, so whatever you're using to support the glass should in itself, be very rigid and flat - a very large granite flat would work just fine. This will eliminate preferential material removal from the center.
The process you're using is actually that used by amateur telescope makers to grind concave mirrors. With glass, the process is much slower and the amount of material is considerably less, with the same result.

hughezzell

I have done two alloy heads using this method on laminated glass with the spray bostik adhesive trick like you used. But I used 220-240 paper with running water from hose, it cuts plenty fast enough. After a few minutes work the 220-240 has lost its sharpness and is like a 400 so you have already got a nice final finish without changing papers :)

michaely

I’ve used this recut before different setup but dykem dye or even market to see your true end results ensures you have no low spots or visible bows or other issues. But still thumbs up
For teaching the youngins creativity

Musclecarrevivals

I hand lapped my head and block together with grinding paste, does an even better job as both surfaces are flat to each other. Can only do that if the engine is out and you clean the entire head and block after though

Xempt_One

Straight lines are the worst thing you can do. Also, no lubrication or cutting oil to clear the shavings. Iron heads are different than aluminum of course, but they still need confusion on the milling marks to seat. Smooth isn't the key. The gasket needs something to bite into. I use 220 for first cut and 320 for final and work in figure eight motion. I have a video posted as well.

jimkruse

That might work with a light head, but with a heavier one you might want to stick the sandpaper sheets to a large flat plank and also stick a 10 pounds weight on top for uniformity while you just do the back and forth movement (without applying any more downward pressure).

soupflood

I like the look of this method, though if I were to try that with my International 345 I’d give meself a hernia…
I could probably adhesive some grip handles on the sheet and use it like a block plane though. Might give that a go.

Beuwen_The_Dragon

Yes this actually works., yes many people have done it exactly like this for many years with much success. Not everyone has an automotive machine shop around the corner.

briana

I picked up some thick laminated glass stereo / shelf panes. I picked the smallest for my motorcycle head needs. Coffee table & dining table glass is great too. Yes a finer grade of wetable sand paper huh.

pauloconnor

I always know I’m in for a good time when the video starts “This is probably the most dodgiest way you can do this at home…”

You sold me. I’m in. 🤘🏻😎🤘🏻

BlackwaterDSM