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Dudes......The gasket manufacturer has specs on the RA finish for that paticular gasket. In my shop, or any shop Ive seen, alloys don't fare well with abrasives. they tend to be sticky, so surface finish is completed with the tooling, HSS usually.
 

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Here are the exact quotes:

Might try a FINE scotchbrite pad attached to a flat piece of wood and sprinkled liberally with diesel fuel. Go lightly and don't push unevenly or on hard to get spots. Just a light touch............
The OP simply wants to remove the "embossing" and some small particles of head gasket residue. When scraping with a plastic putty knife, it often won't remove the gasket and it definitely won't remove the embossing. Going to a metal bladed putty knife "may" take the gasket off, but often it can lead to small gouges in the heads surface when the gasket is stubborn. It also will NOT do anything about the embossing. If someone uses an abrasive paper or a scotchbrite, it MUST be backed by some flat surface.............just like not using you fingers to push on sandpaper when doing bodywork. This is a standard machine shop process for flattening parts that have an imperfection that prevents the part from laying flat.
Have you ever seen a granite inspection table calibrated and dressed? I'll guarantee that the flatness requirement is far greater than any car head needs. They use optical equipment and they buff the surface with an abrasive compound to remove irregularities. In the surface grinding area, parts are held to a magnetic table for "flat" surface grinding. Aluminum parts are secured by placing steel around the perimeter and using the magnet. These parts have to have a flat surface so the magnets can hold them tight to the surface. How do machinists correct parts that don't lay flat? They rub them on a piece of emery paper attached to a flat surface.

Where did you get that? Sanding with a scotchbrite pad simply destroys the flatness.
No it does not. The key is to back the abrasive with a flat supporting device.

But by telling someone to use a scotchbrite pad, you not only take a chance on his destroying the flatness of his aluminum head - you imply that is a good way to clean off gaskets.
I implied that it is a good way to clean off the embossing if desired, and small particles of a remaining head gasket will also wear off. Ever heard of anyone putting a gouge in a head by rubbing it on a FLAT abrasive surface? Look on Utube and you will find numerous videos where people are "resurfacing" and "flattening" head surfaces with various forms of abrasives. You also keep talking about how much metal will be removed. I miked a crankshaft journal before and after polishing it with my homebuilt polisher. It turned out beautiful and I only showed .0001 (1 ten thousandth) difference in the mic reading. Took only about a minute with a 1000 grit belt. The amount of material that gets removed from the head will be so minimal it will not affect flatness. Why don't you try putting a scotchbrite on a flat surface and rubbing it for a while. Mic it before and after........



Yes, and my engine was completely disassembled and washed by the machine shop to remove all abrasives and residual bearing material.
So basically you relied on the machine shop to do any cleaning? You didn't get into the engine and run brushes thru the galleys and swap out any residue yourself? Yet you are an expert on how to do machine processes.

Now here is a video that shows you that it doesn't destroy heads and that professionals do it.

If you care to see how flat a professional can lap something, here is another video.

The simple conclusion to be drawn from all of this is that lapping is how to make a part very flat, and it does not remove a lot of material in the process.
 

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Dudes......The gasket manufacturer has specs on the RA finish for that paticular gasket. In my shop, or any shop Ive seen, alloys don't fare well with abrasives. they tend to be sticky, so surface finish is completed with the tooling, HSS usually.
Yes, but he is not at a machine shop. He is working at home and he doesn't want to resurface his head which has become embossed and has some corrosion areas. He is looking for something he can do at home.

All cutting methods produce an RA finish . It doesn't matter whether its done with abrasive or with a steel tooth on a flycutter. The RA finish is simply a measurable standard of how high the peaks and valleys are, and how far apart they are. The shape of the roughness does not have to be circular as a flycutter produces. Very few automotive machine shops have the necessary measuring equipment to check the RA finish of the parts they machine, and other than high end machine shops, none of them check the parts they machine for each customer. If they have any means of verification, it is usually a simple comparison example where you hold it near a part and see if they look similar. The RA finish on a ground part such as a crankshaft is generally accepted on the basis of how it looks and the fact that they are using a known abrasive wheel and set up that produces acceptable parts.......and the consumer has no way to verify it either. I have machined parts on cylindrical grinding machines that had a specific RA finish requirement. As each part was removed from the machine, it was placed on a table and I used a guage that drug a probe across the finish to verify the RA finish. I have never seen one in an automotive machine shop.
The ground surface of a crank journal has microscopic teeth even though it appears smooth to the touch and visually. Thats why further polishing with a belt can smooth the journal to an even better RA finish. The belt is turned in the opposite direction that the grinding wheel was applied just so it takes the tooth off the journal. It certainly doesn't create out of roundness or peaks and valleys any more than using abrasive on a head surface would.......as long as its supported as demonstrated in the videos.

We have all used pedestal grinders to knock welds or protrusions off of parts. The finish produce by this rough grinding is very coarse. This same type of wheel can be used in a precision grinding situation and produce a very fine finish. How you use any abrasive is going to affect the outcome of the finished part. If someone has a head that needs minor resurfacing, and he doesn't have his own milling machine at home, what procedure should he use to clean up the head at home? The obvious answer is that finishing it with some type of abrasive is a good way. Applying lubricant of some type will prevent the stickyness you mentioned. You can't remachine a head every time you remove it. You can change/control the RA finish produced with abrasive by simply changing the grade of the abrasive being used. If someone has gotten the imprinting/corrosion/gasket residue removed from a part and feels the part is too smooth, simply using a somewhat coarser grade and a few minutes of lapping will correct the desired RA finish. It will not remove a lot of material unless that is the goal and very coarse paper and a LOT of lapping is used. There are people who acyually do it with the intent of flattening a surface that is bowed.


Now I have tried to be objective and provide good information based on my experience and provided video support as well as explanations of why abrasive resurfacing does work well. I haven't resorted to personal comments as I feel they say more about the person writing them than the person they are directed at. What I have provided is based on actual personal experience as well as the videos of others experience. Those that choose to learn something from this thread should search further and then make up their minds whether they think its problematic or not. Those that disagree with my assessment of what works are welcome to keep disagreeing.
 

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Here are the exact quotes:



The OP simply wants to remove the "embossing" and some small particles of head gasket residue. When scraping with a plastic putty knife, it often won't remove the gasket and it definitely won't remove the embossing. Going to a metal bladed putty knife "may" take the gasket off, but often it can lead to small gouges in the heads surface when the gasket is stubborn. It also will NOT do anything about the embossing. If someone uses an abrasive paper or a scotchbrite, it MUST be backed by some flat surface.............just like not using you fingers to push on sandpaper when doing bodywork. This is a standard machine shop process for flattening parts that have an imperfection that prevents the part from laying flat.
Have you ever seen a granite inspection table calibrated and dressed? I'll guarantee that the flatness requirement is far greater than any car head needs. They use optical equipment and they buff the surface with an abrasive compound to remove irregularities. In the surface grinding area, parts are held to a magnetic table for "flat" surface grinding. Aluminum parts are secured by placing steel around the perimeter and using the magnet. These parts have to have a flat surface so the magnets can hold them tight to the surface. How do machinists correct parts that don't lay flat? They rub them on a piece of emery paper attached to a flat surface.



No it does not. The key is to back the abrasive with a flat supporting device.



I implied that it is a good way to clean off the embossing if desired, and small particles of a remaining head gasket will also wear off. Ever heard of anyone putting a gouge in a head by rubbing it on a FLAT abrasive surface? Look on Utube and you will find numerous videos where people are "resurfacing" and "flattening" head surfaces with various forms of abrasives. You also keep talking about how much metal will be removed. I miked a crankshaft journal before and after polishing it with my homebuilt polisher. It turned out beautiful and I only showed .0001 (1 ten thousandth) difference in the mic reading. Took only about a minute with a 1000 grit belt. The amount of material that gets removed from the head will be so minimal it will not affect flatness. Why don't you try putting a scotchbrite on a flat surface and rubbing it for a while. Mic it before and after........





So basically you relied on the machine shop to do any cleaning? You didn't get into the engine and run brushes thru the galleys and swap out any residue yourself? Yet you are an expert on how to do machine processes.

Now here is a video that shows you that it doesn't destroy heads and that professionals do it.

If you care to see how flat a professional can lap something, here is another video.

The simple conclusion to be drawn from all of this is that lapping is how to make a part very flat, and it does not remove a lot of material in the process.
Lapping anything with a scotch brite pad does not make it flat. And that has always been the issue here.

You argue like my sister. Im done.

Sent from my moto g power using Tapatalk
 

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For those of you who want good information on the types of head gaskets available and the best RA finishes for each type of gasket, watch this 10 minute Summit Racing video below. You will notice that he actually has a "profilometer" for checking the surfaces, and that there is a wide variation on acceptable RA finish/gasket used. Its not one RA fits all.
 

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I pulled an old set of LS Chevy heads down off a shelf and spent a few minutes working on them with a "Scotchbrite" pad. It occurred to me that some may have thought I was talking about the round Scotchbrite pads. I'm not. I agree, don't use those on heads. The rectangular pads are the ones I use. Here are some comparison pictures of a pair of heads from the same engine. . You can see that the prepped head is a big improvement over the unprepped head. Its not ruined and minimal material was removed. The head is as flat as it was before I started. Absolutely no problem and minimal investment in time and material. Edit add: One thing I should have said is that I used a piece of flat MDF (seen in the last picture) to push the scotchbrite accross the head applying even pressure. I did NOT just rub the Scotchbrite against the head with my hand. Some people use different things to do it. As long as it pretty flat it should work fine. The WD40 is the key to making it work smoothly.
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I always wondered on how and what folks did if they had to do a head swap with the engine still in the vehicle and how to have the block and cylinder head prepped and cleaned. Some good videos and information here.
 

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I say NO to a whiz wheel and scotch brite pads. All I use is a large flat file, go 45 degrees one way, and 45 degrees the other way until there is no drag on the file. Let the file do the work, it should take a couple of passes, clean with lacquer thinner and a clean cloth or those blue paper towels. I have a large Bluepoint flat file I use for jobs like this. Or on engine block surfaces.
 
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