![]() If you’re not sure what kind of wood surface you’re working with, Hamm recommends looking at the grain of the wood: “If it repeats across the width of the grain, it’s veneer, because it’s been rotary-sliced off a single log to make a sheet.” Step 2: Clean your wood table Refinishing laminate won’t work-it’s plastic. Ra (µ in.Solid wood is a better candidate for refinishing than veneer, which tends to be thinner. General Surface Roughness guidelines BUT VERIFY WITH YOUR GASKET MAKER Going too smooth, or too rough can both cause problems with head gasket sealing for your application. Aluminum cylinder heads also often use a more modern head gasket choice that requires a specific surface roughness, or Ra. You might start with 80 – 100 grit for iron, while you may start with 120 or 150 grit for aluminum. Use a less aggressive grit for aluminum versus iron or steel. Grit choice also depends on gasket choice and head material. These tolerances might be more tight depending on your head gasket choice as well, and if you have a DOHC cylinder head design. The maximum allowable limit for out-of-flat sideways in any head is 0.002″ - with no sudden irregularities that exceed 0.001″ in any direction. On most pushrod engines with cast iron heads, up to 0.003″ out-of-flat lengthwise in V6 heads, 0.004″ for V8 heads, and up to 0.006″ for straight six cylinder heads is acceptable. The tolerance you are working to depends on your head’s material and gasket choice. Supported by a flat and even surface, such as a nice work bench or perhaps table saw surface etc.Wider than the width of the cylinder heads.You don’t want your head to move past an edge that might cause more aggressive wear. I used a glass shelf from a display cabinet, and as long as you are careful you shouldn’t damage it, but this is your call. You can buy a cheap sheet of glass from a local glass shop for about 20 dollars, and most cities do have a glass shop within 30 miles or so. This is why a THICK sheet of glass works well. If it’s not, your cylinder heads won’t be either and you will sand them unevenly. Regarding the surface, it must be 100% flat. If you don’t have feeler gauges for example, it’s time to buy some. Some of you may be thinking, but who has all of that laying around! The reality is that most people who do serious automotive work should have the majority of the above. A machinists straight edge, or make one (explained later). ![]() Headliner adhesive would make changing sandpaper very difficult. I used batting adhesive for sewing, since it’s designed to be washable. Grit selection depends on cylinder head material and head gasket selection. ![]()
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