Quote:
Originally Posted by philcobill
I am not sure how to figure out the RA finish. Is there is a way to measure it?
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Yes Bill, there is a machine that we use for this. It is called an Optical Profilometer.
Maybe I should not have engaged in this thread, but I did so because you said you wanted to do things correctly. What I am struggling with is "why" did the first head gasket fail to begin with? As Neil stated, you need to use a precision straight edge to verify the deck surface is indeed flat. That is generally the number one reason. Also, over-torquing the head nuts is another. Most hobbyists do not own a ground straight edge, and using a framing square or a carpenter's level is not the same.
Next, the head gasket you are proposing to use requires a very flat surface and a fine RA finish so it will seal. That is why I asked if you had someone who was knowledgeable (a true engine machinist and not just a hobbyist) who had actually inspected your engine block to recommend using that gasket. There are Pros & Cons for using it or not. That particular gasket is a modern gasket that has expectations that the deck surfaces must be extremely flat and very smooth as the core does not conform like a core-filled copper gasket does. The benefit of this gasket is it does not 'move' like a copper gasket, so it does not need re-torquings like a copper gasket would. Matter of fact, retorquing this gasket is not recommended by the manufacturer. The other thing this gasket does not like is scratches that can potentially be caused by using scuffing pads and wire wheels. Most people do not realize that a scuffing pad actually can remove cast iron fairly easily because it is a soft metal. If I have an engine block mounted into my Block Resurfacer where I can use a dial indicator to sweep the block across the entire plane, I can show you how there will be numerous valleys created where the scuffing pad took off a little more in certain areas and created a divot or a void. Most of the time these will only be 0.002"-0.003" (a typical human hair thickness is about 0.002") deep, however that number is greater than what that gasket can seal.
I could go on, but I will step aside and let others guide you as to what they feel is the proper method for you to proceed.