NXcoupe
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Balanced and Blueprinted.
Now what does that mean? People throw around those terms all the time, few actually knowing what it means. Balancing is taking the pistons and making each one the same weight, down to the .1 of a gram. The rods are balanced using a jig to measure the large end and small end of the rod, so they are all the same at the end, again to a .1 of a gram or less depending on the balancer. Then the weight of the rings, the rod bearing, piston, pin, rod big and small end, are entered into the balancing bob weight calculation and then that weight is attached to each pair of rod journals and the crank is spun up. Then the machine will say where to drill holes into the crank to balance it. Kind of like balancing a tire, except you are usually removing weight rather than adding by drilling holes in the counterweights. Which is two fold, the crank gets lighter which is good, and the crank gets balanced which is also good.
Now, on to blueprinting. Blueprinting is the process of not only measuring all the clearances in an engine, but also assuring that every machining operation is performed properly and in spec. I have thousands of dollars worth of measuring equipment to verify what the block is correct and so are the rods before the engine is ever assembled. First the bore is checked at various points with a sunnen dial bore gauge, with a torque plate attached, and then checked at 90 degrees from the first set of measurements to verify the bore is round, not tapered, and in spec.
Next, each piston is measured, usually even before the engine block goes to the machine shop so we know what size the bore needs to be. We do this because depending on the end purpose of the engine, the clearances need to be adjusted. Say a nitrous shot of 300 needs more piston to wall clearance than an n/a engine does. All this is discussed with the customer before the first part is ordered, what the end use is going to be.
After all the pistons and bores are measured, each piston is given a letter, and each bore already has a number. Then each piston is taken and matched with the bores down to .0001" so that they average out to the target clearance. After that is finished, then we begin with the rod bearings by inserting them all into the rods after cleaning and then torque them to spec in a rod vise. Then the crank is cleaned, oil holes cleaned out, etc, and it is mic'd and all the diameters are written down, once again checked at 90 degree angles to confirm it is round. Then we set the dial bore gauge up to the diameter of the smallest journal, but usually we are only talking a few tenths of a thousandth, .0001.
Then the dial bore gauge is run into the rod bearing and the measurement it shows is your oil clearance. If the clearance is in spec, then that is written down and move on to the next, each rod has a letter as well, then once all clearances are written down, each rod is matched to a journal to give the best clearance in the target range. For instance, one rod is a bit on the high end of the clearance range, say .002 to .0025, so it's .0025, and we have a larger diameter rod journal, say 2.1235, we can put that rod on that journal, and it will net .002 clearance. follow me?
After that, all the main bearings are put in after the inside of the engine has been cleaned, and painted. Then the main caps are torqued onto the block. Next we set the dial bore gauge up with the appropriate crank main journal diameter and check each bearing for oil clearance. Main bearings can be moved around to net different clearances, but that usually doesn't work, but worth a try. The variance comes in the small differences in journal diameters in the block where the bearing sits. So what you have to do is get .001 under and .001 over, then mix and match until you get the clearances in spec. This also works for the rods too. I have to do this for just about every stroker engine I build because the cranks are on the top end of the range(bigger diamter) and will have no clearance when assembled.
So now you have all your rod journals done, main journals are done, and you can begin hand filing your rings. I use a manual grinder that holds the ring steady while it is ground and clearanced. go slow and steady, it's easy to make it too big. Set your ring gap spec from the sheet that comes from the manufacturer, what I set my gaps to for different applications is part of my business and I don't give them out. But you can use their recommendations and get it very close.
After that, then you put each piston measurement with each bore it best fits in and change the letter on it to the number of the cylinder, then you put the rod from that cylinder onto the piston for that cylinder, and so on. Then take the rings from each cylinder and put them on the piston for that cylinder as well. Then install crank, rod and piston assemblies and you have a blueprinted engine with all the spec's on it.
Now what does that mean? People throw around those terms all the time, few actually knowing what it means. Balancing is taking the pistons and making each one the same weight, down to the .1 of a gram. The rods are balanced using a jig to measure the large end and small end of the rod, so they are all the same at the end, again to a .1 of a gram or less depending on the balancer. Then the weight of the rings, the rod bearing, piston, pin, rod big and small end, are entered into the balancing bob weight calculation and then that weight is attached to each pair of rod journals and the crank is spun up. Then the machine will say where to drill holes into the crank to balance it. Kind of like balancing a tire, except you are usually removing weight rather than adding by drilling holes in the counterweights. Which is two fold, the crank gets lighter which is good, and the crank gets balanced which is also good.
Now, on to blueprinting. Blueprinting is the process of not only measuring all the clearances in an engine, but also assuring that every machining operation is performed properly and in spec. I have thousands of dollars worth of measuring equipment to verify what the block is correct and so are the rods before the engine is ever assembled. First the bore is checked at various points with a sunnen dial bore gauge, with a torque plate attached, and then checked at 90 degrees from the first set of measurements to verify the bore is round, not tapered, and in spec.
Next, each piston is measured, usually even before the engine block goes to the machine shop so we know what size the bore needs to be. We do this because depending on the end purpose of the engine, the clearances need to be adjusted. Say a nitrous shot of 300 needs more piston to wall clearance than an n/a engine does. All this is discussed with the customer before the first part is ordered, what the end use is going to be.
After all the pistons and bores are measured, each piston is given a letter, and each bore already has a number. Then each piston is taken and matched with the bores down to .0001" so that they average out to the target clearance. After that is finished, then we begin with the rod bearings by inserting them all into the rods after cleaning and then torque them to spec in a rod vise. Then the crank is cleaned, oil holes cleaned out, etc, and it is mic'd and all the diameters are written down, once again checked at 90 degree angles to confirm it is round. Then we set the dial bore gauge up to the diameter of the smallest journal, but usually we are only talking a few tenths of a thousandth, .0001.
Then the dial bore gauge is run into the rod bearing and the measurement it shows is your oil clearance. If the clearance is in spec, then that is written down and move on to the next, each rod has a letter as well, then once all clearances are written down, each rod is matched to a journal to give the best clearance in the target range. For instance, one rod is a bit on the high end of the clearance range, say .002 to .0025, so it's .0025, and we have a larger diameter rod journal, say 2.1235, we can put that rod on that journal, and it will net .002 clearance. follow me?
After that, all the main bearings are put in after the inside of the engine has been cleaned, and painted. Then the main caps are torqued onto the block. Next we set the dial bore gauge up with the appropriate crank main journal diameter and check each bearing for oil clearance. Main bearings can be moved around to net different clearances, but that usually doesn't work, but worth a try. The variance comes in the small differences in journal diameters in the block where the bearing sits. So what you have to do is get .001 under and .001 over, then mix and match until you get the clearances in spec. This also works for the rods too. I have to do this for just about every stroker engine I build because the cranks are on the top end of the range(bigger diamter) and will have no clearance when assembled.
So now you have all your rod journals done, main journals are done, and you can begin hand filing your rings. I use a manual grinder that holds the ring steady while it is ground and clearanced. go slow and steady, it's easy to make it too big. Set your ring gap spec from the sheet that comes from the manufacturer, what I set my gaps to for different applications is part of my business and I don't give them out. But you can use their recommendations and get it very close.
After that, then you put each piston measurement with each bore it best fits in and change the letter on it to the number of the cylinder, then you put the rod from that cylinder onto the piston for that cylinder, and so on. Then take the rings from each cylinder and put them on the piston for that cylinder as well. Then install crank, rod and piston assemblies and you have a blueprinted engine with all the spec's on it.
