Editing Basics of parts stack SBC

STACK: The addition of 3 values to arrive at the STACK dimension of parts that you will fit into the cylinder block. PISTON COMPRESSION HEIGHT, rod center to center length and crankshaft RADIUS are added together to arrive at a STACK height. Generally speaking, a builder would want the total STACK dimension to be just short of the BLOCK DECK HEIGHT or exactly the same measurement as the BLOCK DECK HEIGHT, called "zero deck". Some builders have fitted a taller STACK into a block to allow the piston to come up out of the block slightly with the piston at top dead center. This might be done to adjust the squish when using a thicker head gasket, like maybe a 0.050" (fifty thousandths of an inch) thick or 0.060" (sixty thousandths of an inch) thick copper gasket with o-rings for a blower motor. If using domed, or pop-up pistons, the STACK is measured to the piston crown, NOT including the dome. Some pistons are manufactured with a COMPRESSION HEIGHT taller than a standard piston. This additional measurement needs to be taken into consideration when totalling the height of your STACK of parts. http://www.rosspistons.com /images/co...ion-height.jpg BLOCK DECK HEIGHT: Measurement from the centerline of the main bearing bore of the block to the flat part of the block deck where the heads bolt on. Blueprint dimension of a Gen I small block Chevy is 9.025". Not to be confused with PISTON DECK HEIGHT, which is the measurement from the piston crown to the block deck with the piston at top dead center. BLOCK DECK HEIGHT is shown here, but is mis-labeled as simply "deck height". It should have been labeled "BLOCK DECK HEIGHT".... https://www.lunatipower.com /Images/T...DeckHeight.gif PISTON: Pistons come in 3 flavors, cast aluminum, cast hypereutectic aluminum and forged aluminum. Hypereutectic means that there is a very large amount of silicon in the mix when the manufacturer casts the piston, which gives the piston a different set of operating characteristics over a conventional mix with a standard amount of silicon added to make a conventional cast piston. In addition to the obvious diameter measurement, there is a measurement of the centerline of the wrist pin to the crown of the piston. This measurement is called COMPRESSION HEIGHT.... OR CH for short. This diagram shows CH..... http://i263.photobucket.com /albums/i...istons-1-1.jpg That measurement is one of 3 measurements an engine builder must know to add up the STACK of parts to be used in the cylinder block. Pistons come in many different COMPRESSION HEIGHTS to allow their use in different combinations of stacks. CONNECTING ROD: Rods come in 3 flavors, cast steel, forged steel and in the case of aluminum racing rods, extruded. 99% of the rods used by us hot rodders will be forged from one steel mix or another, with the formula varying according to how the manufacturer wants the rod to perform in its lifetime. Rods come in many different center-to-center lengths so that we can custom tailor the measurement of the stack of parts we will use in our motor. You can see the center to center length of a connecting rod shown here as dimension A...... http://www.lunatipower.com /Images/Te...Tolerances.gif CRANKSHAFT: Cranks come in 3 different flavors, cast steel, forged steel and billet steel. The vast majority of cranks used in the hot rod hobby will be cast steel. Half the stroke of the crank, or the RADIUS of the crank, will be used to determine your STACK. If a crank stroke is 3.48", then the radius of that crank will be 1.74". In the left part of this diagram, the arrow points to the centerline of the crankshaft main bearing journal. Another arrow points to the crankpin where the big end of the rod bolts on. http://www.mathpages.com /home/kmath1...s/image001.gif The measurement between these two points is the RADIUS of the crankshaft. As stated above, the radius of a 350 crank would be 1.74", or half the 3.48" stroke. A 383 crank, with its 3.75" stroke, would have a RADIUS of 1.875". A 283 crank, with a 3.00" stroke, would have a RADIUS of 1.50". Radius is shown in this example as "crank throw"..... http://www.fordmuscle.com /archives/2...es/figure1.gif PISTON DECK HEIGHT: Not to be confused with block deck height, piston deck height is the measurement from the crown of the piston to the block deck where the heads bolt on, with the piston at top dead center. PLEASE PAY ATTENTION. THERE ARE 2 DIFFERENT DECK HEIGHTS. BLOCK DECK HEIGHT AND PISTON DECK HEIGHT. PLEASE BE SPECIFIC WHEN DISCUSSING "DECK HEIGHT". Piston deck height is labeled incorrectly here as simply "deck height". It should be labeled "Piston Deck Height", not to be confused with block deck height. http://i109.photobucket.com /albums/n...isc/Piston.jpg SQUISH: The distance from the piston crown to the underside of the cylinder head with the piston at top dead center and with the head gasket in place and its thickness included in the measurement. If the piston crown were down in the bore by 0.010" (ten thousandths of an inch) with the piston at top dead center and you used a 0.028" (twenty eight thousandths of an inch) gasket thickness, adding the two together would yield a 0.038" squish measurement (thirty eight thousandths of an inch). The closer the piston comes to the underside of the head (without crashing into the head), the better the motor will perform. The action is that the piston comes up very close to the underside of the head and squishes out the mixture in that area, jetting it across the chamber toward the spark plug and creating turbulence to help eliminate rich and lean pockets of mixture in the chamber so that the whole mess burns evenly and offers less chance for the mixture to detonate or pre-ignite. QUENCH: The terms quench and squish are often used interchangeably, but they actually have different technical meanings. Quench refers to the passing of heat from the combustion chamber into the surrounding metal, some of which finds its way into the cooling system. The more quench that is in effect, the more heat passes into the cooling system and vise versa. On one hand, having a quench-type combustion chamber and piston shape and tight quench distance may be looked at as a detriment to power production (heat IS energy, after all). But in the case of the IC engines we are working with, the loss of heat energy is more than offset by the decrease in the tendency to encounter detonation- which will kill power at a much greater rate and amount than the loss of some combustion chamber heat to the quench effect. OK, with that under our belts, we can see that when you build a motor, you choose a STACK of parts that will fit into your block and bring the piston crown up close to the top of the cylinder bore. The stack will normally be a little shorter than the BLOCK DECK HEIGHT, with the overage being the PISTON DECK HEIGHT. In other words, if the BLOCK DECK HEIGHT is 9.025" (the blueprint dimension from the factory) and your STACK of parts measures 9.000", then there will be a distance of 0.025" (twenty five thousandths of an inch) between the top of the piston (the crown of the piston) and the top of the block deck where the heads bolt on. If you had a PISTON DECK HEIGHT of 0.025" and added a 0.020" (twenty thousandths of an inch) thickness head gasket, then you would add the two measurements together to find a SQUISH dimension of 0.045" (forty five thousandths of an inch). This would play into the generally-accepted practice of using a SQUISH dimension between 0.035" and 0.045" (thirty five thousandths of and inch to forty five thousandths of an inch). Tighter than this can cause piston to head interference. Looser than this loses any advantage that may have been afforded the motor by a tighter squish. This is where most fellows go wrong with their build. If they have a 0.025" PISTON DECK HEIGHT and use a 0.040" (forty thousandths of an inch) thickness head gasket, the two added together yields a squish dimension of 0.065" (sixty five thousandths of an inch), a figure that does little to actually "squish" the mixture across the chamber. If you find the need to use a thicker composition gasket, such a 0.039", 0.040" or 0.041", then you would want to cut the BLOCK DECK HEIGHT to "zero" PISTON DECK HEIGHT. This would put the piston crown even with the top of the cylinder bore with the piston at top dead center and the SQUISH dimension would be made with the gasket thickness only. So, let's say that you began by verifying the roundness and parallelism of the main bearing bore at the bottom of the block and correcting as necessary, then cut the BLOCK DECK HEIGHT to 9.000" as part of your engine build. Now, you want to use a 9.000" STACK of parts to fill the block to arrive at "zero deck", using the head gasket thickness to establish your SQUISH dimension. One of the main reasons to zero deck the block to the stack of parts is that all aluminum head manufacturers recommend a 0.039", 0.040" or 0.041" head gasket thickness and you must zero deck the block to arrive at the proper SQUISH. If you get the motor together with a stock PISTON DECK HEIGHT of, for instance, 0.025" (twenty five thousandths of an inch) and used iron heads with a thin head gasket, then you would have a very wide SQUISH dimension when you used the thick head gasket called for by the aluminum head manufacturer. Now, back to the STACK. You could use a 1.74" radius 350 crank, 5.7" rod and a piston with a 1.560" COMPRESSION HEIGHT to arrive at a 9.000" STACK. Maybe you want to build a long rod 350, so you might use a 1.74" radius 350 crank, 6.0" rod and 1.260" piston COMPRESSION HEIGHT to arrive at a 9.000" STACK. Or you could use a 1.875" radius 383 crank, 5.7" rod and a piston with a 1.425" COMPRESSION HEIGHT to arrive at a 9.000" STACK. Or you could use a 1.875" radius 383 crank, 6.00" rod and 1.125" COMPRESSION HEIGHT piston to make your 9.000" STACK. Hopefully by now, you can see how the whole mess comes together. IT IS INCUMBENT UPON THE BUILDER TO FIGURE ALL THIS OUT BEFORE ANY PARTS ARE BOUGHT. Last

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