Basic engine nomenclature
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[[Category:Undeveloped General hotrodding articles]] | [[Category:Undeveloped General hotrodding articles]] | ||
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| + | 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 | ||
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| + | 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 | ||
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| + | 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. | ||
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| + | 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 | ||
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| + | 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 | ||
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| + | 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 | ||
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| + | 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. | ||
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| + | 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. | ||
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