Page 185 - Diamond Pistons
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Automath Formulas
Automath 101 - Displacement (inches) Cubic inches = Bore2 x Stroke x .7854
(Multiply x 8 for a V-8 engine)
To  gure compression ratio, you will need to convert to cubic centimeters:
cc’s3 = (Bore x 2.54)2 x (Stroke x 2.54) x .7854
Automath 102 - Piston-to-Deck Volume Piston-to-Deck Volume = (Bore x 2.54)2 x
(Deck Clearance x 2.54) x .7854
If your piston is about the deck @ TDC, use a negative (-) number for your deck clearance.
Automath 103 - Compressed Gasket Volume Compressed Gasket volume: (Gasket Bore x 2.54)2 x (Compressed Gasket Thickness x 2.54)
x .7854
This assumes a “round” gasket bore.
Automath 104 - Top Ring Volume
Top Ring Volume = The di erence between the bore size and the top of the piston above the ring.
(Bore x 2.54)2 x (Top Ring Down x 2.54) x .7854 - {(Bore - .060”) x 2.54}2 x (Top Ring Down x 2.54) x .7854 Subtracting .060” from your bore size gives you a “normal” value for your tip land diameter.
Automath 105 - Engine Compression Ratio Compression Ratio = (Total swept volume + compressed volume) ÷ (compressed volume)
Total Swept Volume =
Cylinder Volume + Head Gasket Volume + Deck Volume + Top Ring Volume. Then: - Piston Dome Volume or + Piston Dish Volume
Compressed Volume =
Chamber Volume + Head Gasket Volume + Deck Volume + Top Ring Volume,
Then: Subtract ( - ) Piston Dome Volume or
Add ( + ) Piston Dish Volume
How to Select a Set of Diamond Pistons for Your Engine.
1. Locate the piston selection that matches your engine
3. Locate the compression dimension (C.D.) to fit your connecting rods, crankshaft, and engine block
Before selecting a piston, the desired compression dimension must be known - the compression dimension is the distance between the centerline of the pin bore and the top of the piston. To determine the compres- sion dimension for any engine combination,  rst calculate the block height, connecting rod length, and crankshaft stroke length.
2. Select the type type of piston that fits your application (Flat top, Dome, Dish, etc.)
5. After choosing your piston set, use the formulas above to confirm your compression ratio
4. Select the cylinder bore diameter
6. Choose the Diamond Part#, Ring Set, and Piston Pins to place your order–use the pin dimensions to locate the part number in the back of this catalog
7. For custom pistons refer to the last page of this catalog or call one of the experts at Diamond
DiamondRacing.net Tech support 586.792.6620
183
Big Block Chevy 20° COMPETITION SERIES
Bore Stroke Rod
C.D. Weight
Pin
COMPRESSION RATIO CC's 95cc
Ring Set
Part #
4.600 4.375 6.385 4.605 4.375 6.385 4.610 4.375 6.385 4.625 4.375 6.385 4.600 4.375 6.535 4.605 4.375 6.535 4.610 4.375 6.535 4.625 4.375 6.535 4.600 4.500 6.385 4.605 4.500 6.385 4.610 4.500 6.385 4.625 4.500 6.385 4.600 4.750 6.700 4.605 4.750 6.700 4.610 4.750 6.700 4.625 4.750 6.700 4.600 4.250 6.385 4.605 4.250 6.385 4.610 4.250 6.385 4.625 4.250 6.385
1.215 655 1.215 657 1.215 658 1.215 663 1.065 618 1.065 620 1.065 622 1.065 629 1.155 643 1.155 644 1.155 647 1.155 652 1.120 625 1.120 636 1.120 639 1.120 643 1.270 662 1.270 669 1.270 670 1.270 676
.990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750 .990 x 2.750
27.94cc 15.3 27.94cc 15.3 27.94cc 15.3 27.94cc 15.4 27.94cc 15.3 27.94cc 15.3 27.94cc 15.3 27.94cc 15.4 27.94cc 15.8 27.94cc 15.9 27.94cc 15.9 27.94cc 16.0 27.94cc 16.9 27.94cc 17.0 27.94cc 17.0 27.94cc 17.1 27.94cc 14.6 27.94cc 14.6 27.94cc 14.7 27.94cc 14.7
09224600 09224600 09224610 09224625 09224600 09224600 09224610 09224625 09224600 09224600 09224610 09224625 09224600 09224600 09224610 09224625 09224600 09224600 09224610 09224625
21000 21001 21002 21003 21004 21005 21006 21007 21008 21009 21010 21011 21012 21013 21014 21015 21016 21017 21018 21019
• • • • • • • • • • •
Designed for use with Brodix SR20 and Dart 20° cylinder heads Vertical gas ports for maximum ring seal
Inboard forging design for maximum strength
Suitable for small to medium nitrous applications
Moly skirt coating for friction loss and skirt wear protection Premium .043mm x .043mm x 3.0mm ring package
H-13 tool steel .185W wrist pins included
Top ring down dimension: .295” - .280” on 1.065cd
Will work with up to a intake valve size of 2.400” and exhaust valve size of 1.800” Valve pocket depth: 0.345” intake and -.030” exhaust
Made from 2618 alloy
ist pins available as a upgrade to any piston part number -
COMPETITION SERIES


































































































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