What compression piston do I need?
The below topics will help you answer the question above:
- Calculate Block Height
- Calculate Connecting Rod Length
- Calculate Stroke Length
Before selecting a piston, the desired compression height must be known. As shown, compression height is the distance between the centerline of the pin bore and the top of the piston. To determine the compression, three things about the engine must first be known: block height, connecting rod length and crankshaft stroke length.
1. Calculate Block Height Top↑
Deck height is measured from the crankshaft centerline to the deck (cylinder head mounting surface) of the block.
Stock Chevrolet V-8 Block Heights
| Displacement Cubic Inches | Liters | Deck Height (inches) |
|---|
| 302 | 4.9 | 9.025 |
| 305 | 5.0 | 9.025 |
| 327 | 5.4 | 9.025 |
| 350 | 5.7 | 9.025 |
| 350(LT5) | 5.7 | 9.025 |
| 350(LS1) | 5.7 | 9.240 |
| 364(LQ4) | 6.0 | 9.240 |
| 383 | 6.3 | 9.025 |
| 400 | 6.6 | 9.025 |
| 396 | 6.5 | 9.800 |
| 402 | 6.6 | 9.800 |
| 427 | 7.0 | 9.800 |
| 454 | 7.4 | 9.800 |
| 502 | 8.2 | 9.800 |
Stock Ford V-8 Block Heights
| Displacement Cubic Inches | Liters | Deck Height (inches) |
|---|
| 289 | 4.7 | 8.206 |
| 302 | 5.0 | 8.206 |
| 302(Boss) | 5.0 | 8.201-8.210 |
| 302(SVO) | 5.0 | 8.201-8.210 |
| 351 W ('69-'70) | 5.8 | 9.480 |
| 351 W ('71-'96 | 5.8 | 9.503 |
| 351 (SVO 9.2) | 5.8 | 9.206 |
| 351C (Boss) | 5.8 | 9.206 |
| 351M | 5.8 | 10.297 |
| 429 STD ('68-'70) | 7.0 | 10.300 |
| 429 STD ('70 1/2-'71) | 7.0 | 10.310 |
| 429 CJ/SCJ ('72-'73) | 7.0 | 10.322 |
| 429 Boss (S) | 7.0 | 10.300 |
| 429 Boss (T) | 7.0 | 10.300 |
| 460 | 7.5 | 10.322 |
| 281 (modular) | 4.6 | 8.937 |
| 331 (modular) | 5.4 | 10.079 |
2. Calculating Connecting Rod Length Top↑
Connecting rod length is measured between the centers of the "big end" (journal end - rotating) and the "little end" (piston pin end - reciprocating).
Stock Chevrolet V-8 Connecting Rod Lengths
| Displacement Cubic Inches | Liters | Big End Dia. (inches) | Rod Length (inches) |
|---|
| 302 | 4.9 | 2.1000 | 5.7000 |
| 305 | 5.0 | 2.1000 | 5.7000 |
| 327 | 5.4 | 2.1000 | 5.7000 |
| 350 | 5.7 | 2.1000 | 5.7000 |
| 350(LT5) | 5.7 | 2.1000 | 5.7400 |
| 350(LS1) | 5.7 | 2.2500 | 6.0980 |
| 383 | 6.3 | 2.1000 | 6.0000 |
| 400 | 6.6 | 2.1000 | 5.5650 |
| 396 | 6.5 | 2.2000 | 6.1350 |
| 402 | 6.6 | 2.2000 | 6.1350 |
| 427 | 7.0 | 2.2000 | 6.1350 |
| 454 | 7.4 | 2.2000 | 6.1350 |
| 502 | 8.2 | 2.2000 | 6.1350 |
Stock Ford V-8 Connecting Rod Lengths
| Displacement Cubic Inches | Liters | Big End Dia. (inches) | Rod Length (inches) |
|---|
| 289 | 4.7 | 2.1232 | 5.1550 |
| 302 | 5.0 | 2.1232 | 5.0900 |
| 302(Boss) | 5.0 | 2.1226 | 5.1500 |
| 302(SVO) | 5.0 | 2.1226 | 5.1500 |
| 351 W ('69-'70) | 5.8 | 2.3110 | 5.9560 |
| 351 W ('71-'96 | 5.8 | 2.3110 | 5.9560 |
| 351 (SVO 9.2) | 5.8 | 2.3110 | 5.7800 |
| 351C (Boss) | 5.8 | 2.3110 | 5.7800 |
| 351M | 5.8 | 2.3107 | 6.5800 |
| 429 STD ('68-'70) | 7.0 | 2.500 | 6.6050 |
| 429 STD ('70 1/2-'71) | 7.0 | 2.500 | 6.6050 |
| 429 CJ/SCJ ('72-'73) | 7.0 | 2.500 | 6.6050 |
| 429 Boss (S) | 7.0 | 2.500 | 6.5490 |
| 429 Boss (T) | 7.0 | 2.500 | 6.6050 |
| 460 | 7.5 | 2.500 | 6.6050 |
| 281 (modular) | 4.6 | 2.0863 | 5.9331 |
| 331 (modular) | 5.4 | 2.0863 | 6.6575 |
3. Calculate Stroke Length Top↑
Stroke length is twice the distance from the centerline of the crankshaft main bearing journals to the centerline of the connecting rod journals. It is also the distance the piston moves up and down in the cylinder.
Stock Chevrolet V-8 Bore & Stroke
| Displacement Cubic Inches | Liters | Bore (inches) | Stroke (inches) |
|---|
| 302 | 4.9 | 4.000 | 3.000 |
| 305 | 5.0 | 3.740 | 3.480 |
| 327 | 5.4 | 4.000 | 3.250 |
| 350 | 5.7 | 4.000 | 3.480 |
| 350(LT5) | 5.7 | 3.898 | 3.661 |
| 350(LS1) | 5.7 | 3.898 | 3.622 |
| 364(LQ4) | 6.0 | 4.000 | 3.622 |
| 383 | 6.3 | 4.000 | 3.800 |
| 400 | 6.6 | 4.125 | 3.750 |
| 396 | 6.5 | 4.094 | 3.766 |
| 402 | 6.6 | 4.125 | 3.766 |
| 427 | 7.0 | 4.250 | 3.766 |
| 454 | 7.4 | 4.250 | 4.000 |
| 502 | 8.2 | 4.470 | 4.000 |
Stock Ford V-8 Bore & Stroke
| Displacement Cubic Inches | Liters | Bore (inches) | Stroke (inches) |
|---|
| 289 | 4.7 | 4.000 | 2.870 |
| 302 | 5.0 | 4.000 | 3.000 |
| 302(Boss) | 5.0 | 4.000 | 3.000 |
| 302(SVO) | 5.0 | 4.000 | 3.000 |
| 351 W ('69-'70) | 5.8 | 4.000 | 3.500 |
| 351 W ('71-'96 | 5.8 | 4.000 | 3.500 |
| 351 (SVO 9.2) | 5.8 | 4.000 | 3.500 |
| 351C (Boss) | 5.8 | 4.000 | 3.500 |
| 351M | 5.8 | 4.000 | 3.500 |
| 429 STD ('68-'70) | 7.0 | 4.360 | 3.590 |
| 429 STD ('70 1/2-'71) | 7.0 | 4.360 | 3.590 |
| 429 CJ/SCJ ('72-'73) | 7.0 | 4.360 | 3.590 |
| 429 Boss (S) | 7.0 | 4.360 | 3.590 |
| 429 Boss (T) | 7.0 | 4.360 | 3.590 |
| 460 | 7.5 | 4.360 | 3.850 |
| 281 (modular) | 4.6 | 3.552 | 3.543 |
| 331 (modular) | 5.4 | 3.552 | 4.165 |
How Compression Height Is Calculated:
| Compression height = block height - rod length - (0.5 X stroke) |
| |
| | Example: | block height = 11.685" |
| | | rod length = 7.500" |
| | | stroke = 5.500" |
| |
| Compression height = block height - rod length - (0.5 X stroke) |
| Compression height = 11.685 - 7.500 - (0.5 X 5.500) |
| Compression height = 1.435" |