383/388 Chevy stroker
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Another way to do this is to use a longer 6.00" rod combined with a piston having a 1.125" compression height. So, 1.875" + 6.000" + 1.125" = 9.000". The piston deck height is still 0.025" with this combination of parts. Using a 6" rod also has advantages if internally balancing is going to be done; there's more room for the crankshaft counterweights. Some builders prefer not to use a 6" rod, their thinking being the pin intruded into the oil ring groove, meaning pinned rings or support rails must be used to allow the oil control ring package to do its job, and the added complexity isn't worth the possible advantages from a higher rod/stroke ratio and/or lighter pistons, etc. However, Ross offers a 383 stroker piston with a 1.120" compression height that doesn't require rail supports. The least expensive way to build a 383 stroker is to use an externally-balanced 400 harmonic balancer and a 400 flexplate/flywheel. | Another way to do this is to use a longer 6.00" rod combined with a piston having a 1.125" compression height. So, 1.875" + 6.000" + 1.125" = 9.000". The piston deck height is still 0.025" with this combination of parts. Using a 6" rod also has advantages if internally balancing is going to be done; there's more room for the crankshaft counterweights. Some builders prefer not to use a 6" rod, their thinking being the pin intruded into the oil ring groove, meaning pinned rings or support rails must be used to allow the oil control ring package to do its job, and the added complexity isn't worth the possible advantages from a higher rod/stroke ratio and/or lighter pistons, etc. However, Ross offers a 383 stroker piston with a 1.120" compression height that doesn't require rail supports. The least expensive way to build a 383 stroker is to use an externally-balanced 400 harmonic balancer and a 400 flexplate/flywheel. | ||
| − | Yet another option, although one of the least popular, is to use the stock SBC 400 rod with a 350 SBC piston. The stack of parts looks like: 1.875" + 5.565" + 1.56 = 9.00". The main complaint about using this combo is the rod length. Most builders agree the 5.565" rod/3.75" stroke ratio is borderline unacceptable at 1.48:1, | + | Yet another option, although one of the least popular, is to use the stock SBC 400 rod with a 350 SBC piston. The stack of parts looks like: 1.875" + 5.565" + 1.56 = 9.00". The main complaint about using this combo is the rod length. |
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| + | ==A word on rod/stroke ratios== | ||
| + | Most SBC engine builders agree the 5.565" rod/3.75" stroke ratio is borderline unacceptable at 1.48:1. For comparisons sake, a stock SBC 350 has a ratio of 1.64:1, and the 6" rod 383 stroker is at 1.6:1. The SBC 302 rod/stroke ratio is 1.9:1. It is generally thought that a ratio of 1.5:1 to 1.55:1 is about as low of a rod/stroke ratio that should be used in a performance build that will redline at 5500 rpm or more. | ||
==Aftermarket parts combos== | ==Aftermarket parts combos== | ||
A popular parts combo for a 383/388 stroker is the Scat cast steel crankshaft and Scat I-beam forged Pro Stock rods. The Scat counterweights will clear the pistons using a 5.7" rod and the rods will clear the cam, so no grinding on the rods for cam clearance will be necessary. You may need to do a little grinding on the inside of the block at the pan rail to clear the big end of the rod, but it will be minimal. | A popular parts combo for a 383/388 stroker is the Scat cast steel crankshaft and Scat I-beam forged Pro Stock rods. The Scat counterweights will clear the pistons using a 5.7" rod and the rods will clear the cam, so no grinding on the rods for cam clearance will be necessary. You may need to do a little grinding on the inside of the block at the pan rail to clear the big end of the rod, but it will be minimal. | ||
| − | ==Zero decking the block== | + | ==Zero decking the block/"quench"== |
| − | It is common engine building practice to cut the block decks to zero piston deck height and to use a head gasket that compresses to around 0.040". This allows a quench or squish, or "squench" of 0.040". Squish is the high speed jetting of fuel air mixture from the dead zone opposite the combustion chamber. When the piston approaches top dead center, the clearance between the crown of the piston and the underside of the cylinder head diminishes to just short of a collision. This squeezes or "squishes" the mixture that is there, across the cylinder toward the spark plug. This high-speed jetting of the mixture not only eliminates any dead spots in the chamber, but also creates turbulence to achieve a more homogeneous mixing of the fuel/air mixture so that there are no lean or rich areas in the chamber. When using steel rods on a street/strip performance engine, having a tight squish of 0.035" minimum to 0.045"-0.050" will allow a high performance street/strip motor that will run on pump gas without detonation, providing that all the other important areas are also covered- like the static and dynamic compression ratios. | + | It is common engine building practice to cut the block decks to zero piston deck height and to use a head gasket that compresses to around 0.040". This allows a [[quench]] or squish, or "squench" measurement of 0.040". Squish is the high speed jetting of fuel air mixture from the dead zone opposite the combustion chamber. When the piston approaches top dead center, the clearance between the crown of the piston and the underside of the cylinder head diminishes to just short of a collision. This squeezes or "squishes" the mixture that is there, across the cylinder toward the spark plug. This high-speed jetting of the mixture not only eliminates any dead spots in the chamber, but also creates turbulence to achieve a more homogeneous mixing of the fuel/air mixture so that there are no lean or rich areas in the chamber. When using steel rods on a street/strip performance engine, having a tight squish of 0.035" minimum to 0.045"-0.050" will allow a high performance street/strip motor that will run on pump gas without detonation, providing that all the other important areas are also covered- like the static and dynamic compression ratios. |
[[Category:Engine]] | [[Category:Engine]] | ||
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