What is the diameter of the main journal on a SBC 400 crankshaft?
The main journal on a Small Block Chevy (SBC) 400 crankshaft has a diameter of 2.4375 inches (62 mm). This is a critical specification for the proper functioning and longevity of the engine's rotating assembly.
Understanding the SBC 400 Crankshaft
The SBC 400 is a popular engine block used in various Chevrolet vehicles, including the Chevelle, Camaro, and Corvette, from the late 1960s to the mid-1980s. The crankshaft is a crucial component that converts the reciprocating motion of the pistons into rotational motion, which is then transmitted to the drivetrain.
The main journals on the crankshaft are the bearing surfaces that support the weight of the rotating assembly and allow it to spin smoothly. The diameter of these journals is a critical specification that must be maintained within tight tolerances to ensure proper oil flow, bearing clearance, and overall engine performance and reliability.
Importance of the Main Journal Diameter
The main journal diameter on the SBC 400 crankshaft is 2.4375 inches (62 mm). This dimension is essential for several reasons:
- Bearing Clearance: The main bearings that support the crankshaft must have the correct clearance to allow for proper oil flow and lubrication. The main journal diameter, along with the bearing bore diameter, determines the bearing clearance.
- Oil Flow: The main journal diameter affects the oil flow to the crankshaft bearings, which is crucial for reducing friction and wear.
- Strength and Durability: The main journal diameter is directly related to the crankshaft's strength and ability to withstand the high stresses and loads generated during engine operation.
Maintaining the correct main journal diameter is essential for ensuring the proper functioning and longevity of the SBC 400 engine.
Crankshaft Rebuilding and Regrinding
Over time, the main journals on a crankshaft can become worn or damaged, necessitating a rebuild or regrinding process. During this process, the main journal diameters may need to be reduced to remove any damage or wear, while still maintaining the critical 2.4375-inch (62 mm) specification.
Proper crankshaft rebuilding and regrinding techniques are essential to ensure the engine's continued reliable performance and longevity.
What size are the SBC 400 mains?
I've noticed that you can buy a SBC block say a 400 block but with the smaller 2.450" (350) mains instead of the regular 2.650" mains that are standard on the SBC 400. You can even buy a 4.000" stroke crank with the smaller 2.450" mains.
What's the difference between a 400 small block and a 400 big-block?
So this is a 496. And this is a 350 making this a small block. And this a big block. Now there is one exception to the big block that's under 400 cubic inch and that's the 396.
What is the diameter of the journal on a SBC crank?
On sbc 350 std crank journal size for 1-4 is 2.4484" - 2.4493" and #5 ( oil pump location ) is 2.4479" - 2.4488".
What size is the main journal on a 409?
2.5-inch
The 348/409s have the same bore-spacing, 2.20-inch rod journals, and rear main seal as the later Mark IV big-block. The front snout and seal is the same as a small-block. Only the 2.5-inch main-bearing journal diameter is unique.
How do you measure the main journal diameter?
The diameter of the main crankshaft journals should be calibrated by measuring with a micrometer taking two readings at right angles to each other and, again, the measurements recorded and looking for any ovality of the journal and also the crank pin.
What should be the size of a journal?
Medium is the most popular and probably the most widely useful size, measuring about 6x9 inches (A5 paper, 5.8 x 8.3 inches). This size is small enough to be portable but still offers enough writing space to jot down ideas, make notes, or write short pieces.
What is the bore of the 400 SBC cylinder?
4.125" bore, 3.75" stroke.
What is the bore diameter of a 400 small-block?
The engine sports 400 cubic inches thanks to a combination of a 4.125-inch bore and 3.750-inch stroke.
What is the diameter of the crankshaft main-bearing journal?
Stock journal diameters are: 1.8758/1.8764" and 2.1265/2.1270" respectively. There are no bearing ID specs available, as they are designed to crush slightly when the caps are torqued down. That's why the only way to determine actual bearing clearance is with Plastigauge or an equivalent product.
What is a 350 bored 60 over with a 400 crank?
With a 400 crank in a . 060 over 350 it would be a 388.
