Small Block Chevy Crankshaft Flange Identification: Complete Guide
Depending on the year and engine size of your small block Chevy truck, it may have a different crankshaft flange. The flange may vary in terms of shape, size, and design. So then, how do you make small block chevy crankshaft flange identification?
Checking the casting number is one of the best ways to identify the crankshaft flange of your small block Chevy. The ID numbers vary from one Chevy truck to another. You can also recognize the flange by inspecting its journal diameter and the type of material it is made of.
But wait, there is more! So, stay here to learn more about a crankshaft flange, how to identify it, and why identification is necessary.
Table for Crankshaft Flange Identification In Small Block Chevy
Below is a table to help you quickly identify the crankshaft flange of different small-block Chevy models.
Small Block Chevy Year Model | Engine Size | Casting Number | Main/Rod Journal Size (Inches) | Type of Material |
1957-1967 | 283 | 3727449 | 2.30/2.00 | Forged steel |
1967-1969 | 302 | 3815822 | 2.30/2.00 | Forged steel |
1968-1969 | 302 | 3941178 | 2.45/2.10 | Forged steel |
1962-1967 | 327 | 3782680 | 2.30/2.00 | Forged steel |
1968-1976 | 350 | 3941182 | 2.45/2.10 | Forged |
1976 -1985 | 305 | 3932442 | 2.45/2.10 | Cast iron |
1986-1989 | 350 | 14088526 | 2.45/2.10 | Cast iron |
1955 -1957 | 265/283 | 3735236 | 2.3/2.0 | Forged |
1968-1973 | 307/327 | 1130 | 2.45/2.10 | Nodular iron |
1968-1976 | 305/350 | 1181 | 2.45/2.10 | Nodular iron |
1986 & up | 305/350 | 14088535 | 2.45/2.10 | Nodular iron |
1990 – 1995 | 350 | 10106122 | 2.76/2.10 | Forged |
1969 -1985 | 305/350 | 3932442 | 2.45/2.10 | Nodular iron |
1964 -1967 | 283 | 3876768 | 2.3/2.0 | Nodular iron |
1956 – 1963 | 265/283 | 3836266 | 2.3/2.0 | Forged |
1990-1995 | 346 | 12552216 | 2.56/2.10 | Cast iron |
1970 – 1980 | 400 | 3951529 | 2.65/2.10 | Nodular iron |
What Is A Crankshaft Flange In A Small Block Chevy?
According to Science Direct, a crankshaft is a mechanical component located near the bottom end of your small block Chevy. The primary purpose of the crankshaft is to convert the energy produced by the combustion engine into rotary motion. Consequently, this helps drive your Chevy’s wheels via the gearbox.
Typically, the crankshaft attaches to the engine via large bearings. It also connects to the flywheel via precision-machined flanges, hence the crankshaft flange. The flange helps smoothen power delivery while also reducing vibration.
Small Block Chevy Crankshaft Flange Identification Methods
Now that you know what a crankshaft flange is in small block Chevy, how do you recognize it? Here are simple methods you could use.
Check casting number
All small block Chevy crankshafts feature a casting or ID number. You can find this number on the rough surface between the bearings or one of the counterweights around the flange area.
The casting number differs based on the engine size of your small block Chevy and the year of manufacture. For instance, the casting number of a 1968-1969 Chevy with a 302 small block engine is 3941178. Meanwhile, an 1986-1989 350 small block Chevy has a casting number of 14088526.
Journal size
A journal is a piece of the crankshaft that rotates inside the bearing. The journal comes in two types, including main and rod. Overall, the primary journal has a larger diameter than its rod counterpart.
Like with casting numbers, the size of the principal and rod journals differs based on the engine size of your small block Chevy. However, most Chevy models’ main journals range between 2.30 to 2.45 inches in diameter. For the rod journals, the size ranges from 2.00 to 2.10 inches.
Parting lines
If your small block Chevy does not have a casting number cast or stamped into it, you can use the parting line strategy. For instance, you can tell if the crankshaft flange is forged if it has a broader parting line of about 1/2-inch or more. The line should also have an uneven shape.
On the other hand, if the crankshaft flange is cast, the parting line should be narrower, thin, or sharp. In both cases, the parting line will go down the length of your Chevy crank.
Seal Design
The production of the first generation of small-block Chevy began in 1955. All models in this generation featured a two-piece rearmost neoprene seal on the rear flange area. However, all small block Chevy vehicles produced from 1986 have a one-piece back end main seal on the rear flange.
Now, while you can use a two-piece main seal in a one-piece rear seal block, the vice versa is not possible. You only need an adapter.
Type of material
The crankshaft of a small block Chevy should either be made of cast iron, nodular cast iron, or forged steel. You can tell if a crankshaft flange is forged by tapping the non-machined part with a small hammer. The crank will produce a high-pitched ring sound.
But if the crankshaft is nodular or cast iron, you should get a dull thump sound. However, unlike cast iron, nodular iron material has higher strength and toughness comparable to forged steel.
Why Is Small Block Chevy Crankshaft Identification Important?
The primary reason you must determine what type of crankshaft flange your small block Chevy has is due to compatibility. This is because, at some point, you may need to replace the crankshaft when it gets worn out. However, you cannot just get the first unit you come across.
Do you know why? Because some small block Chevy trucks have a crankshaft with a one-piece main seal and others two-piece. And as it turns out, a one-piece rear seal on the flange is incompatible with vehicles featuring two-piece seals.
Which Is Better Between Cast And Forged Crankshaft Flange?
Overall, a forged crankshaft flange is better than cast iron for many reasons. This is despite being relatively more expensive than their cast iron counterparts.
First of all, cast flanges undergo a one-time shaping process, while their forged counterparts must be generated several times. For this reason, cranks made of forged steel have 52% higher yield strength than cast iron pieces.
Additionally, forged units boast higher ductility. Their elongation rating before failure ranges between 20 to 22%. Cast crankshaft flanges have an elongation of 5 to 6%.
Elongation rating is simply a measure of how brittle the cranks are.
Other things that make forged crank flange the best choice include the following:
- Heavier than cast units
- Can handle more loads
- Highly resistant to fatigue
- Excellent impact resistance
Frequently Asked Questions (FAQs)
Below, you can find answers to some frequently asked questions about crankshaft flange identification in small block Chevy.
It should have a casting number of 3911001 and be made of cast iron instead of forged steel. The flange should also have a 2.45-inch main journal and a 2.10-inches rod journal.
There are two types: the forged, which are more robust, and the cast crankshafts. Cast units have been there long since they are cheaper and easier to produce.
You check for the ID or casting number. But if the number is not there, you could check the journal size, seal design, or parting lines on the crank.
Conclusion
A crankshaft flange is vital in your small block Chevy internal combustion engine. Therefore, learning about small block Chevy crankshaft flange identification is critical, especially when replacing it with an aftermarket unit. Besides construction, you can identify the flange by looking out for the casting number and size of the journal.
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