Over it's lifetime, the SBC used 2 different Oil Pan Gaskets. The difference between them is the thickness of the gasket in the area that meets the timing cover:
- A "thin seal" is about 1/4 in. thick.
- A "thick seal" is about 3/8 in. thick.
Which pans use which gaskets?
- The OEM oil pans made between 1955 and 1974 used the "thin seal."
- The OEM oil pans made in 1975 and later used the "thick seal."
- Most aftermarket oil pans use the "thick seal."
Even though there is a clean break in the year ranges, it's best to double check by measuring. Measure the height and width of the area of the oil pan shown below.
| Height | Width | Gasket Type Required |
| 2 1/4 in. | 5 1/2 in. | Thin Seal |
| 2 3/8 in. | 5 3/4 in. | Thick Seal |
Why does it matter?
Either way, if you use the wrong type of gasket, it will cause an oil leak.
- If you use a thin seal when a thick seal is required, it will leave a gap around the timing cover.
- If you use a thick seal when a thin seal is required, it will pull up on the corners of the front of the oil pan.