* Specific Big Block Engine: Chevrolet, Ford, Chrysler big blocks all have different bellhousing bolt patterns. Even within a manufacturer (e.g., Chevrolet), different years and models might have slight variations.
* Transmission Adaptor Plate (if used): Many combinations require an adaptor plate to mate the transmission to the engine. The adaptor plate dictates the bolt size needed.
* Specific Transmission: While you specified a Turbo 400, variations exist even within this transmission model across different years.
To find the correct bolt size, you MUST:
1. Identify your specific big block engine (make, model, year).
2. Identify the year of your Turbo 400 transmission.
3. Check your existing bellhousing (if it's a direct bolt-on). The bolts already in it are your answer.
4. Consult a parts catalog or a transmission specialist. Provide the engine and transmission details to get the correct information. A parts catalog specific to your vehicle year and engine is the best resource.
Attempting to guess the bolt size could lead to significant engine and transmission damage. Incorrect bolts could cause the transmission to come loose, potentially resulting in a very dangerous accident. Always verify with the correct resources.
