What is the Fire order for 390 ford big block?

There's no single "Fire Order" for all 390 Ford big blocks. The firing order depends on the year of manufacture and whether it's a 2-barrel or 4-barrel carburetor setup. The most common firing orders are:

* 1-5-4-2-6-3-7-8: This is the most common firing order for many 390s.

* 1-3-7-2-6-5-4-8: Less common, but possible.

To be absolutely certain of the correct firing order for *your* specific 390 Ford big block engine, you should:

* Check the engine block: Sometimes the firing order is cast into the block itself.

* Consult a Ford parts manual: A parts manual specific to the year and model of your vehicle will have the correct firing order.

* Look at the distributor: While not always reliable, the distributor cap may have the firing order marked on it. However, this can be incorrect if someone has changed the distributor.

Without knowing the exact year and model of your vehicle, it's impossible to give you the definitive firing order. Using an incorrect firing order can lead to engine damage. It's crucial to verify this information before attempting any engine work.