School me on 340 exhaust manifolds

mrtires24 said

. If my car is a 1970 duster and the fender tag build date is oct 10...wouldn't that mean it was built in oct 10 1970...as in the owner ordered it earlier?

I understand that if this car was pre made for 1970 it would have been built in late 1969...how can I tell the year my car was built?

I have all documentation for the car ( build sheet, fender tag, numbers matching)

Click to expand...

No, the model year starts in June of the year before. They started 1970 model year production in June/July of 69. It ended in May/June of 70.

If you have a 70 Duster that was built in October, you should look for manifolds from sep 69 and earlier.

Parts can sit in the factory for a while, especially back then. I just saw a guy offering a 71 340 block that was cast in Jan of 71, but had a VIN code for a 72 model year car. Component parts can sit in the factory for months, sometimes years. If they are still at the proper change level for the next year, they are used. Or they use them up at the end of the year production or run them out at the beginning of the next year's production to save the cost of scrapping them...

Your car could theoretically have a 68 casting date exhaust manifold that sat on an engine that had to be torn down and recycled, then parts reused. As long as the casting date is not AFTER the build date of the car...

But then again, what if it was replaced under warranty??? 5 years/50,000 miles....