Sbc oil pan question

Small block chevys used two oil pans, one with a thick(3/8in) front pan seal and one with a thin(1/4in) front pan seal. Question is-which one was used first and what year did it change?

 

Thin seal was first. The change was around 1974. It is only the pan that changed, so if you are putting a late pan on an early engine (for example) you would use the thick seal.

 

FYI, the new FelPro one piece replacement gaskets are awesome and worth the extra money.

 

Thanks for the info, I'm trying to answer the question for a guy at work. I loaned somebody my "How to Build a Smallblock " book and it never came home>

 

The gasket makers say thick front seal is '75 - '79 LH dipstick and '80 - '85 RH dipstick. The '86 - '97 also have "thick" front seal area but most use a 1 pc gasket. "Most" of the aftermarket chrome pans use the thick seal.