How related were the Seven, Big Seven and Eight Engines?

[Bill Sheehan]

I see, thanks for clarifying.

Section through the Austin Seven Engine (Three Bearing) page 19-

http://archive.a7ca.org/wp-content/uploa..._1400D.pdf

Section through the Big Seven Engine- Page 17- 

http://archive.a7ca.org/wp-content/uploa...7_1523.pdf

And the Austin Eight-

Nate - if it's any help to your question, you'll find claims that the Big Seven and Eight engines were different, but there really isn't a great variation.  Certainly, as said, the Seven engines were totally different and I can't think of anything much that's interchangeable if that waa your thought.  Good Luck, Cheers,  Bill