302 block numbers clarification

[hotz]

Hello,
I just need some clarification on numbers for a 302. I know that chevy made a number of blocks for a 302 in 69. I thought the block number 3932386 was made from sept to dec of 68 for 69 car. Then chevy changed the block numbers to the 3956618 from dec to april or so. Finally in april or so they changed the block numbers to 3970010. Is this correct and does anybody know why chevy changed the block numbers so often?? Also where does the 3932388 block come? Final question is would a car made in oct of 68 have a 618 block? Thanks a ton

[jdv69z]

My Oct 68 10B Z has block 3932386.

Jimmy V

[KurtS]

Simple, design of the block changed and the block # changed to track it.

The block useages overlapped.
The 388 block is an early block.

[hotz]

Thanks for the help!!!! Are the production months for the blocks correct (sept-dec) (dec-april) (april- to end)?

[Hot302]

I have a 3932388 block with a date code of K 30 8 (Nov.30,68) if that helps any.

[GaryL]

Simple, design of the block changed and the block # changed to track it.........

What were the design changes?

[68Zproject]

Look in Colvin's BTN and it shows the blue print designs and changes for each block and will explain them as well.

[JohnZ]

Simple, design of the block changed and the block # changed to track it.........

What were the design changes?

Most were minor changes in water jackets, bulkhead contours/thicknesses, etc. - not externally-visible, and almost always backward-compatible.There were hundreds of minor changes in the basic block from '55 into the 80's, virtually none of which affected any of the bolt-on parts until the one-piece rear seal was introduced in 1986.