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Guys -

I have a 1970 429 block that is supposed to be 429 CJ, but it has only 2 bolt mains. Was it in '71 that 4 bolt mains came into play - and if so, how can I tell for sure what the block is?

Or did the DOOE heads and intake make the block a SJ n 70?

Thanks!
 

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Hi Rodney,

You are right that the 1970 429 CJ had two bolt mains and the 1971 429 CJ came with the 4 bolts mains. Yes I would look at the heads and the intake. The 429 CJ ports measure 2.12 x 2.86 inch on the intake side vs. 1.85 x 2.56 for the standard 429.

All the best,
 

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Yep. ^
Get the casting number off the block and decode it, since that's a much better indication of what you really have.
 

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