454 block #3963512 dated "A 4 71".. i need more information


New Member
Oct 19, 2012
1969 chevy camaro
Hello... i am new here...

i was wondering if someone can help me in this issue...

i found a 454 chevy engine that has been putted for sale... the block casting number stamped on the bellhousing is #3963512 dated "A 4 71"... i need to know more information about this engine before buying it because as i've been told, it's a rare block...

i looked around the internet and i found that this block may have around 365hp to 425hp... but nothing can affirms the exact hp.. and i didn't find anything that can help me regarding the date stamp "A 4 71"... i mean sure it's a 1971 block but i am looking for more information...like is it 2 or 4 bolt main?? exact hp?? is it really a rare and valuable block?

the person who are selling the engine don't know if it's a ls5 or ls6, 2 or 4 main bolt and he don't want to open the pan to check it..

i reaaaaaaaaaaaaaaaaaally appreciate any help :(...

thanks guys..


Staff member
Oct 7, 2012
1976 Chevy Cheyenne 1500 P/U
Re: 454 block #3963512 dated "A 4 71".. i need more informat

Well, from the Engine Casting Number and Date Code you have, we can tell;
Engine Casting Number - 3963512 - This engine was manufactured from 1969 to 1971, as either a 427 or 454 COPO (see note below).
Date Code - A 4 71 - A = January, 4 = fourth day (of January), 71 = 1971.

So, from the numbers you have there is a possibility this engine is desirable to have.
But, rare, maybe so, maybe not.
Beauty (and price) are in the eye of the beholder.
What is really needed to identify the engine is, the Partial Engine VIN Number and the Engine Assembly Code.
These numbers would be stamped on the block, usually stamped into the pad on the front passenger side of the block and would look something like this;
Engine Assembly Code - V0112CLJ
Partial Engine VIN - 13N132794
Interestingly, Chevy began in 1970 - 1971, moving these identifying stampings to different areas of the engine.
It may be necessary to scrape off paint, grease and dirt to see these numbers.

Note - COPO - "The COPO system (Central Office Purchase Order) was truly intended for more mundane fleet type of alterations.The most common use of the COPO system, was to specify fleet paint schemes for municipal vehicles, heavy duty springs and special fabrics for use in taxicabs and the like. The Central Office Purchase Order (COPO) is legendary for creating rare, super secret, high performance Camaros. The COPO System was never intended for creating ultra high performance Chevrolet vehicles, but try telling that to the likes of Don Yenko, Baldwin-Motion, and Berger Chevrolet. Don Yenko of Canonsburg, Pennsylvania, is largely credited with being the first to exploit Chevy’s COPO system. Exploiting it, is probably not the right term to use here, Yenko simply build Chevrolets the way he thought they should have been built all along, more powerful." (excerpted from Classic Chevys).

I am hopeful some of this is helpful.
If you can get the other numbers from the engine, post them and I'll try to help make some sense of them for you.

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