big block engine code deciphering

[SH69Z28]

In my swapping to procure parts for my 69Z I ended up with a big block but don't know what the code means. Hope someone can help. Casting number is 3955272, has two-bolt mains, casting date is April 24, 1969, front pad stamp is TO428YO. Thanks.

[bertfam]

Are you sure it's not YQ? I don't show a YO in any of my books, but YQ is a 1969 20 or 30 series Truck 396/310. The 3955272 block was only used in 1969 so that fits.

Ed

[SH69Z28]

Thanks. It very well might be a "Q" since the bottom part of the character is very faint. Also cast into the block near the oil filter and under the bell housing is "Pass High Perf". There appear to be oil fittings possibly for a remote cooler. Is this block cast any differently than the ones used in the cars?

[bertfam]

No, all 3955272 blocks were the same no matter if they were destined for passenger cars or trucks. Also, all big blocks have "Pass High Perf" cast into them! Not sure why. Maybe John can shed more light on this.

Are you sure it's a two bolt main? Here are two pictures showing the difference between the two and four bolt blocks. Note the hole sizes.

Ed

[SH69Z28]

It's a 2-bolt block like the picture you sent. BTW here's a picture I just took. What looks like a crack near the middle oil hole is actually just a cob web. Thanks for all the knowledge and support this site provides!