two bolt BB vs four bolt

[302moz]

How can you tell the difference in a real four bolt block (1969 512 )from a two changed to a four?the oil cooler and oil pressure holes are bigger in a four ,but are easy to change. Any other ways to know for sure its a real four bolt???thanks John any pictures would be very helpful

[ssl78]

They always do not put in the valve relief in the cylinder

[302moz]

thanks for the info John. Any other things?Are the outer holes for the for bolt caps counter sunk?

[bbbentley]

I recall this Youtube video tutorial you need to watch: https://www.youtube.com/watch?v=tlizhIURezE

[302moz]

great video.Thanks for the info

[the427king]

"They always do not put in the valve relief in the cylinder".......John, you are right on the valve reliefs . He also left out 3-4 more signs,with one being the tell all , especially for such a long video . Seemed to focus too much on the line hone,which is really ireelvant in that most blocks get that regardless if they are converted or not.

[302moz]

so what are the 3 or 4 more signs?thanks

[69L72RS]

I know of at least three builders who broach cut the caps and use a vibratory method to "seat" the caps to the blocks, prior to honing, so that is not a guarantee.
Just my $.02.

[Zman1969]

I thought the oil plugs along the side of the block were a little larger on the 4 bolts - IIRC
?
that and the 1" oil plug on the side - I know now that the later 4 bolts are not made that way anymore maybe because the oil filter adapter coolers that became avail in the '80s? I have a 90 or so LS6 454 4 bolt crate engine that doesn't have the big plug

[VintageMusclecar]

The later blocks (I have a "445" block) aren't drilled for the large hole since the trucks they came in usually had an aux. oil cooler adapter sandwiched in between the block and the oil filter. There was no longer a need to drill the block for the larger fitting.