I am being told that a 1967 327 with the same casting code as a 1967 350 (3892657) can be allign bored to allow the larger journal 350 crank to fit and this is all that GM did to the blocks in the factory.... The main caps are also all the same...
Cost to allign bore is about $400... 327 blocks with that code are much easier to locate...
What are your thoughts/understanding???
The main bearing locating tangs are a different size and in a different location on small journal and large journal blocks.
I recently did a side by side comparison of two 1967 Camaro “657” blocks. One was a 350 large journal and the other a 327 small journal. The most interesting thing I found was that both of the 657 blocks had been machined to accept both small and large journal main bearing tangs. As far as I know this is unique to 657 blocks. The large journal tangs already in place makes it possible to line bore a 657 small journal block out to large journal size.
Another difference is the machining of the face behind the front thrust surface of the rear main bearing. The face is machined slightly larger on the 350 block to accommodate the larger diameter thrust surface of the large journal rear main bearing. You may have some interference with the outer edge of the large journal bearing thrust surface with the small journal block. This could be easily fixed by machining a small amount (.020”) from the edge (not the face) of the rear main bearing thrust surfaces.
Also the bore on the rear main saddle and cap is beveled so the sharp corners won’t dig into the rear main bearing. Boring it out will remove the bevels so new bevels will need to be cut.
The last difference is the groove for the crank oil slinger is machined larger on the 350 block. The groove in the 327 block little too small for the 350 crankshaft slinger. The easiest solution would be to turn down the slinger on the 350 crank.
Here are some pictures for further clarification: http://firstname.lastname@example.org/Team_Camaro/3892657/