A water jacket fill to the bottom of the freeze plugs would be a good idea. The factory crank will handle that power level with no issues. I’d suggest ARP main studs. It would be a good idea to have the dowel holes on the main caps resized to 5/16” diameter and the line bore hones by a competent shop. Use longer dowels that engage to full length of the hole with either stock dowel diameter or oversized. With the stock stroke those are the main performance mods for a stock 3.75” stroke. Those are good mods for running 500 HP in the weaker blocks with the stock stroke.

I do have halo’s and a main girdle to reinforce the main caps for added strength. It shims the oil pan down .25” and is for use with aftermarket Canton and Milodon oil pans. Designed for 500 HP and up with larger cranks.

Hi Jay. I just acquired a 557 block 400 pontiac and was looking for info on what I needed for a performance build and saw you talking about what you did with yours. I've never worked on a pontiac, but have built a few others in the past. You mentioned halo bars or something along that for tying in the main caps. Do you have pictures or some description of what you are referring too? My goal is about 500 to 525 hp and was thinking about keeping the stock stroke. Is the crank strong enough for that? I plan on going in on some edelbrock or Kauffman heads. This would be a mostly strip car, little street. What about hard block? Maybe 1/4th fill.