440 Marine Intake and Exhaust

You may want to check that intake for cracks. It's a real problem with those manifolds. So far, I've found 4 good ones in the 200 or so I've magged in the last 40 years. The main problem area is the thin webbing between the secondary barrels. The crack starts there and eventually goes down through the floor. Another area that is fairly common is the EGR port. Yours looks blocked off, so, it may be ok there, but, I would pull that plate and check anyway. Those heat exchangers can be a real problem with corrosion, especially if they've been run with salt water. Good Luck!