Once the exterior polishing of the engine block was complete, I started looking on the internet for other little hot-rodding tips to gain a few extra horsepower here and there. From the internet:
“Because of the Northstar's lower crank case design, each main bearing bulkhead comes down almost to, if not touching the surface of the oil, essentially sealing off each bay from its neighbours, dramatically increasing pumping losses. GM found that holes in the main bearing bulkheads to allow each bay to exchange air with its neighbours were practically a necessity. In testing otherwise identical prototype engines, it was found that engines without windows gave up 30+ HP to engines with windows.”
There are two different sets of windows; small U-shaped ones on either side of each main crank bearing web, and much larger circular ones where the camshaft would normally reside if this were a cam-in-block engine design. The problem is that these window passages have sharp edges that don’t optimize the flow of air through them. A simple hotrodding trick to squeeze a few more ponies out of a Northstar is to break the sharp edges to allow a smoother airflow. I found that a high speed burr in my pneumatic die grinder made quick work of this:
“Because of the Northstar's lower crank case design, each main bearing bulkhead comes down almost to, if not touching the surface of the oil, essentially sealing off each bay from its neighbours, dramatically increasing pumping losses. GM found that holes in the main bearing bulkheads to allow each bay to exchange air with its neighbours were practically a necessity. In testing otherwise identical prototype engines, it was found that engines without windows gave up 30+ HP to engines with windows.”
There are two different sets of windows; small U-shaped ones on either side of each main crank bearing web, and much larger circular ones where the camshaft would normally reside if this were a cam-in-block engine design. The problem is that these window passages have sharp edges that don’t optimize the flow of air through them. A simple hotrodding trick to squeeze a few more ponies out of a Northstar is to break the sharp edges to allow a smoother airflow. I found that a high speed burr in my pneumatic die grinder made quick work of this:
The photo below shows the larger circular windows. They were a little awkward to do because the adjacent webbings got in the way:
Lastly, in my search for any other little improvements, I found casting flash in all of the oil passages around the main bearing bolts. It wasn’t serious, but clearly an impediment to the oil flow up to the main bearings. Here’s a general picture showing where I found this problem:
And here’s a close up view of the casting flash. This passage was the worst one but all of them had some to one degree or another:
A one-second twirl of a little router bit in the Dremel took care of the offending metal. This is before I cleaned it up with a bit of sandpaper: