If you are a purveyor of performance with a turbocharged Buick V6, boy do we have some parts for you today! These Buick Stage II V6 heads are NOS, never used, and killer horsepower makers. We’re not sure what the current aftermarket offerings are for that engine but we do know that these things were used to make 520+ naturally aspirated horsepower and beat up on V8s when NASCAR allowed them to be run at their events. These heads have never been mounted to an engine, they are in perfect as-shipped shape.

We’ve never seen these heads box stock and never so much as having valves in them before. How good are they? We’ll let the experts tell you.

Here’s some awesome stuff we found that comes from a NASCAR Grand National engine builder back in the day with respect to these heads:

According to Ruggles, “The key to making horsepower is the cylinder head. That’s true with any engine. The Buick V6 has a hell of an advantage because the Stage II aluminum cylinder head (#25500030) is the best wedge design I’ve ever seen. We port the heads, do a three-angle valve job, and install Howard Stewart (2.02-inch intake and 1.625-inch exhaust) titanium valves along with the proper valve springs and retainers for the cam we’re using. The porting is pretty straightforward, there’s nothing tricky because the port is the right shape to begin with.

“In addition to air flow advantages, this cylinder head (with an as-cast combustion chamber volume of 44cc) also permits compression ratios in excess of 13:1 with flat-top pistons. In our testing, we’ve found that the old V8 rules about connecting rod length are meaningless. Traditional rod/stroke ratio guidelines simply do not apply to a Buick V6 because the piston dome has been elimi- nated. With a Buick V6, rod length appears to have absolutely no effect on the horsepower curve. But since an increase in rod length reduces cylinder wall side loading, we use the longest practical center-to-center length, which is 6.500-inches.”

Another departure from V8 guidelines comes in the area of fuel octane and spark advance. It’s possible to run extremely high compression ratios with a Buick V6 without having to resort to exotic, maximum-octane gasoline. So long as a good quality racing gasoline is delivered to the carburetor in adequate volume, detonation will not be a problem. The combination of a flat-top piston and high-swirl combustion chamber reduces octane requirements as compared to engines with high-domed pistons. With the Stage II’s small, high-swirl, fast-burn combustion chamber, the flame front travels quickly and efficiently, so detonation rarely rears its ugly head. Testimony to the efficiency of the Stage II combustion chamber is the conservative ignition timing used with these engines. Even though the spark plug isn’t in the exact center of the cylinder, Ruggles specifies only 34° of advance for virtually all his race engines. Hemi-head engines with centrally located spark plugs require approximately the same amount of advance.

eBay: These Buick Stage II V6 heads are NOS, never used, and killer horsepower makers