Big Block heads are a find.  Buick made numerous different sets throughout the years.  Some of these heads flowed better than others.  Identifying heads (engine size and year), however, can be a difficult job.  This chart will help by providing you with casting numbers so you can determine what you've got, or know what to look for at your local parts yards.

Heads in Bold are "Big Port" heads.  These flow about 5% better than regular heads.  

What Heads Flow the Best?  
Through the years, Buick made numerous sets of heads for the 400, 430 and 455 engines.  These heads are largely interchangably.  Generally, the rule is that early heads can be used on later blocks but later heads will not fit early blocks.  I can't say that this is true, however, later heads (certainly 72 and after) came with larger chambers (for reduced compression engines) and various smog and emissions modifications.  So, from a performance standpoint, most people will want to use 71 and earlier heads.  The question is what heads flow the best.  The following is a list of the stock factory non-stage heads that flowed the best.

NOTE:  If using earlier heads on a later block (67-69 heads on a 71 or later 455 Block), you need to block the upper front oil passage hole (located beside the upper front head bolt hole) on the drivers side of the block.  If left unplugged, serious oil leakage will result when 455 rocker shafts are used.

1.    67-68 400-430 "Big Port" Heads (These heads flow about 5% better due to
       larger intake ports).
2.    70-71 455 Heads
3.    69 430 Heads
4.    72-74 455 Heads
5.    75-76 455 Heads

 The information listed above does not include porting.  Ported heads will obviously flow better than any non-ported heads.  Good port jobs, however, are EXPENSIVE.  The list is intended to identify the best flowing heads for people who don't have the bucks to port their heads.  My suggestion is to take a set of the 67-68 Big Port 430 heads and cut them for stage 1 valves, back cut the valves, match the intake manifold ports to the intake ports of the head.  If funds permit, then go a little further and unshroud the area around the new big valves in the combustion chamber, and polish the combustion chambers.

Big Block Performance Heads Tips 

• Block Exhaust Crossover
  Install cap plugs (2 per head) to block off the crossover passages. If you remove your cylinder heads, the better course of action is to have a quality head shop fill these passages flush to the exhaust port. This keeps hot exhaust gases out of the intake manifold giving you a denser and cooler air/fuel mixture and equalizing the exhaust port flow by eliminating turbulence in the 2 center exhaust ports.




• Back Cutting Valves
  Stock valves restrict the air flow into and out of the head.  Back cutting the valves 28 to 30 degrees is a huge bang for the buck on any Buick, big or small block.  Back cutting will enhance low and mid lift flow numbers. 




• Intake Port Matching
  Ideally, intake manifold port openings and cylinder head port openings should match perfectly.  Match porting will help achieve this. One thing to remember, a perfect match is almost impossible to attain, so it is better that the intake manifold openings be slightly smaller than the cylinder head port openings.  UNDER NO CIRCUMSTANCES do you want the intake port opening larger than the head port.  This will cause turbulence and reduce air flow, thereby hampering performance. 




• Exhaust Port Matching
  If using stock exhaust manifolds, match porting the head exhaust openings to the exhaust manifold openings will benefit performance.  DO NOT enlarge the exhaust port flange on a Stage 1 head.  The manifold needs to be larger than the head port to prevent or reduce exhaust gas reversion.




• Unshrouding Valves in Combustion Chambers
  If you install Stage 1 valves in a standard small valve head, you MUST relieve the combustion chambers around the valves.  If you do not, you will most likely not increase airflow or horsepower.  In fact, air flow reduction may occur. 



• Polishing Combustion Chambers
  This is beneficial not only for race engines, but for street driven engines too. Polishing will remove sharp edges that could cause hot spots in the chamber and result in early detonation.