[72LuxuryLeMansLa.]

Originally Posted by lust4speed

With all the talk about how important quench is, I'm surprised to see the deck of the chamber opposite the sparkplug laid back so far.

I was thinking the same thing. There would be very little quench with these heads. I wouldn't want to use these. But I'm certainly no expert.

[lust4speed]

Maybe quench isn't as important as it is puffed up to be?

I don't believe that the old hemi-heads had any quench area either. In the past before the D-shaped dished piston we ran full dished pistons that had little to no quench, and they still ran very hard. I remember reading that you either wanted a tight quench area under .050" or an open area with at least .100" clearance to avoid detonation.

[Will]

Originally Posted by lust4speed

...I remember reading that you either wanted a tight quench area under .050" or an open area with at least .100" clearance to avoid detonation.

I think this is the key. If you have a quench area, it needs to be a tight clearance to avoid not getting things mixed well in the chamber.

Having a very minimal quench area is probably not that big of a deal compared to having too much clearance between piston & head in a larger quench area.

Also consider, this chamber design is almost 50 years old. Modern chamber designs are undeniably more efficient and most include significant quench area.

Still, as mentioned, the 061 chamber is very similar to the round port head chambers, so they may have had some advantage. Sure wish we could talk to the guys who designed this stuff.

The engine those heads were on (440") ran great and didn't need more than 32 degrees timing.

[steve25]

The quench area is very important on a parallel valve wedge type chamber that our heads have in terms of complete burn and speeding up the burn rate, and the 061 casting is the last Pontiac casting on earth that I myself would plop on a motor regardless of air flow differences just due to its lack of quench!
The differences in valve angle in the head castings in easy to tell.
Other than any of the 60s SUPER DUTY heads, only Pontiac heads with push rod guide plates will be of latter 14 degree valve angle, all others will be the early to mid 1967 20 degree valve angle type.
The 670 casting and its RA1 factory mod with taller valves and springs that is re-stamped 997 are the only 14 degree valve angle heads with a closed chamber.
This chamber is slightly different than the early wedge chamber heads on the Intake valve side.

[BruceWilkie]

Originally Posted by lust4speed

With all the talk about how important quench is, I'm surprised to see the deck of the chamber opposite the sparkplug laid back so far.

Better suited for boosted motor IMO. Greater charge density and pressure kind of does what quench does for NA. Not uncommon for boosted motors to have the pistons .100 or more below deck. Heavy N2O uses softened chambers as well.