If If I change the quench what really happens

I might end up changing the quench height on a build.. what really happens to
the performance on a street engine.. I might have to go from .039 to like .080 so
my exhaust valve will get proper clearance(other than compression)

less quench slows the flame front

So I just advance timing to help the slow front

It might require less timing to prevent detonation. Ages ago I had some friends who both had very similar 360s. One was 10.5:1 with KB pistons and quench was paid attention to. The the other was 9:1 no attention paid to quench. The quench engine was almost a full second faster and could run more timing than the lower compression engine.

The mixture in the quench volume will burn, but it may burn too quickly.

Good to know.. right now I need to check the exhaust pocket depth to see if I can mill them deeper
and still have enough material in there before I can make any decisions.. might be easier to get
some other pistons if cheap enough.. I will sonic check them in a day or so

Mike,
In my opinion the engine will be more prone to detonation with that much clearance.
Bill

Could you maybe find a ex valve with a hair thinner margin and cut the piston a tiny bit like you mentioned?

Just a thought, if you have a wide margin on your ex valve, couldnt you flat off .010 without issue, I know some of the ferrea valves I use have a very very thick margin that could give some room if needed.

Deckaids ago i used a cutter that you put in place of the valve , secure the head to the motor with a couple of bolts and use a drill to cut each piston. It made a mess but grease in the crevice of each piston/ cylinder wall allowed me to clean it up fine. Wow, that must have been 45 years ago now. Crane or Comp or Isky had the cutter, can't recall who.

I did the same thing years ago but this engine is still on a stand and I can pull the pistons
to put on the mill

that's what I did, I cut an old cyl head into thirds & got an intake & ex valve that were .100" larger than the valves & glued sandpaper to the faces & used a drill. I put tape around the perimeter on the piston to contain the debris & had the piston at TDC. worked perfect

Isky still has them.

Isky Valve Pocket Cutter

How much would a high swirl high velocity port help?

It seems high swirl and high velocity don't matter much after all, they got 330 CFM sewer pipe heads on 345 CID truck engines now and they don't lack any TQ...

The term "High velocity heads" just means the heads don't flow enough

Mike,
Years ago I had a 340 my Dad put together for me in a duster. It had 10:1 with very little quench. It would knock like crazy on pump gas.

Shortly after being put together, it ate a flat tappet cam, and all of the metal went in the pistons. Rebuild the motor with another set of flattops, but this time at 12:1 with very tight quench (.035"). That motor would run on 93 octane ALL DAY....

So I'm not sure what your plan is, but I was able to raise compression almost 2 full points, AND have it run better on 93.

I havent been out in the shop to do some measurement but I have thought about new pistons

I'm convinced!