How large of dish in Piston?

How large of a dish can you put in a piston to lower a Compression Ratio without it screwing up the quench on the Heads?

EX: 4.5 Stroke and 4.5 Bore. Lower it to run on pump gas? 72 CC heads and a .042 gasket.

Thanks Tore

Depends entirely on what piston you're talking about. Some you can get pretty deep, some you can't cut at all.

Tore,
I think I understand your question, and it's at what thickness, do we destroy the quench effect. I'm not for sure that anyone has come up with a magical number, but I believe that by the time your somewhere around .080" to .100" in thickness, that you have "killed" your quench and you might as well not have it.

If you need to lower the compression and put a dish in a piston,,,and while playing attention to what Mark was referring to in regards to the head/crown thickness of the piston,,,it would be best if your piston dish shape was a mirror image of your chamber. Say for example, if you are using P-51 heads with a figure 8 shaped chamber,,,then use that same figure 8 shape on the top of your piston crown and have it in the same location. Your trying to get the perimeter of the dish to mate up with the perimeter of the chamber, like two halves of a clam shell.

Hope this helps,
Charlie

Charlie you hit the nail on the head. Thanks for the info.


Thanks Tore

didn't say what C/R wanting . miirrior image of a small surface area means a deeper dish . the depth of dish limit will be set by the CH

Right around 11 to 1 comp. Something that could run on 93 octane gas.



Tore

Tore with a 72 cc chamber you will need about a 35 cc dish and depending on the head used it will be some where between .150 and .200 deep This is just an educated (or uneducated) guess.

The normal rebuilder piston is around 19-21 cc If I remember right, so that should give you some idea.

The more narrow you have the dish, exhaust manifold to intake manifold the better your quench will be. But like Charlie said try to keep it close to the shape of your Chamber for best results.

This is a estimated answer, you need to talk to a piston manufacturer to get the exact dimensions.

The heads are some TFS Street Heads with the normal shape combustion chamber.