Packard Forum Index » Modification Discussion

I found a head gasket on ebay that was reasonably priced. The thickness of the gasket is .100. Does anyone know what the compressed thickness is going to be? As I am planning out my 356 build, increasing compression is high on the list. With that in mind, the phenomenon of quench is one of the methods used to allow more compression without detonation. Quench is the distance between the top of the piston and the flat area of the head. The piston comes very close to the quench area of the head squeezing the air/fuel into the combustion chamber. If you can imagine stepping in a shallow puddle and the water sprays out from under your shoe. It has been found quench is nearly non-effective above .060" distance. .040" is pretty common target for suitable quench with a decent safety factor. Tightening the quench has provided improved performance, until the piston makes contact with the head, which is a problem. Building the 356, I'd like to target .035-.040 quench. If the available gaskets are .100 thick and don't compress much or any further, then I will have to spec a piston that tops out .060" above the deck surface to achieve the desired quench distance. If that makes the compression to high with an early 288 head, then I might have to use a stepped piston.
This is going to be a fun project. ARP has already mentioned $1000+ for a set of custom rod bolts. Not quite sure I need them as I'm not trying for high rpm, but new/better rod bolts would help to reduce worrying about it.

Mark

If I am recalling correctly, you can't go above the block with the piston stroke as the combustion chamber does not completely cover the bore and relying on the gasket thickness to provide the space is very risky at best. Remember that these were low-revving high torque engines where horsepower was more or less secondary.

Hi Don,
The goal is to get the piston closer to the flat area of the cylinder head, not into the combustion chamber.

Mark