It seems everyday all-day my head is filled with various aspects of my build.
I have some questions that I have not found definitive answer to , as well, these questions run off into tangents leading to more questions.
I still have lots of numbers/measurements to crunch but I feel these questions would give me a better realization of my goals as a combination.


Fire Rings & Bore Size

If I am understanding things correctly the benefit of a large fire ring on a head gasket means the ability to unshroud the valves more.
This leaves a space (the thickness of the gasket) between the block and head around the bore in the space where there is no valve unshrouding.
My question- If the piston TDC is above the block are the forces on the side of the piston from the combustion event a problem?

How close does the head gasket need to be to the edge of the cylinder bore?

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<img src="http://farm4.static.flickr.com/3173/2992308402_5481afb26e_t.jpg">

The fire ring needs to clear the cylinder bores and notches and not stick into the bore. Larger fire rings are for larger bores. If you notch the bores to unshroud the valves the fire ring may need to be larger. You cannot use a larger fire ring to unshroud the valves. The fire ring doesn't have to be very close to the bore, but having it far from the bore increases crevice volume and unburned hydrocarbons. The crevice volume between the block and head often becomes filled with carbon. My 273 looks kinda silly with 4.08" bore head gaskets, but it doesn't hurt anything.

Positive deck pistons are unaffected by combustion pressure. Imagine squeezing a disc around it's periphery. Detonation or preignition typically torches down the side of the piston or blows a hole through the thinnest and hottest portion of the piston crown.

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Joshua