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Quote:

Originally Posted by adk61 (Post 4273361)

quench/squish supports combustion process by squeezing the charge into the chamber where the spark occurs, also has a cooling effect as the quench area runs cooler than the rest of the combustion area... this will allow for a higher compression ratio to be used and aid in the quality of combustion achieved... properly designed quench is like upping the octane, promotes a better burn!!

I know the textbook answer. :D

But why tighter than the recommended safe clearance?

Some say that for very tight quench we want the piston to "just about" kiss the cylinder head surface, but others say that there are diminishing returns or even the chance of promoting detonation (especially in power adder applications... blowers, N2O). Some very well known builders go so far as to say that tightening the quench below .050 on a BBC is a waste of time.

FYI I'm running .060 on my 1100sc engines

Quote:

Originally Posted by TomZ (Post 4273342)

Less than the minimum? If so, can you elaborate on why? Mine at .044 is still considered tight. Books and articles I've read on this subject say that the tighter than the minimum isn't necessary. Just trying to understand is all.

To answer your question honestly it was where the piston ended up. .001 in the hole with .041 gasket. When the motor was tore down you could see on the quench pad that the fuel mixture was being pushed into the chamber (very little carbon). I've ran a 496 in the past .005 out of the hole with a .039 gasket with no issues and that was a good running motor. If I was building a motor with a 4" stroke I would tighten the quench with a 4.750 stroke and a 4.600 piston with 1.120CH height there is alot of piston rock and makes me a little nervous tightening things up.

This is an older thread with some great information by Haxby.

http://www.offshoreonly.com/forums/g...ch-thread.html