Quench? Enlighten me Guys.....

[PinkE]

OK...I've been reading a lot about quench, I know it's the area between the top of the piston and the head...But what I don't know is how you measure it, attain it, and what exactly is good or bad quench.  Maybe someone (or a few of you) could explain it a little better.  I think the lower the number the better it is... to a point...And this is the area where detonation occurs, a smaller area would make a stronger detonation of the fuel, and a larger area would make a less powerful detonation.  And also I was wondering how a blower would affect this quench....

Just a girl trying to understand things... ...

Sue

[Bigcube]

OK, I'll see if I can splaine it to you  You are correct, it's the area between the top of the piston and the closed face of the heads.  .040 is safe for steel rods, alum you should stay .060 cause the rods can strech at higher rpm.  The problem with being too close is contact, you don't want the piston kissing the head... that's bad. Given you have a closed chamber head, it can be measured by measuring the top of the piston height at the top of the stroke relative to the deck of the block, then you just add in the gasket thickness. For example suppose the piston in .010" "in the hole" meaning the top of the piston is .010" down from the deck of the block. then you add in your head gasket thickness of say .040", then you have .050" of quench.  There are some pistons made to do this kind of thing with open chamber heads.  As far as how a blower works, it just packs more air and fuel in there... the quench is a measured distance.  HTH's

[PinkE]

OK, well a lot of pistons aren't flat, there domed, so would you measure the highest point?  And if it's domed would you get an accurate measurement?  What about all the space beneath the top of the dome? 

Thanks for the answer Jim...

[Bigcube]

The domed part fits into the combustion chamber of the head, it's there to build compression.  The detonation occurs easier if the quech distance is too wide, that allows for more fuel and ais to squeeze into that dead space.  It's measured the same way with domed pistons, the concern is the distance between the flat part of the piston and the closed portion of the head.  Last year I had to order .050' gaskets to replace the .043" I had planned on using because my brand new block was shorter deck height than I ordered.  I was looking for a tad over .060" quench and I was sitting at .056"  Too close for comfort for me. 

[BLOWNZOOM440]

good morning PINKE!part of the reason for quench is to push the fuel mixture to 1 area where the spark starts.the pressure buildup from the flame going to the other side of the piston can over heat the mix from pressure reaching a temperature more than the fuel can take and it pre ingnites.so when the mix is confined to 1 side it dose not have that chance.

[PinkE]

OK...I think that Splains it pretty good guys...I've been enlightened on that subject....But I'm sure I'll think of another topic soon...

Thanks Guys....

Sue

[PinkE]

OK Jim, another question... ...You siad you had to use a thicker head gasket to get more Quench and make sure the piston didn't hit the head...Doesn't this make it easier to blow a head gasket?  Isn't having a thicker one make it more vulnerable to blowing?  I would think with the power your pushing out of that motor you'd want things pretty tight there....Maybe this is a dumb question too? 

[Bigcube]

I run copper gaskets and the block is O-ringed and I also have a matching receiver groove cut into the heads. They match the o-ring in the block.  No worries of blown headgaskets   

[PinkE]

Gotcha....Nuff Splaining for one day...I was just worried.... ...But it seems like you've done your homework....

[Bigcube]

Thanks for looking out for me Sue