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Old 06-14-2019, 04:57 PM   #1
badass68
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Default LS turbo Quench area

Putting together a new motor with a 3.75" stroke. I can custom order, or buy shelf pistons for a 3.8" stroke which would put them in the hole .025". That'd give me .075" quench. Is there anything wrong with that if my compression is where I want it?
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Old Yesterday, 01:02 PM   #2
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Default Re: LS turbo Quench area

Nothing wrong with that at all. Just be aware that a large quench distance is not the same as a softened chamber or parabolic piston dish as far as detonation goes. Not saying you need to be concerned about it since I don't know the details of the application. Hope this helps.
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Old Yesterday, 01:55 PM   #3
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Default Re: LS turbo Quench area

Will the larger quench promote detonation?

LS3 390ci
10:1
63cc heads
flat top
E85
25psi max

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Old Yesterday, 02:26 PM   #4
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Default Re: LS turbo Quench area

No. Small quench is worse. The real cause or at least a contributing factor is parallel surfaces like piston top and quench pad in the chambers. It has to do with reflected pressure wave and/or very dense mixture causing a localized high pressure spike that is enough to set off the mixture in these areas which starts a chain reaction of sorts. Also the shallower the valve angle in the combustion chamber becomes very thin if you look at a cross section which promotes a very rapid combustion event. This is great for NA or low boost production engines as it is more efficient and less emissions but bad for big power production. Basically the closer you can get to a Gen2 Hemi chamber the better. This is the primary reason the hemi has been the king of boost for over 5 decades. That big, slow, curved chamber with even pressure distribution low swirl and true cross flow design is nearly perfect in every way when it comes to making big power with big boost.
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Old Yesterday, 02:51 PM   #5
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Awesome! Thank you for the detailed explanation. Using the shelf pistons will save me some time and $. 👍🏻
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Old Today, 08:50 AM   #6
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Default Re: LS turbo Quench area

There is some info out there that suggests quench clearance up to around .065/.070" is fine, but then there is a quench clearance of between .070" and .120" where combustion efficiency falls off and this may promote detonation,poor flame propagation etc. Once you get over the .120" quench clearance figure -then basically you don't have any quench.
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Old Today, 11:01 AM   #7
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Oh. Well that’s not good because depending on head gasket choice, I’d be .075 or .085.
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