Quench...

dave brode

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JM/All,
Neat stuff, huh?

War story:

1. my daily beater is a thrashed '95 S-10 with a 2.2. It always pinged, esp at part throttle. I freshened the engine at 170K or so. The quench distance was .078" or so. I hacked the block and aimed for .038". Then I saw the pistons were all loose on the pins. The bores looked good, and I'm a cheap sob, so I bought new std bore pistons. They were .010" shorter. I had already bolted the crank/cam etc in the engine, so I let it go, rather than hack .010" more from the block. Even at a .048" assembled quench distance, it pings less now than it did when quench was .078", even though the compession ratio is higher now. 
Dave
 

dave brode

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Stampie,

I'd go .002", fwiw. You might ask Shawn what he ran the clearance in his last engine though. The skirts on them look like new.
Dave


link=topic=1082.msg11006#msg11006 date=1112379048]
I was looking at the http://racingarticles.com/article_racing-10.html link and it mentioned piston to bore on the KB's.  Should I go for a tight .0015 clearance with my KBs?  I'm with Terry and there won't be any funny gas on this engine.  Static CR will be around 10.25 with a .030 quench.

Thanks,
Stampie
 
A

Anonymous

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When I took auto shop in high school (Back when the Dead Sea was just sick & Pterodactyls still ruled the sky) I remember reading about a subject that was being called "Quench".

At that time the word was used to describe what happens when the atomized fuel came in contact with the cool combustion chamber & cylinder walls. The cooling effect was supposed to cause the fuel to condense & be more difficult to ignite & burn. The auto manufactures where raising the coolant temps & operating the engine at a higher temp in an attempt to reduce the "Quench".

Anyone else remember this?

~JM~
 
A

Anonymous

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I think the machine shop did my KB 509 to .002-.0025 piston to wall clearance. I dont kemember exactly, but they were done EXACTLY to the KB specs that came with the pistons. A torque plate was used. The skirts looked like new when it was disassembled for inspection. The walls WILLl distort as much as .003 near the top of the bore without a torque plate. I witnessed it myself when the torque plate was removed and the bores were rechecked.  :eyepopping:  :yikes:  My point is.......................USE A TORQUE PLATE!!!!!!!!!    :D
 

dave brode

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JM,

Don't know about that. Could be. However, if you've read Riccardo's "The High Speed Internal Combustion Engine", you may agree that it has more to do with the size of the fuel droplets for out purposes. Afaik, more turbulence  = smaller droplets. The smaller droplets burn [from outside in] at a faster rate. Therefore, afaik, the cylinder pressure is higher, burn is faster, and less timing is needed. Interesting stuff.

On the subject, imo, a reeeaally wide quench distance is "ok", but not one that's between 60 and maybe 100 thou. Iirc, Potter said so too.

Look as Sean M's combo. Really wide quench distance due to short [1.615?] pistons and 7" rods, but it did ok. I would assume that his quench was at .100" or so. Imo, if the quench is really wide, the quench area just becomes part of the chamber. If it's say 60-80 or so, it's not tight enough to cause a good quench action, and it becomes a bad dead air sort of a thing.
Dave





~ link=topic=1082.msg11009#msg11009 date=1112381886]
When I took auto shop in high school (Back when the Dead Sea was just sick & Pterodactyls still ruled the sky) I remember reading about a subject that was being called "Quench".

At that time the word was used to describe what happens when the atomized fuel came in contact with the cool combustion chamber & cylinder walls. The cooling effect was supposed to cause the fuel to condense & be more difficult to ignite & burn. The auto manufactures where raising the coolant temps & operating the engine at a higher temp in an attempt to reduce the "Quench".

Anyone else remember this?

~JM~
 
A

Anonymous

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stampie said:
Do you have any piston slap sounds at that clearance?

Stampie
The motor was quiet. I would NOT go ANY tighter than .002 with the KB hyperutectics or you will start scuffing parts and possibly lock up the pistons in the bores. If its going to be driven on the street, .002-.025    If its a dragrace motor, .002-.0045 on gasoline. These are specs for KB hyper-pistons for a 4.100 bore and bigger. Did I mention to USE A TORQUE PLATE !!  :D   :thumbup:  :D      ;)
 
A

Anonymous

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I have both BHJ and a set of potters they seem to pull the same
Buy some studs for the plates if you intend to use studs on your engine
Rich's plates are pretty nice I just needed another set and found some cheap from a machine shop that had never used them and wanted em out of there
 

Sean

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dave brode said:
JM,



Look as Sean M's combo. Really wide quench distance due to short [1.615?] pistons and 7" rods, but it did ok. I would assume that his quench was at .100" or so. Imo, if the quench is really wide, the quench area just becomes part of the chamber. If it's say 60-80 or so, it's not tight enough to cause a good quench action, and it becomes a bad dead air sort of a thing.
Dave







The turbo engine was near the worst quench possible. But it may not be as big a deal on a blown engine. They supposedly have some turbulance regardless. The pistons were .058" +/-  in the hole so about .098" of quench.
 

dave brode

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Sean,
[bottom post]


link=topic=1082.msg11119#msg11119 date=1112478952]
dave brode said:
Look as Sean M's combo. Really wide quench distance due to short [1.615?] pistons and 7" rods, but it did ok. I would assume that his quench was at .100" or so. Imo, if the quench is really wide, the quench area just becomes part of the chamber. If it's say 60-80 or so, it's not tight enough to cause a good quench action, and it becomes a bad dead air sort of a thing.
Dave


The turbo engine was near the worst quench possible. But it may not be as big a deal on a blown engine. They supposedly have some turbulance regardless. The pistons were .058" +/-  in the hole so about .098" of quench.
I've always also thought that quench wasn't as important on a supercharged engine, but the Vizard piece that someone linked to the other day says otherwise, at least on that engine. I wonder if you could run a thick copper gasket or even two Cortecos back to back to make the quench up in the .140" -.150" range, and lower the CR too?


Fwiw - I remember the old Max-wedge mopars came from the factory with two stacked gaskets to lower the CR on them. The hot lick was to remove the doubles for more CR. Btw - a fellow that I know who is very learned on turbos who told me that he knows of many turbo's sb chevs running the pistons waaayy down the hole to lower the CR with small chambered heads.
Dave
 

Sean

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Its common for the turbo  SBF Pro and Outlaw type cars to run the pistons .100" to .200" in the hole. They run aluminum rods. Some guys swear you need a tight quench even on a blown engine on pump gas. I don't know either way for sure.
 

dave brode

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Sean,
Who knows, but I'd be inclined to make it tight, or over .125" or so. Maybe real wide would cause the quench area to just become part of the combustion space sorta.
Dave




link=topic=1082.msg11123#msg11123 date=1112480376]
Its common for the turbo  SBF Pro and Outlaw type cars to run the pistons .100" to .200" in the hole. They run aluminum rods. Some guys swear you need a tight quench even on a blown engine on pump gas. I don't know either way for sure.
 

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I don't know from nothing, but what I have gleaned over the years is that you either run a quench engine, with preferably around .040 piston to head clearance, or you run wide open, at least .200 so that the engine sees an "open" chamber.  What you have to be careful is not to be between .060 and .200 - if you are,  the engine will be very prone to detonation, and this was apparently the problem with the '72 thru '76 Cad engines, and maybe beyond.  Anyone care to shoot me down on this??

regards,  Bob
 

dave brode

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Bob,

No shoot-down, but the topic has been discussed here before, and at least some experts [I'm not one] claim 60-100 is the bad zone. I agree with you in that 200 would be safer. Let's see, an 82cc head on a flat top 514" with a .200" quench would be apx 9.0-1.
Dave


rowaid said:
I don't know from nothing, but what I have gleaned over the years is that you either run a quench engine, with preferably around .040 piston to head clearance, or you run wide open, at least .200 so that the engine sees an "open" chamber.  What you have to be careful is not to be between .060 and .200 - if you are,  the engine will be very prone to detonation, and this was apparently the problem with the '72 thru '76 Cad engines, and maybe beyond.  Anyone care to shoot me down on this??

regards,  Bob
 

Darius

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Quench and open chamber heads:

Air cooled engines run hotter than water cooled engines and are therefore more prone to detonation due to higher head temperatures. Years ago I turbocharged the crap out of various Corvair engines and found that the open chamber head that came stock on the later turbo engines (1965-66) were MORE detonation prone than the smaller (higher C/R) closed chamber heads of the earlier (1962-63) factory turbo motors. 

After experimenting with various head over many years if was clear that a tighter quench was very beneficial to turbo charged heads - even when higher compression ratios resulted.

Darius
 
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