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  #16 (permalink)  
Old 11-22-2012, 11:04 AM
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Originally Posted by 6426yy View Post
So I guess I should put .040" head gaskets on my 400, even though the pistons are .032" in the hole because it's not important. I guess I've got 2 more years to figure this stuff out
If you have the block machined flat corner to corner, taking off .032", you will have zero quench height.

Example:
My Speed Pro forged pistons have 1.563" compression height and measured .022" in the hole. The block deck was machined .020" for .002" quench height. The finished deck height is 9.003".

The crushed thickness of the Fel Pro head gaskets is .041" + .002" quench height = .043" Total quench height .

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  #17 (permalink)  
Old 11-22-2012, 07:30 PM
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Originally Posted by hpete View Post
I worry sometimes that we cause young people to stay on the porch because they can't afford or don't understand how to do things exactly right. Numbers matter when people are trying to legislate our hobby out of existence. On the technial side those factory motors with mega "quench" either burned leaded fuel or had extremely low compression or both. The goal is 0 quench the static clearence considers all the factors that you say we ignore.
Chevrolet small blocks used a piston deck clearance of 0.025" (piston 0.025" down the hole). This was often topped off with a steel shim head gasket that was 0.015" thick.

So 0.025" + 0.015" = 0.040" quench distance. It was when the factory went w/the round dish piston that much of the benefits of this was lost.

Many "mega quench motors" were a product of lowball rebuilders and shops who could care less about anything but their bottom line. The rest came from the backyards of America from guys who didn't know any better or were on a too-tight budget. This often meant that decks weren't milled, cheap rebuilder type 1.54" compression height round dish 4 valve relief pistons were used along w/thick composite head gaskets. Such a "build" will have upwards of 0.086" quench, with all the downsides that come with it.

I certainly do agree that rod stretch, oil clearances, thermal expansion and crankshaft/crankcase flex (which seems to have been left out of the first post, BTW) ARE all accounted for when we use 0.040" quench as a target on a wedge chamber, steel rod engine built to stay together for many thousands of miles. That figure did not happen purely by accident or on a whim of some sort. It was chosen because it is wide enough to keep the piston and head from meeting as long as the rod, crank and piston stay intact. Yet close enough to get the majority of the benefits associated w/a tight quench.

Maybe I give the youth too much credit, but I strongly believe that engine building can be grasped by any individual w/normal intelligence and enough desire. Without needing to dumb anything down, either.

Sure, at first all this talk of bearing clearances, compression/gear ratios, stall speed, air/fuel ratios, and yes QUENCH, can be confusing and even a bit intimidating. But that is no different than many things in life. If it was THAT easy, everyone would be doing it. But it's not all that easy. It takes some work. And it's because it's not that easy that it is so rewarding when you hear that engine start up the first time.
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  #18 (permalink)  
Old 11-22-2012, 08:48 PM
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Quote:
Originally Posted by mouse77 View Post
Can i ask an honest question without getting flamed (im actually fine with being flamed), or banned, or whatever?

Whats the deal with quench here?

It seems every single post that has anything remotely to do with compression ratios, theres more than a few guys on here that are fascinated with "Quench"
Most actual engine builders call it "Squish" Which is only slightly less dumb sounding than Quench.
I will use "Quench" for everyone that loves that word, but when you read it please remember i prefer Squish.

Quench is a misnomer, because the whole idea of the quench area is not to "quench" the new beginings of the combustion process, it is to give it a head start. Everyone here obviously knows what comes next, as most of you have studied the 1/8th paragraph in Smokey Yunicks 200 page book where he breezes over it. And at the end of that small paragraph it reads (Quoting offhand, but you will get the idea) Quench/squish while important, is not THAT important, as long as it is not excessive one way or the other.

How did the magical unwarrenteed HEMI that blew up all the time, so they didnt give it a warranty, even run with zero quench?
How did honda make 250 plus HP out of the S2000 with, you guessed it, little to zero quench.
*Most* Dodge 340/360/440 Engines had like .100-.125 Quench. Im not kidding. They were so poorly machined and slapped together it was common to find pistons .040 and .050 in the hole, and a dished piston, and a dished head!. Any old guys remember the quench step piston? Ya, it didnt work so great. Twas still a stone.

Heres 2 engines, that would actually benifit huge from tightening up the quench, Flathead Fords and a Briggs and Stratton.

Quench, in racing engines is used to lower detonation. It can cool the piston. It can do alot of great things.
Under sustained WOT at high operating temperatures.
In your street car. Not so much. Idle around town, take it to 6000 6500 (woooo) once a week...

Quench is almost insignifigant in street engines, it is not even worth looking at 99% of the time.
And never mind you deck the block, buy a flat top, and run a performance type gasket, i can guarentee that thing is between .050 and .040 quench. You didnt just launch a nasa missle or finally reengineer the wheel, you decked the block a got a decent piston, and somehow you engineered your quench?

Now heres the kicker: Have any of you, even once, though about rod stretch when calculating your critical, cannot deviate, must have "quench"? Theres one guy going, "Ya i have!"
You my friend, are the smartest man on this site! The rest are going "Oh man, my quench is .0xx (depending on profile and material used) tighter when my cars actually moving down the street, my dreams have been smashed!

As for real performance/racing applications, if you are doing your homework, your going to depth mike the block/piston at preassembly to get your in the hole number. THEN you calculate in rod stretch, and bearing material, and oil film compression, and then you find out your actual gotta have quench number, after of course taking into the account that different kinds of pistons do grow at different rates when they are absorbing all the combustion heat, and that they dont just grow in diameter. Then you machine the block, AFTER adding everything up.

Now i see you guys arguing over .005 in quench.....
Now we take into account that your piston grew .002 up, at 6000 your rod has streched, for arguments sake, .005, you used a digital caliper instead of a $500 depth mike, you probably didnt measure TDC and piston rock correctly with a accurate gauge and a 24 inch degree wheel, you are probably at least .010 out on your static measurements!

And you all are telling me and everyone else on here how critical quench is, and how to check it?

PLEASE, keep it realistic fellas! Anyone can use Google and look like a genius. Anyone can memorize a Yunick, or how to build a small block chevy book (which are both outdated by 20+ years now, things have changed a bit in racing engines in 20 years)

All the new guys on here, are all wound up about quench, and swirl port heads, and pushrod length, and all sorts of crap that only really matters if you race your engine. Stick to the basics. Stop being so holier than thou with each other. Try and help someone get into the hobby, instead of confusing them with wild calculations and theory. Small block chevs have made up to 365HP with all of the stuff you guys call junk. Soft exhaust seats, "too wide" "too narrow" lobe centers, small valve springs, short dual plane intakes, with exhaust manifolds!!
Then i see posts where the guys got a stone asking about something stupid like coil bind with his 480 lift 116 centerline turd cam, that might make 250 hp and you all are desktop dynoing it at 344 hp, and "you gotta use an airgap intake with a port match precisly 2 inches into the head with vortecs and 1 5/8 headers ONLY, and a .037 quench and you gotta use plasma moly rings with a 800 finish on the cyls with a burnishing brush run at 400 rpm, and a 625 edelbrock with A5 metering jets......."


We talk about pushrod length for hundreds of pages, and then most of you are running stock rockers or chinese summit rockers that are deflecting all over the place, why??
Do you have a jesel state of the art rigid valve train to warrant .117 longer custom pushrods? or will .125 do if you are using a 510 hydraulic piece of junk with lifters that compress .020 and blow all of the measurements and hours of theory out the window???

Sorry about the rant. It went longer than i expected, I couldnt take it anymore. If I dont get banned, i will try to help more, in practical ways without all the big word voodoo i see so much.
You can buy the cheapest straight edge and feeler gauges made in the crappiest factory in china, leave them out to rust for 3 years, and STILL get closer than .010" accuracy for deck clearance.
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  #19 (permalink)  
Old 11-22-2012, 09:52 PM
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Originally Posted by gearheadslife View Post
I'll never understand this ^^^ thinking..
look around, at any racing discipline. and look at the ones that are in the engine rooms.. building power that most could only dream of..
not many 60+ y/o in the room..
in fact they are the ones that tend say. it can't be done..
most said we'd never see speeds like bill eliots t-bird at superspeedways again because of the restrictor plate.. guess they where wrong..

yes guys that have been going for 30+ years have allot of good info in their gray matter..
but guys that have been learning from age 10 and are under 35 are running circles around the old pro's
so I can't see where this always comes up.. that younger means not as smart or smarter..

I think mouses post was a good one.. and pointed to things that some that ask about their build might never even think of. and most times don't have to..

cause deburing and rounding of the sharp edges of the valve releafs and spark plug threads, and anyother sharp points in the piston or champer. will do more to "quench" pre ignition than any "quench pad" measurement
Start reading posts properly and you may begin to understand them. I didn't say the older guys are better and more knowledgable because they are older. I said because they've ben DOING it much longer. Take all the "book learnin'" ya want and it won't amount to hill of beans without experience. I'll take someone with mega experience than snot nosed kid out of college...any day of the week.
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  #20 (permalink)  
Old 11-22-2012, 10:06 PM
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Originally Posted by Greg T View Post
Take all the "book learnin'" ya want and it won't amount to hill of beans without experience. I'll take someone with mega experience than snot nosed kid out of college...any day of the week.
Very well said!! I will take "real world" experience over "book smarts" any day.
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  #21 (permalink)  
Old 11-22-2012, 10:31 PM
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Originally Posted by prostreet6t9 View Post
Very well said!! I will take "real world" experience over "book smarts" any day.
I've had it up to my GRAY eyebrows with snot nosed know it all college kids trying to tell me what they learned and how my ways are wrong. I've probably built more tools through the years than they own, and i know damn well I have some really cool "tricks" to save a ton of work on any given task that only experience and ingenuity can bring.
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  #22 (permalink)  
Old 11-23-2012, 08:06 AM
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Thank you mouse. Quench is not the term i was taught many years ago it was always squish.

It drives me nuts when ppl say be sure to check your quench. Your quench should be freakin zero if you can get it there with rod stretch. For most built engines its as tight as you can get it without the pistons hitting the heads at high rpms. There is no pre set squish distance for performance engines. You have to go tight. rod stretch is .002 then squish area should be .0025 or .003 depending on the growth rate of the rods and type of abuse they will face. Sport bike engines are a great case in point. Even tho they use pentroof style heads they still have some squish area. But it is very tight.

Now if we are taling about 2 stroke dirt bike engines. Squish is very important. Has nothing to do with detonation. But very important if you want to make any power.

Chevy motors with flat top pistons are fine. If they werent they would have reshaped the pistons. It does blow me aways to see so many post about the same thing.

Then you do check it:
OK I checked it and its not up to some specs someone pulled out of there arse now what. Weld some metal onto the pistons or take the die grinder to them. No they are just fine the way they are. I bet none of these clowns has even adjusted the squish band on an engine.

As for age it does not matter. Old guy young guy whatever a four stroke engine is a set of mathmatical equations. do them right and it will run right. Experience is great if your working on a chevy motor. since they been making them for years. A new engine came out this year and you are starting from scratch with some measuring tools and a calculator.

You want to have age and experence on your team buy the right books and learn the math. The reason most engine builders are younger guy is becasue they are only highering engineers these days not ppl that say they been doing it for years. Sorry its the truth you can call Hendricks and ask for a job you will be washing parts without a engineering degree in fluid dynamics and thermal dynamics. good thing the base math has been all worked out and is easy to do. This book covers just about everything you can do to an engine. Has a nice section on squish as well. But the 2 stroke version has more info on the subject.

Amazon.com: Four-Stroke Performance Tuning: Fourth edition (9780857331250): A Graham Bell: Books Amazon.com: Four-Stroke Performance Tuning: Fourth edition (9780857331250): A Graham Bell: Books

Mouse fink: Nice Answer!
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  #23 (permalink)  
Old 11-23-2012, 09:36 AM
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Rod stretch is only a factor in the measurement when you have aluminum rods. Aftermarket forged steel, later model forged PM rods, or 1963 and later cast nodular iron rods, allowance for rod stretch is unnecessary. If someone is using aluminum rods or pre-1963 GM forged iron rods, .010" should be allowed for rod stretch. However, I doubt of anyone uses those pre-1963 "rubber" rods anymore. The pre-1963 GM forged rods were once popular just because they were "forged" but they were made of a forging that does not heat treat very well. It is difficult to find eight of those rods that do not require straightening.
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  #24 (permalink)  
Old 11-23-2012, 09:44 AM
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Originally Posted by prostreet6t9 View Post
Very well said!! I will take "real world" experience over "book smarts" any day.
I've worked with a few older guys that really have gained some insightful information through the years- and I've worked with a lot more that are WAY out of date on their information and techniques; or have found methods that require the least amount of effort from themselves to accomplish a job, not the ones that necessarily produce the best results but acceptable ones.

There's a very good reason why "fresh and new" talent is sought after by many large scientific/industrial/tech firms; depending on the industry something 5 years old can be completely obsolete.

I'm not saying the youngest around is best, but it does have a LOT of advantages over the oldest around that shouldn't be cast away.

You can also do something wrong for an entire 50 year career- it doesn't make it any more right at the end than at the beginning though. And yes there are a lot of areas where the "wrong way" will still work good enough to get results, just not optimal results.


In the end age has VERY little to do with how well a job is performed, often it comes down to ambition and intelligence.
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  #25 (permalink)  
Old 11-23-2012, 11:07 AM
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squish (skwsh)
v. squished, squish·ing, squish·es
v.tr.
To squeeze or crush together or into a flat mass; squash.

quench   /kwɛntʃ/ Show Spelled[kwench] Show IPA
verb (used with object)
1. to slake, satisfy, or allay (thirst, desires, passion, etc.).
2. to put out or extinguish (fire, flames, etc.).
3. to cool suddenly by plunging into a liquid, as in tempering steel by immersion in water.
4. to subdue or destroy; overcome; quell: to quench an uprising.
5. Electronics . to terminate (the flow of electrons in a vacuum tube) by application of a voltage.

I think squish is the more relevant word by definition.
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  #26 (permalink)  
Old 11-23-2012, 11:18 AM
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Originally Posted by malc View Post
squish (skwsh)
v. squished, squish·ing, squish·es
v.tr.
To squeeze or crush together or into a flat mass; squash.

quench   /kwɛntʃ/ Show Spelled[kwench] Show IPA
verb (used with object)
1. to slake, satisfy, or allay (thirst, desires, passion, etc.).
2. to put out or extinguish (fire, flames, etc.).
3. to cool suddenly by plunging into a liquid, as in tempering steel by immersion in water.
4. to subdue or destroy; overcome; quell: to quench an uprising.
5. Electronics . to terminate (the flow of electrons in a vacuum tube) by application of a voltage.

I think squish is the more relevant word by definition.
Thank you it is also the one the industry uses. Quench makes me think the person has not been around engines enough to pick up the lingo. Not that it means anything. Just an observation.
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  #27 (permalink)  
Old 11-23-2012, 12:19 PM
How fast is fast enough?
 
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Thank you it is also the one the industry uses. Quench makes me think the person has not been around engines enough to pick up the lingo. Not that it means anything. Just an observation.
Its like debating "motor" vs "engine" both terms are used interchangeably and neither/either is correct.
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  #28 (permalink)  
Old 11-23-2012, 12:24 PM
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Originally Posted by ap72 View Post
Its like debating "motor" vs "engine" both terms are used interchangeably and neither/either is correct.
Can´t agree, look at the definitions for quench again none qualifies for what is going on between the piston top and head at TDC.
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  #29 (permalink)  
Old 11-23-2012, 12:41 PM
How fast is fast enough?
 
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Can´t agree, look at the definitions for quench again none qualifies for what is going on between the piston top and head at TDC.
internet definitions are not only infallible but also absolute now...

Well, maybe you should write Webster then, as they left a definition out.

Also, it most certainly does "quench" pre-ignion- one of the biggest reasons so many people are obsessed with it.
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  #30 (permalink)  
Old 11-23-2012, 12:45 PM
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You mean obsolete ?
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