|01-06-2017 11:05 PM|
A search for "engine quench" will bring up more articles/pictures...
Can build a 302" to 400+" engine into that -010 block... using aftermarket cranks...
|01-06-2017 11:37 AM|
You might wonder what all this noise of squish/quench is all about. Let me explain......
With the intake valve open and the piston descending in the bore, atmospheric pressure pushes the air/fuel mixture slug into the cylinder until the intake valve closes. Problem is, not all the fuel/air mixture is the same density. Some of it is large droplets of pure fuel that will not burn and some of it is a fog of finely mixed density that burns easily. This is where electronic fuel injection shines, it delivers a much more flammable mixture into the cylinder than a carburetor does. Neither, however, is perfect. What we need is a method of further breaking up the large droplets of liquid fuel into a flammable mixture that will burn and contribute to turning the crankshaft.
As the piston comes up to top dead center on the compression stroke, the fuel/air mixture that has been pushed into the cylinder by atmospheric pressure is trapped between the piston crown and the underside of the cylinder head. Some of it is in the combustion chamber and some of it is in an area opposite the chamber where there is a flat area on the head and a (ideally) flat area on the piston crown. The larger the area on the piston crown, the better. A perfectly flat crown with small valve reliefs might be the best design possible from a squish standpoint. If a fellow needed a piston that would allow a lower static compression ratio, requiring a dish in the piston, then a D-cup type piston crown might be the best design. As the piston approaches top dead center, the fuel/air mixture is "squished" from between the piston crown and the underside of the cylinder head with a great deal of force. It is blown over into the chamber area of the head where the turbulence tends to further break down the large droplets of fuel into a burnable mixture. This action not only helps to produce more power, it also makes the motor more "detonation-resistant" when using fuels that might be very close to detonating because of static compression ratio, fuel quality and cam timing figures.
By copious experimentation, it has been determined that the best measurement for squish is 0.035" to 0.045". You need to understand that what you put together and measure is not necessarily where everything stays when the motor is running. Even as stout as it looks, the crankpin on the crank yields a little on the upswing, bringing the piston closer to the head at top dead center. The rod will stretch a little and grow from the heat of operation (being constantly splashed with hot engine oil) and the piston will stretch a little and also grow a little due to heat of combustion. Each motor is different, of course, and uses different designs and different components, so each motor would be a little different on the minimum squish you could use before crashing the piston crown into the bottom of the head at speed. I have read of fellows who have found the part number that is on the crown of the piston, imprinted on the underneath of the cylinder head when the motor was disassembled. Now, in my opinion, that would be the optimum squish, just short of disaster.
Ford Motor Company found out about squish when they built the 1972 BB cylinder heads without a squish pad. You may want to google and read about that debacle. They had to lower the static compression ratio down into the 7's to prevent the motors from detonating.
Many people substitute the word quench for the word squish. They are, however, two completely different things. Quench is the action of bringing the piston into proximity of the cylinder head so that heat from the piston crown can be transferred to the relatively cooler metal surface of the cylinder head and then into the water jacket, to be carried away by the radiator to atmosphere. Did you ever see a blacksmith plunge a hot part into water or oil? That's quench. It is the cooling of a part. In this case, it is the cooling of a piston crown. Please do not use the word quench to describe squish. It's not the same thing.
I write the whole thing as squish/quench so that everybody knows what I'm talking about, because not everyone understands the difference.
|01-06-2017 10:07 AM|
|01-06-2017 08:17 AM|
With the steel rule and feeler gauge method, all you're measuring is the gap from the top of the piston to the block deck. In other words, how far the piston lacks coming to the very top of its bore. Normally, that would be somewhere in the neighborhood of 0.025" (twenty five thousandths of an inch) down to zero (piston crown even with the block). This photo shows that this particular build will put the piston at 0.005" piston deck height, nothing else. To reach a tight squish/quench, the builder might use a Cometic gasket that compresses to 0.036", thereby setting the squish/quench at 0.041".
If, for instance, the piston was 0.025" down in the bore, a fellow might want to use a steel shim head gasket that compresses to 0.015" when the head is bolted down. The 0.025", added to the 0.015", would make a squish/quench measurement of 0.040", right in the middle of the desired 0.035" to 0.045" squish dimension that best works to prevent detonation on pump gas.
If, for instance, the piston was 0.010" down in the bore, a fellow might want to use a composite gasket that compresses to 0.028". The 0.010", added to the 0.028", would make a squish/quench of 0.038", again, right in the middle of the 0.035"/0.045" standard that we shoot for.
If, for instance, the piston was at zero, even with the block deck, a fellow might want to use a composition gasket that compresses to 0.041", to make a squish/quench of 0.041".
If, for instance, the builder used a rebuilder piston with a shorter than standard compression height, the piston could be as much as 0.045" down in the bore, leaving no room for a head gasket if the builder was savvy about squish/quench. In this case, the block must be machined to reduce the height of the block decks and therefore bring the piston closer to the deck so that a proper gasket could be used to effect the proper squish/quench.
If, for instance, the piston popped up out of the block, perhaps because the block had previously been decked for a rebuilder piston and the current builder was using a standard compression height piston, then you might want to use a thicker composition gasket to set the squish/quench. Let's say that the piston breached the block by 0.012". You might use a gasket that compresses to 0.062". Deduct 0.012" from 0.062" and you find that you have engineered in a squish/quench of 0.040".
And again, do not confuse piston deck height with the stack height. Stack is the sum of the radius of the crank added to the connecting rod length added to the piston compression height. For instance, on a 350 Chevy, the crank radius (half the stroke) is 1.740", the connecting rod length is 5.7" and the standard piston compression height is 1.560". These 3 values add up together to make the "stack" dimension. In this case, the stack would be 9.000". The nominal block deck height from the factory is 9.025", so with a 9.000" stack fitted into the block, the piston crown would be 0.025" down in the bore and you would use a 0.015" gasket to make a 0.040" squish/quench.
This is where most amateur builders screw the pooch, they fail to know the stack and the block deck height ahead of time and end up in trouble with the piston deck height.
|01-06-2017 08:14 AM|
|01-06-2017 07:14 AM|
|01-06-2017 07:09 AM|
|01-05-2017 04:47 PM|
Here's how to find the piston deck height with a steel rule and a set of feeler gauges......
Rock the crank back and forth to find absolute top dead center before measuring. As you are standing at the side of the motor, take your reading at 9:00 O'Clock and/or 3:00 O'Clock. Taking it at Noon or 6 PM will allow the piston to rock back and forth on the wrist pin and give you an erroneous reading.
|01-05-2017 01:55 PM|
|Chevy6610||I have those things I'll check for it later, do you think there's any other engine ids anywhere other than the pad thanks.|
|01-05-2017 12:27 PM|
|01-05-2017 09:41 AM|
New 302/327/350 build
Sweet guys thanks for the feedback greatly appreciated so I didn't get the 350 I might've gotten a 3970010 302 short block previous owner said it came out of a 69 z28 it's a 4 bolt cylinders are rusty Pistons stuck, forged crank I have to pull the crank and check part numbers I can't find the engine Id cause I'm guessing it was decked at one point so I'm going off of word of mouth, well I'm trying to understand squish/quench never really heard of this term, I used a compression calculator and got 9.92:1 numbers I used bore: 4.030, stroke: 3.48, cylinder head volume: 64cc, eff Dome volume: 6.90 for those speed pros, deck clearance: 0.025 (found that on a quick Google search correct me if I'm wrong) compressed gasket thickness: 0.026, cylinders: 8, I'd like 10:1 compression ratio that's why I chose those Pistons and I'd like to turn 6k rpm, other ?s I have parts stack never heard of that sorry I'm new to all this thanks guys
|01-03-2017 05:47 PM|
Hey guys new here just got 350 block need help!!
With the 461/462 fuelie heads and using a .039 head gasket and having the block decked to zero the compression ratio will be 10.244. Use this set of pistons https://www.summitracing.com/parts/s...make/chevrolet with the fuelie heads for a 9.559 c.r.
|01-03-2017 05:38 PM|
Hey guys new here just got 350 block need help!!
Get a set of these Summit Racing pistons. They won't break the bank. https://www.summitracing.com/parts/s...make/chevrolet Rings - https://www.summitracing.com/parts/s...9-30/overview/
|01-03-2017 09:41 AM|
You will have fuel octane problems with those heads and a 350 CI + .030" engine. You may have problems with fuel octane requirements with the 327 CI engine. If the deck clearance is excessive, you will have overheating problems.
My 1962 Chevrolet Bel Air has the original 327 CI / 300 HP engine bored OS to 331 CI with 461 heads, original forged 327 crank turned .010" on rods and mains, Speed Pro forged flat top Pistons, L79 "151" cam, Pertronix Stock Look distributor, a 1967 Rochester Q-jet 800 CFM carburetor and intake manifold. The block was decked .010" flat corner to corner. It runs well on 97 octane Texaco or Exxon/Mobil with the initial advance at 10-12 degrees. It runs at 180-200 degrees on a 105 degree day with the original Harrison radiator and a good clutch fan. . I give the tank 5 gallons of VP C12 108 octane racing fuel to 15 gallons of Exxon/Mobil 97 pump gas and then advance the initial timing to 13-15 degrees, if I want to get serious. That boosts the octane to about 103 which is on the ragged edge of detonation with 15 degrees initial advance.
|01-03-2017 09:30 AM|
If you plan to run up over 5500 rpm very much, I would strongly recommend that you have ARP rod bolts put in the rods and the rod big ends resized. Resizing is a near mandatory rebuild requirement as used rods are rarely ever round on the bearing bore after 40 years of use.
You will likely find that resizing the stock rods and adding the new bolts cost-wise comes darn close to a set of brand new Sportsman level aftermarket rods like the Eagle SIR or SCAT ProStock I-beams.....and the new rods are better material and have zero cycles on them, where the stock rods likely have a cyclic count well over 1 Million cycles.
I don't even bother with stock rods anymore, just not worth the work.
The minor difference in piston weight doesn't make balancing necessary unless you are going to rev it up above 6800-7000 rpm a lot. The new rods wil come balanced closer than the stock rods, right out of the box. Everythin will still be within the factory balance tolerance.
You could also mix and match your parts....take the 4-bolt 350 block and bore it .030" over, the large journal 327 crank, the H345DCP pistons, and a set of aftermarket 5.850" rods(Eagle makes 'em in the SIR line-up) and have yourself a long rod 331" engine. Parts stack for that combo comes out to 9.023", fits right into the 9.025" stock block and allows you to use a common composition gasket at .038-.041" thick to arrive at near perfect quench clearance. Light skim cut to clean each deck of the block and your good to go.
For those guys who like the little 327 combos.
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