closed chamber vs open chamber

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4spdragtop said:
So the open/closed refers to the intake?? That is what Im seeing in the difference in the pics.

Thanks Rob!!
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Closed chamber refers to the combustion chamber being not the entire diameter of the bore, but just that kidney bean shaped area where the valves are. The open chamber heads have a combustion chamber that is the entire bore width in addition to the kidney bean shaped area around the valves. If you look you can see the difference. Besides the obvious compression ratio differences, the closed chamber heads allow a perfect quench on a zero deck block with .040 thickness gaskets.
 
4spdragtop said:
So the open/closed refers to the intake?? That is what Im seeing in the difference in the pics.

Thanks Rob!!
Click to expand...

Look at the area OPPOSITE the spark plug side of the chamber in the second picture. See how it is "open" compared to the same area in the first picture? That flat area of deck surface in the first pic makes quench possible. It also lessens the chamber volume and brings compression up, all other things equal. Again, first is closed, second is open. Look at the red X in each picture. It's in the same spot on each head. Now, look at the difference in that area on each head. See the difference?
 

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RustyRatRod said:
Look at the area OPPOSITE the spark plug side of the chamber in the second picture. See how it is "open" compared to the same area in the first picture? That flat area of deck surface in the first pic makes quench possible. It also lessens the chamber volume and brings compression up, all other things equal. Again, first is closed, second is open. Look at the red X in each picture. It's in the same spot on each head. Now, look at the difference in that area on each head. See the difference?
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Thanks Rob!! That explains it! Im a visual/hands-on learner, so that helps huge. So now for another question if I can??

I have heard "quench" a heckuva lot on here. What does that mean?

Im sure there will be more questions, and this seemed like the perfect thread to ask. Hope more then just me are learning something.

Oooh I hit yer "spanks" button too :prayer:
 
With the flat area of the head and the piston, when the pistons rises it essentially squishes the air fuel mixture out to the combustion area for better burn.
 
4spdragtop said:
Thanks Rob!! That explains it! Im a visual/hands-on learner, so that helps huge. So now for another question if I can??

I have heard "quench" a heckuva lot on here. What does that mean?

Im sure there will be more questions, and this seemed like the perfect thread to ask. Hope more then just me are learning something.

Oooh I hit yer "spanks" button too :prayer:
Click to expand...

Ok let's see if this helps. In the pic, look at the red X. That is the quench area. You cannot have that with an open chamber head......without a specially made quench dome piston. Essentially a piston with a dome on the "wrong" side if you will, unlike the piston in the pic. By making quench distance small (between .035 and .045") this does lots of stuff. It creates turbulence and that makes for a more complete burn and results in lower combustion temps. Which in turn allows more compression on pump gas VS the same engine without quench.
 

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Bad Sport said:
With the flat area of the head and the piston, when the pistons rises it essentially squishes the air fuel mixture out to the combustion area for better burn.
Click to expand...

RustyRatRod said:
Ok let's see if this helps. In the pic, look at the red X. That is the quench area. You cannot have that with an open chamber head......without a specially made quench dome piston. Essentially a piston with a dome on the "wrong" side if you will, unlike the piston in the pic. By making quench distance small (between .035 and .045") this does lots of stuff. It creates turbulence and that makes for a more complete burn and results in lower combustion temps. Which in turn allows more compression on pump gas VS the same engine without quench.
Click to expand...

Great knowledge and pics guys! So effectively you can define "quench" as the effectiveness of compression/combustion right??

Ya both are getting "spanked"!! LOL
 
Quench is just a tool to aid in more efficient combustion. That pretty much sums it up.
 
Oldmanmopar said:
Easier to offset grind the crank and bring the pistons out of the deck. you also get more cubes. so you increase the CR formula with more stroke. But no matter what you choose its $$$$. If it was me I would add boost. or NOS.

Cut the head and you have to cut the intake and it will never fit another set of heads. and don't forget push rod length for rocker geometry.

The cheapest and easiest would be get some pistons. or get heads.
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I had my 440 Source Stealth heads milled. 050" to raise the compression. One thing I learned is that on big block Chryslers you mill the intake surface of the heads instead of milling the intake itself. One of the engine builders here on FABO told me about it and it makes good sense. This way you don't wind up with an intake that only fits one engine. The formula is: Take the amount milled off of the combustion chamber side and multiply that number by 123% and then take that off of the intake surface on the heads. Lets say you mill the heads. .050 . .050x 123%= .0615, so take. 0615 off the intake and an un modified intake fits good. It cost me $250 to mill my heads. Thats worth it to me. A nice bump in compression and I can try a bunch of different intakes.
 
Doosterfy said:
I had my 440 Source Stealth heads milled. 050" to raise the compression. One thing I learned is that on big block Chryslers you mill the intake surface of the heads instead of milling the intake itself. One of the engine builders here on FABO told me about it and it makes good sense. This way you don't wind up with an intake that only fits one engine. The formula is: Take the amount milled off of the combustion chamber side and multiply that number by 123% and then take that off of the intake surface on the heads. Lets say you mill the heads. .050 . .050x 123%= .0615, so take. 0615 off the intake and an un modified intake fits good. It cost me $250 to mill my heads. Thats worth it to me. A nice bump in compression and I can try a bunch of different intakes.
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having them milled .050, what was your combustion chamber size afterwards?
 
tooslow said:
Did you mill the snot out of your 906's or are you still on the fence?

You guessed it Im on the fence, I have a set of 906 heads with a nice valve job and bigger valves and correct springs. My machine shop will mill them including intake for $350.
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you are almost halfway to a brand new set of aluminum heads.
 
tooslow said:
I just purchased 440 Source heads for $1064.93 to my door.Nice folks on the phone, surprised I usually do not expect customer service these days
I was going the 516 route but by the time I gave them a clean up, checked them for cracks, seats, milled them, valves?? I was to close to the 440 stealth heads in cost plus I am shaving 50lbs,
. I am going to shave them .025 to get my Compression up a full point and swap over my springs, new locks and retainers

Thanks for your help
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The 516 without a good amount of work would come up short against the 906,
You made the right decision in my opinion.
 
MOPAROFFICIAL said:
The 516 without a good amount of work would come up short against the 906,
You made the right decision in my opinion.
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What kinda "work" would you recommend to better the 516.......considering that might be the only head someone has?
 
^^Interested...

I have a set of them...

Probably involves a lot of material removal and shaping.
 
Here we go again. Here is the dyno difference on a 440 between a set of stock 906 heads and a ported set of 516 heads flowing.......

Lift............In/Ex

.100........85/62
.200......160/132
.300......210/182
.400......237.203
.500......250/216
.600......261/229

RPM...............906 TQ/HP.............516 TQ/HP

3000................431/246...............434/248
3500................441/294...............458/305
4000................438/333...............450/343
4200................444/355 ......................................peak torque w/906
4500................434/370...............470/402
4600.............................................473/414..........peak to peak TQ w/516 +29 lb-ft
4900................415/387.......................................peak horsepower w/906
5000................405/386................457/437
5300.............................................445/449..........peak to peak HP w/516 +62 HP
5400................361/372................428/440.........+67lb-ft/+68 HP
5500..................NA/NA..................421/441
5600..................NA/NA..................407/434
5700..................NA/NA..................397/431
5800..................NA/NA..................391/432
 
I think that calculates out to about plus 6.5% power increase and plus 9% torque, with an additional 400 rpm at each point.
That looks to be worth about one cam-size, or a bit more?
Since we have been talking about chamber shape;What might the compression and squish differences have been?
 
I figured you were watching IQ...funny also because I almost posted something along the lines that you'd posted something about this before.
 
AJ/FormS said:
I think that calculates out to about plus 6.5% power increase and plus 9% torque, with an additional 400 rpm at each point.
That looks to be worth about one cam-size, or a bit more?
Since we have been talking about chamber shape;What might the compression and squish differences have been?
Click to expand...

This was a really low compression engine. With the 906 heads, the pistons -.160" deck height and .039" gasket thickness we had 7.5:1 compression and approximately .299" squish.

Using the 516 heads we bumped the compression clean to 7.85:1 and shrunk the squish way down to .199".
 
I think I recall that experiment--wasn't the goal to get a hp/ci out of a stock bottom end?
 
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