Missed on this combo?

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Well, thought about hauling one to the guy who flowed my Eddys. It's an hour and a half drive, another 75 bucks, and the dude ain't real helpful other than writing the numbers down.

I know damn well these are way better heads. No way no how they are not going to make more power. At least better torque. Even I can see that just by looking.

Anyone know the rule of thumb for milling closed chambers? I need to lose about 4cc's.
 
How much compression do you have now? could you live with 4 cc less compression?????
 
No way, brutha. With 68cc I'm at 11.25 to 1. I cc'd a chamber today and came up with 71.5. Rod told me they were a shade over 70.

Can't do it with head gaskets either. I run a .035 quench with the Ole Felpro 1008.

Hughes took .009 off the Eddy's, and they did measure 68 on the money. BUT, I don't know what they were before they milled them.
 
My machinist mentioned .005 per cc, off the top of his head. I hope not. Hate taking .020 off.
 
Is the combustion chamber size that important? (asking Mike and anyone else in the know)
Will a .020 cut increase horsepower by that much?
 
toolmanmike said:
Is the combustion chamber size that important? (asking Mike and anyone else in the know)
Will a .020 cut increase horsepower by that much?
Click to expand...

It's not SO much size. Or even compression ratio. It's more what happens because of it. If cutting the heads will give you better quench. And will increase the performance of the combustion chamber because of it. It will run that much better. You might only see a few horsepower. Maybe "not worth it" to some folks. But you will see a great increase in throttle response. Crispness. And general performance.

Think of some of the engines you hear. How they REALLY crackle when they idle. Really hard sharp pops from the combustion chambers. That comes partly from how "hard" the combustion is. Obviously compression ratio raises this. But so does quench and combustion chamber size. The better the "squeeze" the better the result. And it can set two nearly identical engines apart from each other.
 
His quench pad will not change as the head gets shaved(closed chambered head.
 
Cudafever said:
His quench pad will not change as the head gets shaved(closed chambered head.
Click to expand...
Exactly! wouldn't matter if my combustion chamber was 2 cc. I'd still have .035 quench. I need to stay around 11 to 1. That's the issue.
 
Ironmike said:
Well this calculator says I need to mill. 016, but it's designed for "common Pontiac heads"?

I sort of think chamber design plays a big role. Maybe I'm wrong.
Click to expand...
Chevy chart. Pontiac heads on a Chevy are a big thing nowdays
 
I'm not going to go into a big story here but that combustion chamber can cause problems if you shave too much off.
Now i have said that. Get some clay and roll it into some string and then trace your combustion chamber. Then lay it on something flat and measure how big of a circle you have. now .7854 x bore x bore x stroke so let's say you clay string circle is 3 inch so .7854 X 3 x 3 x let's say a .020" head cut. .7854 3 x 3 x .020= .141372(CI)X 16.387=2.3166 or 2.32 CC.
 
Cudafever said:
His quench pad will not change as the head gets shaved(closed chambered head.
Click to expand...

Ironmike said:
Exactly! wouldn't matter if my combustion chamber was 2 cc. I'd still have .035 quench. I need to stay around 11 to 1. That's the issue.
Click to expand...

The quench absolutely changes with milling the head. Think of it this way. As you mill the head, you close the chamber a little more. Correct? As you close that chamber. You change the "roof" of the quench area. You move it in and towards the valves. This absolutely has an effect on quench, that's why you see dish pistons with quench bands. Yes. You can set the same quench HEIGHT with the appropriate gasket. But you've still changed the quench area.

Ironmike said:
Well this calculator says I need to mill. 016, but it's designed for "common Pontiac heads"?

I sort of think chamber design plays a big role. Maybe I'm wrong.
Click to expand...

The chart just lists common pontiac stuff. The calculator still works for anything.

And yes. Chamber size plays a big role.
 
Yeah, I get it. Shape and roof of the quench isn't the way we measure it, though. I mean theoretically we measure it to the block surface of the head, which really doesn't define if it's a good or bad quench. I was strictly talking numbers.

Zero deck, with a .040 gasket and closed chamber heads. .040 quench.
 
Cudafever said:
I'm not going to go into a big story here but that combustion chamber can cause problems if you shave too much off.
Now i have said that. Get some clay and roll it into some string and then trace your combustion chamber. Then lay it on something flat and measure how big of a circle you have. now .7854 x bore x bore x stroke so let's say you clay string circle is 3 inch so .7854 X 3 x 3 x let's say a .020" head cut. .7854 3 x 3 x .020= .141372(CI)X 16.387=2.3166 or 2.32 CC.
Click to expand...
Huh? Wait a minute. With these combustion chambers there can't be a set milling amount, because the first passes will lose more cc per thou. Due to the shape, the more you mill, lesser and lesser cc'S come off per thou. Is this what ya mean?
 
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Ironmike said:
Yeah, I get it. Shape and roof of the quench isn't the way we measure it, though. I mean theoretically we measure it to the block surface of the head, which really doesn't define if it's a good or bad quench. I was strictly talking numbers.

Zero deck, with a .040 gasket and closed chamber heads. .040 quench.
Click to expand...

Why measure it that way though? Take an open chamber head. It might be .040 from the deck to head. But move .05 in, and all of a sudden it's what? When I talk about quench. I don't just mean the distance between the head and the block where the gasket sits. I'm talking the entire area between the "bottom" of the head and the deck. Not including the combustion chamber. If that makes sense, I'm probably explaining it poorly. All of that area plays a part in what we call quench.

Or think of it this way. Why do dished pistons with a quench ring exist?
 
Lustle said:
Why measure it that way though? Take an open chamber head. It might be .040 from the deck to head. But move .05 in, and all of a sudden it's what? When I talk about quench. I don't just mean the distance between the head and the block where the gasket sits. I'm talking the entire area between the "bottom" of the head and the deck. Not including the combustion chamber. If that makes sense, I'm probably explaining it poorly. All of that area plays a part in what we call quench.

Or think of it this way. Why do dished pistons with a quench ring exist?
Click to expand...
No. Your explaining exactly the way I understand it. My point was the way we measure it. In respect to a guy says he's got a .035 quench engine. I think we all figure he's got .035 from piston quench area to bottom head surface.
 
Ironmike said:
No. Your explaining exactly the way I understand it. My point was the way we measure it. In respect to a guy says he's got a .035 quench engine. I think we all figure he's got .035 from piston quench area to bottom head surface.
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Right. But what I am saying is that milling does affect the quench overall. And can give you BETTER (or worse) quench. Not necessarily tighter. The quench "chamber" can play a role just like the combustion chamber. I'm not saying milling the heads give's less or more quench. Just better or worse. Which then works with the combustion chamber to create the "squish" and give you the power you want. Improve the quench, you improve the squish, you improve power, responsiveness, detonation, everything.
 
He is right, even though the quench pad distance has not changed, the area has.
Do you understand why a quench works or what it is?
Well here is my version:)
That small space squeeze or create a fast moving chunk of air, caused turbulence in the bowl. Now i have been telling you all a long that Turbulence is BAD BAD BAD in the port, and even as it enter the combustion chamber. But when the piston is heading to TDC and there is some poorly mix fuel, Turbulence can help mix it all together better.
The fast running air from the quench, expanding into the combustion chamber allso causing a cooling effect.
Kind worried about you shaving these heads.
Haven't got the time this morning to explain why. will elaborate latter.
 
Ironmike said:
No way, brutha. With 68cc I'm at 11.25 to 1. I cc'd a chamber today and came up with 71.5. Rod told me they were a shade over 70.

Can't do it with head gaskets either. I run a .035 quench with the Ole Felpro 1008.

Hughes took .009 off the Eddy's, and they did measure 68 on the money. BUT, I don't know what they were before they milled them.
Click to expand...

I figure about .006"/cc on a small combustion chamber, so about .021" to keep it at 11.25:1. If you leave them at 71.5cc and 10.83:1 compression, and your engine makes 600HP @ 11.25:1 compression, you will be all the way down to 598HP @ 10.83:1. Mill them SOBs to 64.5cc so you can get 602HP.
 
FYI, the .005" per cc is for SBM open chamber heads. .006" or .007" per cc will be about right for these closed chamber. The 'cut-per-cc' rate won't vary all that much in the range of a .020" cut.

I'd mill them if lower RPM torque was the issue but not worry as much if peak HP is the issue. Since these are the first of these purty new shiney things, I would actually not mill them yet, run as is, and see if the outcome is satisfactory. Then mill them if the low RPM torque needed some help.
 
IQ52 said:
I figure about .006"/cc on a small combustion chamber, so about .021" to keep it at 11.25:1. If you leave them at 71.5cc and 10.83:1 compression, and your engine makes 600HP @ 11.25:1 compression, you will be all the way down to 598HP @ 10.83:1. Mill them SOBs to 64.5cc so you can get 602HP.
Click to expand...
LOL
Sarcasm at its finest.
If you all don't get the humor in this , you must be dead.
 
nm9stheham said:
FYI, the .005" per cc is for SBM open chamber heads. .006" or .007" per cc will be about right for these closed chamber. The 'cut-per-cc' rate won't vary all that much in the range of a .020" cut.

I'd mill them if lower RPM torque was the issue but not worry as much if peak HP is the issue. Since these are the first of these purty new shiney things, I would actually not mill them yet, run as is, and see if the outcome is satisfactory. Then mill them if the low RPM torque needed some help.
Click to expand...
On this type of motor...its not gonna matter.
And hey guys...you're jot gonna overload that side of the bowl with only a .020 cut.
Now bolt it on so we can see a minute increase in power already and toss more ideas at you when you aren't happy ,jk..
in the end, how much will 30 more hp have cost you though...?
 
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