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Discussion Starter · #1 ·
If there are any head porting experts, can you comment on the machining of the combustion chambers in the LS7 head? I am no expert, but I have read and heard from engine builders that sharp edges and ridges in the combustion chamber are to be avoided because they will get much hotter than flat areas and could lead to detonation (pre-ignition). Maybe I should re-post this in a tech section.

If you enlarge the pic to its maximum resolution (it gets GIANT sized), you can see very sharp machining edges just above the spark plug boss.
To get the hi rez version, click the “download” link below the pic, then click the enlarge icon.
http://gm.wieck.com/forms/gm/previewpage?024297

I am guessing that this is the finished production version of the head.
 

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WOW, that is beautiful; thanks for the link! :cheers:

I'm no expert either, but one would have to assume that since they're already CNC'ing the head, it must be considered good-to-go as-is. If sharp edges were considered a problem, it would have been just as easy to program a radius versus a sharp edge.
 

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lateapex said:
If there are any head porting experts, can you comment on the machining of the combustion chambers in the LS7 head? I am no expert, but I have read and heard from engine builders that sharp edges and ridges in the combustion chamber are to be avoided because they will get much hotter than flat areas and could lead to detonation (pre-ignition).
My engine builder here in KC agrees with you totally. They build engines for the Busch Racing circuit and they have always smoothed the sharp edges in the chamber to avoid 'hot spots'!

Mike
 

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MikesZ06 said:
My engine builder here in KC agrees with you totally. They build engines for the Busch Racing circuit and they have always smoothed the sharp edges in the chamber to avoid 'hot spots'!
Sounds like an expert opinion to me! :cheers:
 

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I have another image of the LS7 combustion chamber. Mine is not as defined but very good. Also the lighting isn't the same.

The picture I am looking at doesn't appear to have the sharpness and ridges in your photo around the spark plug.

I would say the image I have has the chamber smoothed some or the lighting is hiding those ridges. I think they are smoothed.

Bottom line, I wouldn't assume your photo is finished production heads.
 

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You've been pixelized!!

The "ridges" that you think you see are reflections on a CNC ported surface that has been digitalized and enlarged. Pixel drift.

The inside of the 70 cc CNC ported LS7 combustion chamber is as smooth as a babies butt.
 

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DJWorm said:
You've been pixelized!!

The "ridges" that you think you see are reflections on a CNC ported surface that has been digitalized and enlarged. Pixel drift.

The inside of the 70 cc CNC ported LS7 combustion chamber is as smooth as a babies butt.

Nothing like heads as smooth as a baby's butt. Or something like that.
 

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Discussion Starter · #10 · (Edited)
DJWorm said:
You've been pixelized!!

The "ridges" that you think you see are reflections on a CNC ported surface that has been digitalized and enlarged. Pixel drift.
Pixelization is not a problem with this picture if you are looking at the fully enlarged version. On my 21” hi rez CRT monitor, the exhaust valve seat OD measures 12.5” across. I count over 150 pixels in just one on the small ellipse shaped “sculpts” just to the right of the spark plug boss. This is extremely good detail resolution. From examining them, I would say that my monitor is the limiting factor in resolution, not the picture itself (3,000 x 2400 pixels, or 7.2 meg picture). On a flat screen LCD monitor, one may not have sufficient resolution to be certain of what they are seeing. There are machining troughs in all 360*’s as they spiral the chamber; they all have a consistent look. There is no lighting optical illusion. The lighting is professional, these are official GM LS7 press photographs: http://gm.wieck.com/forms/gm/*query?ws4d_nav=true&[email protected]&Source=all&Page=1
Most of the other pics have similar resolution. Look at the end of the intake valve spring (on 1st page of pics); you can see every detail of the material termination fracture.

I acknowledge that with a 600% blow up, details (defects) will appear 6x larger than to the naked eye. But, I have been to CNC’s shop in Pinellas Park, Florida, and Pete’s head work (on his 5 axis machines) comes out smoother than this. I would need to have the heads side-by-side to say how much smoother.

Warhawk may be right. Maybe this is not final production.
 

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Interesting stuff, making this 1955 year old design still click, as my 1966 396 SS Chevelle has better heads, well AFR alloy heads, still a dated design compared to todays twin cam hemi-head hi-perf stuff.
As waiting for this ultimate Corvette hot-rod, and as a kid never even wanted a radio delete L-88. Now 500 hp with a CD player, hell yes, cash down for this Corvette of all time, over three months ago, and read everything about the new Z, Yep the times are a changin.
Sure nice to see all the tech stuff about this race car dry sump oiling system on this antique engine which is a must to keep the darn thing alive in any racing situation, as the ZR-1 survived quite well with out it and modified to 550 HP also no dry sump, amazing. The only down side about the overbuilt ZR-1 is a bit heavy.
So my rant is its time to let the pushrod small block to the stud farm.
A twin overcam 32 valve wet sump 500hp engine would be a neater deal than keeping the feeding tube in this current design.
And a stereo could be optional, as this music would kick Beethoven and Green Day's butt. Well maybe Green Day.
My antique is under constuction again, should be good for bout 650 hp, dunno, as a traditional hot rod money pit.
As my first Corvette was a '62 and NEW when I was 17, so have a coupla years in whats real and the dark side.
The new stuff is a lot better out of the box, beware of large hp claims as most are smoke & mirrors.
Make a few changes make for a better Z, changing the exhaust NOT, C5's Z06's are equiped with a really neat light weight exhaust, and will not change the exhaust on my new 2006 Z as its the ultimate. And the new C6 aftermarket exhaust systems are friggen Stainless steel boat anchors, they weigh a ton.
Needless to say placing a heavy item behind the rear wheels in a Hi-Perf car not a good thing, fyi.
And I sell the stuff, and as my dead friend Howard Cosell would say, "tell it like it is".
Love that factory 2006 Z stuff, 3,500r's and ooooooyheeaaa.
Nice thing bout Z owners, as not into the Bling Bling, as in a great thing.
 

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DJWorm said:
You've been pixelized!!

The "ridges" that you think you see are reflections on a CNC ported surface that has been digitalized and enlarged. Pixel drift.

The inside of the 70 cc CNC ported LS7 combustion chamber is as smooth as a babies butt.
This isn't pixel drift. It is what real CNC markings look like in the combustion chamber. I've seen enough CNC'd heads to know that the picture accurately reflects what the heads will look like. A finished CNC'd chamber is not smooth unless someone went in there an polished the chamber.

By the way, contrary to popular belief, the rough surface is in fact good for a combustion chamber. Not hard edges (i.e. around the plug hole), but a less than smooth surface is desirable. Once an atomized air/fuel mixture hits a smooth surface it will turn to liquid (droplets) again. Liquid does not burn as easily. The rough surface keeps the fuel atomized. This is one of the reasons you don't hear a good head builder talk about "polishing" the heads anymore, like you may have years ago.
 
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