C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette

cc in heads, after CNC

 
Old 04-16-2019, 05:22 AM
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c3_dk
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Default cc in heads, after CNC

If you have a 76cc head, and you remove 1mm by CNC, how many cc will you then gain? (or remove)
Also, does anyone know max. removal of mm before you come into problem with the block and the intake?

Thx,
John

Last edited by c3_dk; 04-16-2019 at 03:51 PM.
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Old 04-16-2019, 09:54 AM
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jackson
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Originally Posted by c3_dk View Post
If you have a 76cc head, and you remove 1mm by CNC, how many cc will you then gain? (or remove)
Also, does anyone know max. removal of mm before you cone into problem with the block and the intake?

Thx,
John
Do you mean milling 1mm (~ 0.039") from head gasket surface?

If Yes, look at this table
https://www.crankshaftcoalition.com/...cylinder_heads

According to that table, seems you'd go from 76cc to about 69cc.

In local circletrack racing, track rules for "built motors" required Iron OE production heads NO smaller than 70cc, max 1.94"-1.5" valves, max .480" valve lift, and flattop pistons.
We routinely had x487, x882 etc heads milled to just over 70cc.
We spent a lot of $ optimizing OE heads that still fit within rules ... would have been LOTS cheaper to just buy aftermarket heads, but rules are rules.
If you're building a street motor ... suggest buy aftermarket heads or iron GM Vortecs.
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Old 04-16-2019, 09:58 AM
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On your heads tech sheet it should have a statement like flat milling is 1 cc per .0065 inches. 1mm = .0394 inches

So 1mm of flat milling is about 6 cc. It should also list the max milling
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Old 04-16-2019, 10:48 AM
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Pretty easy to measure the head chambers yourself c3. 5"x5" piece of plexiglass, a graduated cylinder and some windshield washer fluid. Drill a hole near the edge of the plexiglass and seal it on the head w/vasoline. Make sure the head is level. 2 or 3 practice runs and you'll be an expert. You'll want to measure all your own volumes and won't trust published volumes any more.

Good luck.
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Old 04-16-2019, 03:01 PM
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Good info/help here THANKS all !!
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Old 04-16-2019, 06:54 PM
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Okay I found my Chevy Power Maual and it has a chart for block/head/intake milling. But 1mm is nearly 0.040" and that's off the chart in the maual. You may have to Google for a formula for this as I've seen them on line before. The biggest cylinder head cut (that would include block decking) is 0.030" and that requires 0.037" removed from the intake sides along with 0.052" off the bottom (not sure where that is). Just to note John Lingenfelter (RIP) said if heads are milled less than 0.020" it's usually not necessary to mill the intake.

Good luck.
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Old 04-16-2019, 10:25 PM
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Originally Posted by cardo0 View Post
Pretty easy to measure the head chambers yourself c3. 5"x5" piece of plexiglass, a graduated cylinder and some windshield washer fluid. Drill a hole near the edge of the plexiglass and seal it on the head w/vasoline. Make sure the head is level. 2 or 3 practice runs and you'll be an expert. You'll want to measure all your own volumes and won't trust published volumes any more.

Good luck.
Budget graduated cylinder. Accurate. 30cc syringe. Cut the point off the needle. https://www.walmart.com/ip/Mainstays...-Each/14964956

Last edited by derekderek; 04-17-2019 at 08:51 AM.
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Old 04-17-2019, 01:07 AM
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Originally Posted by cardo0 View Post
Okay I found my Chevy Power Maual and it has a chart for block/head/intake milling. But 1mm is nearly 0.040" and that's off the chart in the maual. You may have to Google for a formula for this as I've seen them on line before. The biggest cylinder head cut (that would include block decking) is 0.030" and that requires 0.037" removed from the intake sides along with 0.052" off the bottom (not sure where that is). Just to note John Lingenfelter (RIP) said if heads are milled less than 0.020" it's usually not necessary to mill the intake.

Good luck.
Thanks cardo0,
The 0.052" can that be the China walls?
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Old 04-17-2019, 08:52 AM
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Off intake where it meets the China wall.
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Old 04-17-2019, 09:48 PM
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It'll be close to 70 cc. For what you are doing (general machine work), that's close enough for the question you've asked.
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