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Old 01-10-2017, 02:54 PM   #1
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Calculating compression?

When using the 05 84cc heads milled .030" what is the chamber volume? Trying to determine the dish the piston needs for 9:1 cr.
Any help is appreciated...

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Old 01-10-2017, 04:51 PM   #2
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Are the heads off? Might need to measure the volume with oil minus the amount being milled off for an accurate number.
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Old 01-10-2017, 04:53 PM   #3
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Quote:
Originally Posted by FrostKing View Post
Are the heads off? Might need to measure the volume with oil minus the amount being milled off for an accurate number.
No, the heads are on the block....
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Old 01-16-2017, 07:45 AM   #4
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That's a good ? If I new that I would know my compression ratio to the T
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Old 01-16-2017, 11:03 AM   #5
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Not sure if this will help you but they have some great calculation calculators over on Wallace's site.


Milling Calculator
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Old 01-17-2017, 03:08 AM   #6
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You have to have the correct stock engine specs first.
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Old 01-17-2017, 04:29 AM   #7
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there are few hemi gurus on Moparts maybe one of those guys can help you... with out actually measuring the heads after looking at the 04 heads I have here, it looks like a .03 mill would put you right in to the quench area.
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Old 01-17-2017, 05:33 AM   #8
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Unmodified 03 heads should be 84.5 cc. These are advertised as 9.5:1cr. Using .030 stock head gasket. I've been told .035 equals .5 compression point. So milled .030 using a .030 gasket should be 9:1cr with a stock 2cc dome piston. Using a -2cc piston with a .030 gasket should be 8:5cr. Or a flat top piston using a .030 gasket is 9:1cr. That's the rough combinations I have come up with using 2cc or .035 as .5cr... will have to be measured for an exact cr.
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Old 01-20-2017, 09:26 PM   #9
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Just so I can see this in my head. So milling out a head and smoothing out the quench areas lowers your compression ratio because you have a greater volume of air left over at the end of the compression stroke therefore lowering the ratio of initial volume and ending volume? Am I understanding that right?
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Old 01-20-2017, 11:10 PM   #10
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Quote:
Originally Posted by JustHemi View Post
Just so I can see this in my head. So milling out a head and smoothing out the quench areas lowers your compression ratio because you have a greater volume of air left over at the end of the compression stroke therefore lowering the ratio of initial volume and ending volume? Am I understanding that right?
Milling a head is same as some folks call decking or planning. It only removes material from the flat mounting surface. But milling a head reduces chamber size which does rise the compression.
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