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Old 04-18-2017, 10:37 AM   #1
VB242
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How much of a compression increase on a 8v redblock head? 160 head, I believe same bowl volume as a 530.
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Old 04-18-2017, 10:59 AM   #2
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Quote:
Originally Posted by VB242 View Post
How much of a compression increase on a 8v redblock head? 160 head, I believe same bowl volume as a 530.
They told me not enough to notice.
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Old 04-18-2017, 11:07 AM   #3
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I think we're into the realm of the 'observer effect' - where the mere act of measuring it alters the result far more than what you're trying to measure.

I'm sure someone could do some maths using a rough cylindrical calculation (based on the rough diameter of the chamber), but rest assured, having a number like .007 in the calculation is going to make the result so damn close to zero as to not matter.
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Old 04-18-2017, 03:52 PM   #4
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I have a spreadsheet set up to calculate the compression ratio of my B230FT engine.
Currently it is 8.28:1.
If I took off 0.007" from the deck (i.e. the full area of the bore) it would change the compression ratio to 8.4:1.
The combustion chamber is smaller than the full area of the bore, so the answer is 'less than that', or, 'not much'.
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Old 04-18-2017, 03:59 PM   #5
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Thanks for the replies, I appreciate it's not much, but I'm pretty sure it's had .012 and then .010 taken off before as well. The dot on the cam gear doesn't line up perfectly with the notch on the valve cover anymore. I'm going to run it anyway, just curious if there was a rule of thumb per .010 taken off or anything.
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Old 04-19-2017, 09:15 PM   #6
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I measured a toothed cam pulley a while ago. It's ~4.5" or ~115mm in diameter. Circumference is then ~360mm. So, if I did the numbers right, a 1mm change in pulley height above crank centerline (either 1mm of head machining or block machining or both combined) gives 1 degree of cam rotation. In inches, .010" would be 0.25 degrees.
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