4.6 L 3V Compression Ratio - Ford Mustang Forum
 
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post #1 of 6 (permalink) Old 07-22-2010 Thread Starter
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4.6 L 3V Compression Ratio

I'm installing upgraded cylinder heads and a new .030 overbore stroker rotating assembly in my 4.6 L 3V. I'm trying to figure out what compression ratio to shoot for with the new pistons. I'm building my engine N/A, so I want as high a compression as possible that will comfortably run 92-93 octane without knock. Does anyone have any past experience with this? I think the stock ratio is 9.8:1 and I was considering going as high as 10.0:1.

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post #2 of 6 (permalink) Old 07-22-2010
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Quote:
Originally Posted by attack46 View Post
I'm installing upgraded cylinder heads and a new .030 overbore stroker rotating assembly in my 4.6 L 3V. I'm trying to figure out what compression ratio to shoot for with the new pistons. I'm building my engine N/A, so I want as high a compression as possible that will comfortably run 92-93 octane without knock. Does anyone have any past experience with this? I think the stock ratio is 9.8:1 and I was considering going as high as 10.0:1.
Depends what kind of valve train you are going to run...


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post #3 of 6 (permalink) Old 07-23-2010
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What is the stroke and rod length. I'm running a .020 bore with a 3.750 stroke and 5.950 rod and my compression is 8.6:1

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post #4 of 6 (permalink) Old 07-23-2010
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Quote:
Originally Posted by stlwagon View Post
What is the stroke and rod length. I'm running a .020 bore with a 3.750 stroke and 5.950 rod and my compression is 8.6:1
That would be a great compression if he planned on running a blower eventually. I would stick with the compression ratio right around 10:1 for a completely N/A engine (no nitrous). He might be able to get away with 10.5:1 or even 11.5:1 if he had access to 94 octane fuel and had perfect timing with ported heads and aftermarket cams. Obviously this would take custom made rods which actually might be a little too long so it might not be possible... However, he easily could get the compression from 9.8:1 up to 10:1 just by getting a little thinner head gaskets. This is all just a guess though without doing any of the math...

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post #5 of 6 (permalink) Old 07-24-2010
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I posted this a while back. Maybe it will help you.
Attached Files
File Type: pdf compression010.pdf (482.7 KB, 930 views)

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post #6 of 6 (permalink) Old 07-24-2010
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You won’t get a significant power increase by pushing the compression ratio. I would build it at 9.25-9.5:1 so if in the future you do decide on a blower you can pop it on without having to replace the pistons.

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