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Banned
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Discussion Starter #1
Ok so I think the pistons HellHatch are selling is a great deal. BUT. Im building a Z6 block for my friend, and he wants to run forged stuff, or vitaras. He told me it is up to me, since i am building and tuning his motor. I would like to chose which ever is going to net power and be safer.

Now dont go saying run Vitaras. I would rather run forged and IF the compression ratio is less than 10.5:1 I will run them. This if for a turbo engine...

So being said. I looked up the pistons for the B7.

The Dome of the piston is -3.4CC and the Compression height is 30.8102mm in a D15B7.

But then in a Z6 is the piston Dome still -3.4CC and then is the compression height still the same, or does it lower. There is a .7mm difference in compression height on the blocks...

Do I add the .7mm difference to the Z6 setup with the custom pistons...?

I am very confused.

Or do I add the -10CC difference between volume size of the Domes?

Here are my numbers...

Z6 setup with Z6 .037 HG with Custom pistons @ -3.4cc & 30.8102mm Compression Height: Static Compression Ratio 11.31:1

Z6 setup with Z6 .037 HG with Custom pistons @ -13.4cc & 30.8102mm Compression Height: Static Compression Ratio 9.19:1

Z6 setup with Z6 .037 HG with Custom pistons @ -3.4cc & 30.1102mm Compression Height: Static Compression Ratio 10.53:1

Z6 setup with Z6 .037 HG with Custom pistons @ -13.4cc & 30.1102mm Compression Height: Static Compression Ratio 8.69

OR do I ADD the compression height difference?

Z6 setup with Z6 .037 HG with Custom pistons @ -3.4cc & 31.5102mm Compression Height: Static Compression Ratio 12.19

AND the CC difference...

Z6 setup with Z6 .037 HG with Custom pistons @ -13.4cc & 31.5102mm Compression Height: Static Compression Ratio 9.73


Please answer with the most educated answers as i would not only like to know what the CR will be but I'd like to know how you know this answer and why. I like to know the technical side of this stuff.
 

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Well?
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10,814 Posts
well if your playing with the numbers on zeal look at where it says piston to deck on the bottm, if its a number with a negative sign than the piston is actaully out of the whole if its positive thats how far below deck it .

Ok i re-read what you said compression height wont change no matter what motor its in, the piston will stay the same, just do what i said above and try ot stay at zero deck or just under
 

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Discussion Starter #3
Hm ok. So looks like its yielding

Z6 setup with Z6 .037 HG with Custom pistons @ -3.4cc & 30.8102mm Compression Height: Static Compression Ratio 11.31:1 and it is .032" out of the hole.

Now if I got std length Z6 rods machined down 1mm the piston would be .007" in the hole and have a 10.26:1 compression ratio, which is very doable...

Damn the difference in compression is damn ridiculous. So pretty much there is about a 2point increase in compression from running B2/B7 pistons in a Z6.

Compression raises from 9.24 with a Z6 HG to 11.31:1 on a 9.0:1 Compression JE/SRP...

A stock compression B7 piston is 0.028" above deck and yields 11.71:1 compression ratio...
 

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Brokedick Millionaire
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40,239 Posts
link to what is for sale isn't listed.

Z6 head may NOT accept slugs sticking up.........but a A6/B7 open chamber head will :)
 
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