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Discussion Starter · #1 ·
My question is I have a 6g72 block and I was wondering if the 6g75 head will bolt up with no problems? Or can the heads from the 3.8 engine from the 4g eclipse bolt up to the 6g72 block?
 

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2001 Spyder GT
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If any one knows the answer to your question it would be @Murkrow ...Maybe this will bring it to his attention..
 

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I've been told the cylinder head volume is different but I can't cite the exact size difference. Yes they will bolt up but you may have very low or very high compression. Also the lower intake of the 75 is designed for cylinder heads that are further apart and will not fit the 72. The 72 lower intake will fit but the port size is different. If I had a spare 72 sitting around I'd throw together this exact combo and check compression for you.
 

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Discussion Starter · #4 ·
Since the heads will bolt up what is the different between the 6g72 and the 6g75 block?
I've been told the cylinder head volume is different but I can't cite the exact size difference. Yes they will bolt up but you may have very low or very high compression. Also the lower intake of the 75 is designed for cylinder heads that are further apart and will not fit the 72. The 72 lower intake will fit but the port size is different. If I had a spare 72 sitting around I'd throw together this exact combo and check compression for you.
 

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The main difference is the 75 block is taller with a longer stroke and larger bore. The taller block puts the heads further apart so there's small differences that make it work like a different lower intake, different fuel rails, different exhaust, different thermostat housing, different engine mount, different accessory brackets, different timing belt and serp belts, etc. The 75 heads have larger valves and ports as well.
 
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