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3.9 head on 4.0 motor 

 

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 Post subject: 3.9 head on 4.0 motor
Posted: Mon Apr 24, 2006 6:15 pm 
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Does anyone know the pros and cons about fitting a head (complete) from a 3.9 litre motor onto a 4 litre block
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Posted: Mon Apr 24, 2006 6:18 pm 
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The head doesnt flow as well as the 4.0's, it will also bump the compression up compared to a 4.0 head on the same bottom end.

 

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Posted: Mon Apr 24, 2006 6:28 pm 
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Thanks for the info, I thought that there would be a reason why there would be a change, I will repair existing head(4 litre) rather than fir the good 3.9 head that I have.
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Posted: Mon Apr 24, 2006 6:31 pm 
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the 3.9 head will have smaller ports and chambers, thus increasing air velocity (up to 3000rpm) and bump up compression ratio....this will give you good bottom end torque!

wouldnt you prefer that?

 

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Posted: Mon Apr 24, 2006 6:38 pm 
Getting Side Ways
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MYLO_XR6 wrote:
the 3.9 head will have smaller ports and chambers, thus increasing air velocity (up to 3000rpm) and bump up compression ratio....this will give you good bottom end torque!

wouldnt you prefer that?


the 3.9 makes peak torque sooner, but also makes less of it.

I doubt any torque increases would be enough to notice, but you certainly will notice the loss above 3000rpm. The 3.9 will work, but if possible its better to fit the head that was designed to go on the engine.

 

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Posted: Mon Apr 24, 2006 11:59 pm 
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so the 4litres are alot better than da 3.9's are they, is it worth changin a 3.9 engine to a 4litre? is there that much difference? what are da diffrence between da two?

 

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