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Fitting 3.9 head to 4.0ltr and vice versa! 

 

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 Post subject: Fitting 3.9 head to 4.0ltr and vice versa!
Posted: Wed Dec 06, 2006 5:56 pm 
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The xr6 i've bought is obviously a 4ltr but the head is standard, the head on my 3.9 has been port & polished.

My question is can I fit the 3.9 head to the 4ltr and are there any pro's or cons to doing so?

Also the head on the 4ltr is new and my mate who also has a 3.9ltr needs a new head, will the 4ltr head work fine on the 3.9ltr block?

Thanks

 

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Posted: Wed Dec 06, 2006 6:00 pm 
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What was done to the 3.9 head? If it has just had a port and polish I would say stick with the tickford head.

3.9 heads on 4.0 engines increase compression, 4.0 heads on 3.9 engines decrease compression.

 

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Posted: Wed Dec 06, 2006 6:04 pm 
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The 3.9 head was worked to saloon car spec and it cost me $600 can I do any damage mixing up these heads?

 

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Posted: Wed Dec 06, 2006 6:13 pm 
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RuchEa wrote:
The 3.9 head was worked to saloon car spec and it cost me $600 can I do any damage mixing up these heads?


If it was done to saloon car specs then it wasnt ported or polished as they are against the class rules. It will have the smaller 39mm exhaust valves and the swirl ridge. The 4.0 tickford head will have bigger ports, bigger valves, and a better chamber design.

 

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Posted: Wed Dec 06, 2006 10:12 pm 
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Right!!! I thought saloon series were allowed Intake Head and exhaust mods (engine wise) anyway its been port polish and shaved a few thou and it definately made a substantial difference over stock!

Again can I do any damage running the 3.9 head on the 4ltr block? And the same with runnin a 4ltr head on a 3.9ltr block?

 

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Posted: Wed Dec 06, 2006 10:32 pm 
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no, you cant do any damage.

 

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Posted: Thu Dec 07, 2006 6:03 pm 
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Sweet thanks, makes it easier to fit broadband now

 

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