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Discussion Starter #1
If I put the heads and intake manifold, tb, and all of that on my block....Would it not be basically the same thing as a complete 99+ GT motor?

My block is perfectly fine, low miles and all of that.

I was just wondering b/c it's a lot cheaper to swap heads and intake than it is to swap the whole motor.

Thanks
 

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About2beBAD said:
If I put the heads and intake manifold, tb, and all of that on my block....Would it not be basically the same thing as a complete 99+ GT motor?

My block is perfectly fine, low miles and all of that.

I was just wondering b/c it's a lot cheaper to swap heads and intake than it is to swap the whole motor.

Thanks
You didnt mention what year of MN-12 you have....either way, for this example, i'm going to use a '96 4.6L (like mine).

adding PI heads/intake to a '96 4.6L would yield a higher compression ratio than that of a '99+ GT motor. So it depends on what you want to do. If you want to supercharge your car, you might want to go with a '99+ motor.

If you want to go naturally aspirated, the higher compression of a PI headed '96 4.6L is perfect for 91/92 octane pump gas.

I think that's the way it goes, if I am incorrect in anyway please rest assured that one of the senior members will post the proper answers, correcting my mistakes.

check out the engine tech articles for more information on how to install PI heads if you choose to go that route.

http://www.tccoa.com/articles/engine/index.html


take care
:D
 

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Re: Re: PI Heads vs. PI Motor

66dvlbrd68 said:


adding PI heads/intake to a '96 4.6L would yield a higher compression ratio than that of a '99+ GT motor.
10.4:1

66dvlbrd68 said:

...the higher compression of a PI headed '96 4.6L is perfect for 91/92 octane pump gas.
Nothing is perfect. The compression ratio of 10.4:1 and premium gas will not cause knock. A good tune is recomended, but not required.
 

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Mod'D97LX ......... bring down the compression ratio. Larger Fuel Pump?
The only thing to lower the compression would be to change out the pistons to dished pistons. A fuel pump wont do anything for the compression
 

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BlackTbird96 said:


The only thing to lower the compression would be to change out the pistons to dished pistons. A fuel pump wont do anything for the compression
You could remove material from the heads, but that's isn't a good way.

Mod'D97LX said:
For some reason I thought the fuel pump would lower the ratio thanks
A larger fuel pump is needed to get maximum gain from PI heads.
 

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Discussion Starter #8
I have a 94 lx...

I was planning on a better fuel pump and 30# or so injectors...

I doubt I'll be supercharging this motor. Too much work to take it all down and re-enforce it.

I'd buy a forged block and build it up first, if anything....

Thanks
 

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About2beBAD said:
I have a 94 lx...

I was planning on a better fuel pump and 30# or so injectors...

I doubt I'll be supercharging this motor. Too much work to take it all down and re-enforce it.

I'd buy a forged block and build it up first, if anything....
Why are you going to use 30# injectors? Even if you go with PI heads you can use the stck 19# ones. But you can go to 24# injector if you wish. 19# injectors are good for up to 250hp. All 99-02 mustang only use 19# injectors too
 

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BlackTbird96 said:


Why are you going to use 30# injectors? Even if you go with PI heads you can use the stck 19# ones. But you can go to 24# injector if you wish. 19# injectors are good for up to 250hp. All 99-02 mustang only use 19# injectors too

Yes but they have 9:1 compression, not 10.4:1
With PI heads on a stock block, you will be needing larger injectors fairly soon.
You will need a 190lph fuel pump too.
 

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Discussion Starter #11
I just heard 30# injectors are the way to go w/ PI heads....

I thought that Stangs came w/ 24# injectors? I don't know where I got that, just heard someone talking about it, I think.
 
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