PI Heads vs. PI Motor - TCCoA Forums
 
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post #1 of 12 (permalink) Old 08-03-2002, 11:43 AM Thread Starter
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PI Heads vs. PI Motor

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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post #2 of 12 (permalink) Old 08-04-2002, 09:47 PM
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Re: PI Heads vs. PI Motor

Quote:
Originally posted by About2beBAD
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

Mike | RSW | THP | MF | SRTConnection |

1996 Ford Thunderbird LX V8 + 1992 Ford Mustang hatchback + 1989 Ford Mustang notchback = no where else to park at my house!
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post #3 of 12 (permalink) Old 08-04-2002, 10:12 PM
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Re: Re: PI Heads vs. PI Motor

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Originally posted by 66dvlbrd68


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

Quote:
Originally posted by 66dvlbrd68

...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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post #4 of 12 (permalink) Old 08-04-2002, 10:28 PM
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What would.......

......... bring down the compression ratio. Larger Fuel Pump?

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post #5 of 12 (permalink) Old 08-04-2002, 10:43 PM
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Quote:
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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post #6 of 12 (permalink) Old 08-04-2002, 10:58 PM
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Ahh ok

For some reason I thought the fuel pump would lower the ratio thanks

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post #7 of 12 (permalink) Old 08-05-2002, 01:12 AM
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Quote:
Originally posted by BlackTbird96


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.

Quote:
Originally posted by Mod'D97LX
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.




Matt "Looks Like Egon" Davis
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post #8 of 12 (permalink) Old 08-06-2002, 04:15 AM Thread Starter
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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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post #9 of 12 (permalink) Old 08-06-2002, 06:56 AM
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Quote:
Originally posted by About2beBAD
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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post #10 of 12 (permalink) Old 08-06-2002, 11:48 AM
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Quote:
Originally posted by BlackTbird96


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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98 Audi A8 4.2Q in Racing Green Totalled
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post #11 of 12 (permalink) Old 08-06-2002, 04:26 PM Thread Starter
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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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post #12 of 12 (permalink) Old 08-06-2002, 04:57 PM
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i think cobra's use 24# but all GT's use 19# If you want to go larger go to 24#. Read the tech article on it. What size injectors It says right on there that 24# are good for 250-300hp Your not doing over 300hp so 30lb aren't needed.
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