SuperMotors.net Forums
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 Posted:10/17/2010 08:12 |
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On pre '03 Vic 4.6 were the heads different? I think that my wifes '04 Vic has different heads giving more power and on my '03 Vic motor was replaced with an older 4.6 with smaller heads? The Power is consideralbly different. thanks |
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Posted:10/17/2010 18:11 |
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The 4.6 has non-PI heads until 99, when the PI heads were developed. They offer a smaller combustion chamber than the NPI, but had a larger piston dish. Changes were made again in the 05s.
Putting the PI heads on the NPI engines WITHOUT changing the pistons will boost the compression ratio to about 10.4:1 necessitating 93 octane fuel. Some people will grind down the air dam in the chamber by the intake valve and spark plug ,and reduce the compression ratio. The flow is great, the power does increase, but not as much as higher compression.
I don't know if the 03s or 04s were part of the head changes. It is a possibility. Giving her more power.
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PROUD MEMBER of www.crownvic.net
It's just a SUPER-DUTY Mustang GT Sedan. 198K miles and still rolling HARD.
1997 Crown Victoria P71 SVT *** ex-US Marshall service (the CAR)
STOCK?? I bet it was modified. 
13.26 @ 107.24 MPH 1/4 mi w/ me, tools, & full tank of 93 octane
I added CAI, NICHE 19 X 8.5 " wheels with 245/45ZR 19 rubbers, and completely rebuilt the front end with poly bushings, Kooks headers, 2 1/4inch exhaust, TCI 2200-2400 rpm Stall converter
.PLANS:: engine upgrade, 5.4L 2v stroker, rebuild interior in leather w/ buckets, thinking about turbos
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Posted:10/18/2010 16:46 |
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04 the air box ,maf sensor and zip tube changed from a smaller size.this could be the reason i dont think the heads changed from 03 to 04. |
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Posted:3/4/2011 18:22 |
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Sorry I never got back on this one sooner. The 04 does have a larger zip tube and better flowing maf than the 03. Since we can no longer get Marauder maf and zip tubes, every one has advised to get the 04 set up instead. Talk about a kick in the pants difference that you can feel.
*******************
PROUD MEMBER of www.crownvic.net
It's just a SUPER-DUTY Mustang GT Sedan. 198K miles and still rolling HARD.
1997 Crown Victoria P71 SVT *** ex-US Marshall service (the CAR)
STOCK?? I bet it was modified.
13.26 @ 107.24 MPH 1/4 mi w/ me, tools, & full tank of 93 octane
I added CAI, NICHE 19 X 8.5 " wheels with 245/45ZR 19 rubbers, and completely rebuilt the front end with poly bushings, Kooks headers, 2 1/4inch exhaust, TCI 2200-2400 rpm Stall converter
.PLANS:: engine upgrade, 5.4L 2v stroker, rebuild interior in leather w/ buckets, thinking about turbos
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