HP Difference 2
 

Hey guys,

Will the 99 and up heads fit the 98 4.6? I know they should fit the block but what about the intake? Or would I have to change out the heads and intake? I have the chance to get a set of heads from a 99gt but I'm not sure about the intake. Also, what would be a fair price to pay for a set of 99 heads? Intake ?

Thanks again!

The intake will not fit the '99-up heads. The ports on the 96-98 heads are oval and the ports on the PI heads are rectangular. If you swap heads you musta swap the inake manifold as well so the intake ports will match up. There are numerous kits out there to do this and they come with all the parts you'll need for the swap. There is a kit from DTA racing that comes with all the parts you need and the heads are ported and it's only $1500. You can contact Mustang works user SD WHEELER for help with this. For $1500 this kit will net you 50+ rear wheel horsepower. The PI-heads are defintiley a must for the '96-98 GT's. Once I get the extra cash the'll be on my car!

You can't just swap the heads. Since I'm not a modular guy I can't exactly remember but one of the heads has a smaller combustion chamber than the other. And I think that if you put 99+ heads on a 97-98 4.6 block you will have a high compression ratio. Try a search in this forum, I think it has been talked about in the past. Then again I could be wrong too :)

Ah.... listen to SLOW97, he probably more right than I am :o :D :cool:

Yes you are right 95MustangGT. The compression will be higher if you swap heads because the '99-up's have dished pistons (to lower compression) and the non-PI engines come with flatops. This isn't a problem unless you plan to add a blower later then you'll need to lower compression to safely run higher boost.

SLOW 97 IS CORRECT AGAIN, I PUT THE 2000 GT PI HEADS ,CAMS, AND INTAKE MANIFOLS, AND A VORTECH BLOWER.......I FORGOT ABOUT THE COMPRESSION FACTOR NOT EVEN TO MENTION THE FACT THAT I WAS RUNNING EXTREMLEY LEAN, AND I SAID GOOD BYE TO STOCK PISTON NUMBER ONE ON THE PASSENGER SIDE, THATS WHEN I INSTALLED THE JE AND MANLEY EQUIP.....IT TURNED OUT TO BE EXPENSIVE AS HELL, BUT I HAVE A VERY DURABLE ENGINE RIGHT NOW, PUSHING SOME MAJOR POWER.....:D

Yes, for all of you non-PI guys that swapped to PI heads you CANNOT (Well you probably can but it's not a good idea!) run a blower without switching to dished pistons to lower compression. Otherwise you'll fry a piston real quick due to the fact that PI heads + Non PI Flat top pistons =Between 10:1 and 11:1 compression.

So with the higher compression the 96-98 stangs with the PI heads should make more power then the 99 and up stock gts.
right?

You'll have about a 5 HP advantage over a 99-02 GT in stock form except the 96-98 will still weight nearly 100lbs more so you still may not be as fast.

Bill