If i buy forged rotating assembly for my 1998 GT NPI 2v, i should have no problem if i decided to to push 600hp correct? Obviously my trans and rear wouldn't hold up to that, but engine wise i should be ok, right? And if so, which supercharger kit would you recommend? Right now i want 400-450whp, but if i want more in the future, i want a kit that can produce.

Also, im stuck between two options...

1...i can buy fully forged block

4 6 Forged Mustang Shortblock Short Block SOHC DOHC | eBay
$2500


2...Keep my block and get the parts and have them assembled somewhere

Products » Modular Engine Components » MMR » PN#400600RA MMR Street Mod 600 Rotating assembly (96-04 2 valve only)
$1500.00

Is it worth it to get the new block and have it pre assembled?

A forged bottem end should hold up to your desired goals.

If you go with option 2, keep in mind your block will need to be cleaned, honed, re-bored, etc...before buying the rotating assembly be sure to know how much overbore the block is/will be after its worked on at the machine shop. That way you know what size pistons to buy for the rotating assembly.

I personally think it's easier to buy the whole short block since it will be balanced and assembled ready for the top-end. Seems much easier and less chance of problems (assuming the engine builder does his part...).

As far as which supercharger to go with, I'll let someone else chime in...

EDI: I just looked that shortblock and it does not come with a forged crankshaft...just an FYI as that short-block is not completely forged...

Yeah i spoke with them and they said that id be better off with the 4.75 750 kit or block assembly. I guess im stuck trying to figure out if buying it fully assembled would be better straight from MMR, or buying the rotating kit, and taking it somewhere reputable. It will cost $1400 more to order the entire forged block.

Products » Shortblocks » MMR » PN#400900SE MMR 4.75 Liter Stroker Mod 900SE Shortblock

or

Products » Modular Engine Components » MMR » PN#400750SERA MMR Street Mod 750SE 4.75 Liter Forged Stroker Rotating assembly

Or for 2700 i can just get the regular 4.6 fully forged block. Considering ill be boosting it, why would i need the 4.75 anyways

Products » Shortblocks » MMR » PN#400750 MMR 4.6 Street Mod 750 (up to 750 HP) 2V, 3V or 4V (6 bolt forged crankshaft only)

As far as choice in blower - centrifugal or screw, really just depends what you want. They both have different characteristics; with a centrifugal blower, typically they do not produce any boost below 3K rpm, but when it hits they produce an increasing amount of boost that coincides with engine speed. Up to a certain point anyway. With a screw blower, they begin producing boost almost right off idle and hit their max amount of boost earlier in the rpm range and stays there.

If you compare dyno charts for engines running the two different kinds of blower, you'll see that the power curve for a centri just keeps climbing as engine speed increases toward redline, and with a screw blower it will have a much flatter curve - power increases sharply early on, say between 3000-4500 rpm, and then it just holds there.

All that said, screw blowers tend to be the more lusted after of the two due to the rush of power that's just instantly there, but many of the more powerful or fastest cars you see on a dragstrip are running a centri blower like a Vortech YSi Trim.

I think your stated goal of 450rw is reasonable and will make for a very streetable car. Lots of people daydream of bigger numbers but forget that all that power can also have a negative effect of driveability. There is such a thing as too much power. Be sure to do your homework as well on chassis/suspension and braking improvements, in the hope that your final result with the build will produce a well balanced automobile that makes killer power and can effectively put it to the ground.

I guess what I was trying to get at in my first response was that either way you go, you will be spending about the same amount of money. If you just buy the rotating assembly and get another shop to assemble it into your block, they will still need to clean, machine, re-bore, rehone you block and then install the rotating assembly so figure about $1000-$1200 for that on top of the rotating assembly ($1400)...after all that, you could have bought a new short block from MMR.

From what is sounds like, the 600HP rated short-block/rotating assembly will suit your goals just fine. I doubt you will need the 750HP rated unless you are planning a beast of a motor (and as SoCal said, it will not be as streetable...a.k.a a race setup).

Having siad all that, my advice to you is to go with the 600HP rated short block so you have a little bit of room for more HP and less hassle getting is together, plus it comes with a warranty from MMR...You can you use your current heads/intake/cams (if they are in good shape), slap a blower on it and have 450-500whp no problem.

+1 to suspension/chassis modifications....