PI swap and nitrous?

The 4cyl is fun, but it's also a huge pain in the ass. It's old enough and worn out enough that it needs quite a bit of work to make it safe and something you could stand to drive more than once a week (the engine is great, just everything else like the brakes, paint, suspension, exhaust, ect). I've enjoyed having the 97 as a reliable daily driver, it's up to 148k miles and still running great. I've been hesitant to do any mods on it, as I know certain mods affect NHVs and the general feeling of the car. Most mods don't have a 'factory' fit and finish to them. Even my only mod, the offroad H pipe caused a vibration in the car at low rpms where the heavier 6 cat factory pipe was very smooth.

Lately, I've been considering getting rid of the 4cyl and moving on. So tell me about the potential and pit falls of the 4.6. I read a few times that doing a PI swap on a non-PI car can give you mid-low 13s?!

What is the actual compression ratio after a PI swap on a NPI car and do you need to run premium? The 97 sometimes pings on 87 already, so I'm afraid I'll be stuck running premium if I do the PI swap. Also, will it need a tune or will the stock computer be able to keep the AFs happy? The factory tune is crap to start with, starting at 13.8:1 AF in the mid range and leaning to 12:1 by redline.

Secondly, anyone spray a PI swap 4.6? I've got a wet kit that I could easily run on the 97. I was just worrying about the compression ratio and having the extra octane to spray it. If it already requires premuim (the best we have here is 91 ) then there is no margine of safety on the nitrous. I could always make some 95-96 octane E20 by dumping in some E85 I guess.

I did some searching and found a great write up on the PI swap here: http://forums.stangnet.com/showthread.php?t=717166

I also found a company selling 'everything' needed to do the PI swap, but I am not sure how complete it really is: http://www.parkwayperformance.com/2vheadswap.asp

Looks like after the swap, better gas is needed, making 89-91 mandatory.

So what is the actual gain for this swap? I've seen numbers anywhere from 45-60+hp. Seems like the engine must really respond well to the extra compression.

I thought about an 03-04 cobra and even test drove one. That's a LOT of fun. The way power comes in is amazing. It pulls strong and steady from idle, then pulls stronger as you get to the mid range/upper rpms. Just leaves you I *shouldn't* spend that much money though.

I don't think I'd ever put boost on the '97, so I really wasn't worried about the compression ratio other than having to buy the expensive gas. A roots blower would be fun, but it would never make the horsepower it should. A centri blower just sucks (blows?), and leaves me wondering where's the boost? You don't reach full boost until nearly red line, so where's the mid range torque? You'd be better off with a turbo that doesn't spool till 4500.

Generally, I just wish the 88 wasn't such a huge piece of crap and the 97 wasn't so expensive to modify. I do want to keep the 97 for a while, as it is still a nice car and pretty rare. Still looks factory fresh when I clean it up well and runs great.

the98stang said:

Keep in mind, the high compression will leave you stranded for boost mods. With high compression, you won't really want to push more than 6-7lbs of boost through the engine. So if you plan to get a blower in the future, you are better off buying a 99+ GT. IMO, $1400 plus labor is not worth 30-35whp. I say sell the 4cyl, and buy a 03-04 cobra. Spend a few hundred in mods and your looking at 500whp

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