Hi, welcome to stangnet. You've come to a good place with a lot of collective knowledge on building these motors.
I am rebuilding a 1990 5.0 to go in my 90 coupe with a tremec 5 speed. I do not know a lot about the fuel injection.
It's the same thing... Just trying to cram as much air and fuel as possible into a motor before the valve shuts and then keeping the timing and AFR where they should be.
I want to build the equivelent to a cobra GT 40 engine.
These parts can sometimes be found for pretty cheap and they make a pretty streetable and torquey combo, but unless you already have the parts or are getting an absolute steal, you can do better.
Stock bottom end, Small cam, GT 40 heads,intake. what about the mass air? injectors? Do I need a new computer or how do I reflash the old?
There are a lot of mass-air meters out there. For a nice low budget n/a 302 build, I prefer the pro-flow mass air sensors like the 75mm bullet. C&L is a popular brand, and their 76mm mass air has been used with a lot of success too. Just remember that whatever route you choose to go, the mass-air MUST be matched to your fuel injector sizing. The only way to get around this is to know what you're doing with the EEC or to pay someone who does. Pro-flow (also known as Pro-M) will calibrate your MAF electronics to your fuel injector size for a modest fee. C&L calibrates a little differently by changing the sampling tube.
For injectors, my opinion (and ford's it seems) is to stay in the neighborhood of 1lb/hr for every 10rwhp. For example, stock 5.0s had 19lb/hr injectors and made 190rwhp. Cobras made around 235rwhp and had 24lb/hr injectors, '03-04 cobras made 360rwhp or so and ran 39lb/hr injectors. You can make more power from any injector by increasing the fuel pressure and keeping a close eye on the a/f ratio until you've got the bugs tuned out, but this is a good rule of thumb. With fuel injection on the stock computer, over injecting really doesn't hurt. So, if you're wondering about 2 different sized injectors that are right next to each other, go with the bigger ones. They say that the smaller the injector, the better your idle and drivability. Plenty of guys idle and drive fine with 42# injectors on 302 cubes. That's enough injector to make in excess of 500rwhp, which won't happen on a stock block unless you're using forced induction. Just make sure your MAF is calibrated right, you keep injector duty cycle below 80%, which your tuner or some quick calculations can determine, and the rest is in the tune.
For the computer, the "EEC-tuner", "TwEECer" are the most common DIY tuners. I've heard great things about the Moates Quarterhorse, too but tuning the EEC is complicated and challenging to learn as there is no difinitive book for it. If you don't want to tune it yourself, you can always take it to a dyno and let them use their piggyback of choice, such as the SCT chip. I would highly recommend a tune on any motor that does a head swap or more. If you want to tune yourself, do yourself a favor and get a nice wideband system like Innovate, AEM, Altronics, etc...
The car original had a AOD,I changed it out for a new Tremec t-5.My original motor is starting to smoke so I have another low mile engine that I am rebuilding.I have already tore it down It looks really good inside.I will start with my bore gauge on the cylinders and then check all journals to see if I need any machine work and which engine kit to buy.Any help would be appreciated.Does any one publish a book on building a high performance 5.0?
Yes, but I haven't read any of them. So I'll withhold comment there.