5.0 engine build questions

if you are going to change all that, why would you not bore it to 4.030", put a better set of heads and intake on it and run the right cam for that package? its conceivable to easily pick up 40hp over a gt40 package by picking the right package the first time w/o spending a whole lot more money.

to start my buiild, I swapped the intake for the explorer/cobra intake from a salvage yard. I tried to go with the gt 40 heads from the salvage yard also but they didnt work out so I took them back. I also installed the F303 cam after the rebuild bored to a 308. Had a fuel pump problem so upgraded to the walbro 225 and adj regulator. at the track I found that I could peg the stock MAF so I upgraded that to the 90 mm LMAF. I tune mine with the TWEECER RT and really like it. my sig will give you some of my other mods. If you are just going to upgrade to cobra stuff you might not need to worry about tuning, MAF or injectors but, If you have bigger plans for the future you might want to look into it.

id do a 306, TFS FAC heads, holley systemax intake, billet custom HR cam from bullet racing cams, 75mm TB, accufab longtubes, 75mm TB, an AFM powerpipe, and a big MAF.

badbrains said:

Hey guys

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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.

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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.

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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?

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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?

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Yes, but I haven't read any of them. So I'll withhold comment there.

If you're looking for suggestions on top-end components, here are mine:

TFS kits have always been a top of the line decision for 302s. You'll put down near 300rwhp and you'll have a very drivable combo

My personal favorite combination for a stock 302 is AFR165 heads with an Edelbrock RPM intake, and and a custom cam from a guy like Ed Curtis. I made 320rwhp with this combo and went into the high 11s on DRs... This is a stout little combo with impressive torque. I believe I made 330 ft-lbs.

The GT40/E-cam combo you can probably piece together for cheaper, but you'll also be shooting for 260 or so RWHP. It'll make solid torque, though. That should be a solid mid-high 12-second street car depending on how heavy the car is, the gears you're running, the traction and the driver.

Good luck with your build sir

haha, no worries. Everyone starts somewhere.

If you went with the combo I recommended, you'll need to upgrade your injectors, and the stock fuel pump. Because you're going to make on the order of 300rwhp, you'll need 30lb/hr injectors, but you could get away with 24lbs/hr injectors, too. I'd recommend a GSS340-series Walbro fuel-pump. They're 255 Liters/hr, and can push enough fuel to make more than 420rwhp (the most I've pushed with one).

Some guys might tell you that you can get away with 19lbs/hr injectors, and technically they're right. However, to do that, you're going to have to drastically increase the fuel pressure which puts additional load on your fuel pump, and reduces its volumetric flow, and you're probably still going to be running over 80% IDC (injector duty cycle).

Injector duty cycle is the amount of time that an electric current is applied to the injector in order to open the injector. If you run over 80% IDC, the electrical current overheats the injector, and potentially leads to the injector going static, which means that it will start to malfunction. This can lead to the injector staying open and never closing.

Obviously you do not want to reach the maximum capacity of your injectors or you will begin to go lean.

I'd also recommend an adjustible fuel pressure regulator, which goes on the fuel rail near the passenger side fire wall. If you calibrate your MAF with your injector sizes, and install one of these, you can do a rudimentary tune on the car by increasing/decreasing the fuel pressure and pulling the spout to adjust base timing.

Chris

Chris