I just sold my quad and have a budget of around $2000. Im looking for some nice 1/4 times out of my 91 F250. It has the 7.5L, and I just put on Gibson headers, followed with a 3" Exhaust, along with a K&N Filter. I was looking into cams, but heard people complaining how they didn't work good with the EFI engine, and they threw off the computer? Also was thinking of changing to the F3TE heads with some porting done on them. Another thing I was interested in was a Tunner. I plan on spending about $1000 on a set of 33" Mud tires, so it leaves me about $1000-$1250 to have fun with.

 

The computer you have is a "speed density" computer. Generally, they don't like "fun" cams because they operate by measuring the manifold pressure (vacuum) and calculating that against temperature, the known displacement, and a variety of other things, look up a value in a data table, then squirt that much fuel into the engine.

So if you go a little overboard (overboard for the computer that is) with the cam profile, you'll throw off the vacuum in the manifold and the computer will not understand that the vacuum is cut in half because you have an awful lot of cam lift and overlap.

You can do several things... you can embark into the world of chipping and tuning, acquiring software to edit your computer's code and make adjustments that way, however the Speed Density computers aren't as well as supported as the mustang, Mass Air computers. This is actually why I'm just starting to convert my truck from Speed Density to Mass Air - Access to better and a wider variety of tools for editing the data tables. My crewcab is also speed density.

Mass air has a "MAF" which is a Mass Air Flow sensor... it measures the air going into the engine. So vacuum in the manifold isn't relevent (to the computer at least), as the computer simply measures the air going in, and uses an additional sensor which measure barometric pressure, so it knows how dense the air going in is. THEN the computer looks up a value in a table and squirts the right amount of fuel.

By using the mustang computers from 89-93, and moving some pins around in the harness and adding the two sensors (Baro and MAF) and removing the MAP sensor, you've opened the door for some serious tuning advantages. Tweecer, EEC-Tuner, GUIEEC and a few other programs do this nicely. I'm doing this not because I've changed my cam profile a lot, I haven't actually, but I'm stroking to 500cid and adding a pair of turbos. Both things a factory ford computer cannot comprehend as is.

33" mud tires for quarter mile runs? Not particularly after traction, are you

 

Sounds like MAF is the easiest way to go. How exactly would I get one, and how exactly do I set it up. Would I have to disable the speed density computer?

 

The MAF, wiring harness, and EEC go together, you need to leech it out of an 89 to 93 mustang, if you want the most popular to tune system. Then you need something like Tweecer or EEC-tuner to edit the tables to your liking, since your truck isn't a mustang and the default values in the EEC won't be close enough for you to be pleased with the outcome.

I'm doing this now on my F350 actually... time consuming but I think it will be well worth the effort to get into an EEC computer that's so pleasantly hacked and documented around the internet. Why start from scratch if you don't have to

 

Sounds like quiet a bit of work. So I'd need to go to a junk yard, and pull that out of a 89-93 mustang? On top of that would plugging that in work ok or would I need to tune it to my prefrence?

 

If memory serves the '97 460 used mass air systems; it's a one-year-only thing for the last year of the 460. Allegedly they are based on the Mustang computer & gear. Try www.460Ford.com & see if anyone can help; Byron Reynolds, a poster on that site, has a mass air conversion on his 460 (along with a ProCharger if memory serves) & has done a number of other conversions. I believe the search function there may pull up some old posts about this.

 

88-96 were speed density, 97 was speed density or mass air, depending where in that year the truck was manufactured. They crossed over somewhere in early spring, which is why the MAF-based 460's are very uncommon.

But, one can make it MAF just by using a mustang EEC, do a little rewiring, and purchasing something like Tweecer or EEC-Tuner, and using information available on the internet.

Most of the tuning software that is available is not really aimed at non-Mustang EEC's, so breaking your ***** to find a MAF-based 460 only to have the EEC not be easily hacked into, in my opinion isn't worth the effort. However, the wiring is similar, so if you dont want to move a few wires around in the EEC connector you can do it that way.

Anbd yes Oricle, it is a bit of work, but I believe the results will be well worth it. Also keep in mind the engine I'm putting into my truck is a 500cid, twin turbo stroker... so no matter what EEC or wiring I use I have to change at least some stuff, as no factory Ford truck came with this combination of "stuff".

 

I found an old mustang EFI system on ebay...maybe this could help you with your search for parts...


http://cgi.ebay.com/ebaymotors/ws/eB...category=33553

 

If I somehow found a MAF out of a 460, would that hook right up, without me having any extra wires?

 

No, you have a speed density computer. Maf sensor is mass air.

There is not shortcut. Either rewire correctly, or don't do it.

 

Ok, looks like I will be talking to some people around here and maybe get some help from our familly mechanic. Would a tuner/chip for a F250 460 still hook up fine with a mustang MAF?

 

Would swapping to the F3's through off the density computer? Since they came in the 93s+. BTW, do the chips make a nice difference, and they wont through off anything either will they? They just boost the a:f ratio right?

 

No, the trucks are speed density,a nd the mustang is mass air. If you rewire for mass air with the mustang computer, your truck is now a mustang. Shaped like a truck, but electronically its a mustang.

F3's? Please clarify. My undercaffienated brain didn't register.

Aftermarket chips vary.. most of them increase the shift points for a little more RPMs, play with the timing a little bit, and also move redline up a hair as well.

Over the years I've tried several aftermarket chips in Ford and GM vehicles, and I was never really pleased. This is why about 10 years ago, I got involved in various message forums relating to reverse engineering fuel injection, particularly eec@eelink.net (ford) and gmecm@diy-efi.org (GM) and diy-efi@diy-efi.org (all EFI hacking related).

 

When I said F3's I ment F3TE heads. They have different CC's, ect. So basiclly for a tuner/chip I have to find a chip for a 5.0 89-93 mustang? How long of a process is this conversion? Btw: the links didn't work, is there a chance you could PM me that. BTW: So with the mustang MAF, everything is changed to how a mustang would be, meaning shift points, redline, ect?

 

Well, if you're going to run EFI, you need EFI heads. The carb heads/intake and the efi heads/intake have different intake ports shape and sizes. But the exhaust ports are the same.

FTE removed the links because they were mailing lists relating to GM, Ford, and Generic DIY fuel injection.

Yes, if you put in the mustang EEC (computer) and change all the wiring and such, it will behave as if its a mustang. You can't mix and match. Well, you can to some degree, but that requires a lot more time and effort than I think you'd want to do.

If I can be honest with you... based on the questions you're asking, while they are certainly welcomed, I think this swap might be a little over your head at this point in time. I'd feel bad with you following my suggestion, and not being successful in all that is required to make it run correctly. And I'm sure you'd be equally disappointed if you didn't get it to run the way you like.