Due to the clatter in the bottom end of my 300, I expect to rebuild it soon. It's still got perfect compression, and the head was replaced with a rebuilt one about 10k miles ago, so basic rings, gaskets, and crank kit should have me ready for the next 200K or better(I'll take more care this time around). Anyway, being an injected '94, I want to play with it a little, but wonder how much I can do without going to a carb. I always drove GM products, and the computers seemed pretty 'forgiving' of performance mods, but everyone on the list seems to say that the computer on these trucks won't allow much modification to the engine. Ultimately, I want a mild cam (Comp Cams 260?), head porting, true duals w/o converters, or a free-flowing single, as well as a cold air box ala ProjectMPG. Any input on how the ECM will take this?

 

with the sort of mods you say you want to do, you shouldnt have to change anyhting on the stock computer immediatly, however someday you may want to spend a couple hundred on a custom ship to take advantage of any camming or compression changes. and IMO, that is a VERY mild cam, i would personally go with something in the 270 range, it will give a much more noticable increase in power, yet still be EFI friendly

i think the main reason why most people tend to say the the Speed density systems suck for mods is the SD mustangs, they werent well known for liking too many mods, but ive seen several trucks on this board with fairly wild things and the EFI system is still relativly intact. but again, with what youre planning, it should run just fine, but may need a chip to reach FULL potential.

 

My truck only has headers and larger injectors and the computer doesn't like it. It was actually worse with the stock injectors as far as driveability, but mileage dropped with the larger injectors. It seems to vary widely from truck to truck. I'm working on some inexpensive EFI stuff right now. Hopefully I'll get my truck dyno'd soon for baseline numbers. Then I'll finish the experiments and dyno again. I'm expecting about 25-30 hp from these things, but the only way to know for sure is to try it. I'm shooting for the end of summer for a time frame.

 

Any recommendations on a cam for the FI 300? Also, is the speed density or mass airflow better, which system does my '94 have and when did they change?

 

the mass-air is "better" in that its newer, and a lot of the newer systems respond to mods quite well. that system came out in 96, so therefore you have the SD, which can be worked around as was mentioned before.

the cam im looking at is the Crane Truck power. its a relativly newer grind, and its nice and mild yet still gives a good boost in performance. look for anything in the 260-270 duration range, and you should be fine.

silver, how bad does the truck run? i was planning on going with the hedmans ant the cam this summer, but if its going to run so bad that i cant stand it for 100 mile trips every couple weekends (must travel home from school every once in a while), im not going to chance it till i can also afford a custom chip. and can you give any hints as to your "experiments"?

 

I guess I should clarify that statement a little. The truck doesn't run bad, but I'm not getting anywhere near it's potential. The main issue is a rich condition on the low end and a lean condition on the top end. I'm looking for some software to reprogram the computer with that should fix it. With the stock injectors in place it runs very well other than an annoying part throttle miss while at constant speed. With the larger injectors the mileage in town is reduced to about 13 mpg. I drive my truck back and forth to Ft. Worth (300 miles one way) and back home to visit the folks (85 on way) fairly frequently and it isn't an issue. Also, with the stock injectors installed the truck runs absolutely horribly for 100-150 miles if the battery is disconnected. When it gets right down to it, the truck runs pretty good. It just doesn't have the perfect idle and smooth transition from idle to part throttle that it had when stock. In order to compensate I find myself driving around at WOT most of the time.

The projects I'm working on involve upper intake mods and some valvetrain mods. I prefer not to give details at this time because I don't want anyone who doesn't know what they're doing to read about it and try without it being proven. For some reason people always want to blame someone else when they screw up something they shouldn't have messed with in the first place. The intake mod should be free to someone with basic hand tools and take less than a weekend to do. I can swap the upper in about 1/2 an hour, so I might swap them and see if there is a SOTP difference to mention. You guys will be the first to know the results.

 

sounds good, my stock injectors are staying in place for now (500 bucks a summer budget for truck mods/repairs, this year is taken up already with brakes, cam, header, and exhaust). how exactly are you going to be reprogramming? i know theyres converters from the ecm port to a serial port, but theyre expensive (at least the ones ive seen), and you still gotta have the software.

 

I'm looking at several options, including the Crane Interceptor 2 that's meant for the 5.0 Stangs and an EEC Tuner meant for the 93-95 Lightning. These are both fairly inexpensive, but I don't know if they'll work. I'm working with the guy that makes the EEC Tuner to see if the 4.9 ECM is compatible with his tuner. If it is, I know where my next $300 is going.