Having had some injector problems, AND not being satisfied with the performance offered by the modifications I had made to my truck AND after doing a little research and talking with fellow FTE user '89F2urd about a similar swap I decided to give the 24 lb injector swap a shot.

For some background information, my 89 F-250's 351W was already sporting a set of ported GT40s with 1.7 rockers, a 351 HO cam and shorty headers and upgraded exhaust. It ran good, but not the way I thought a truck with 4.10 gears and an upgraded 351 should run. I recently chased a pair of bad fuel injectors for four months. During the chase I went ahead and upgraded the intake to a Professional Products Typhoon intake with a 70mm throttle body and a Crane Cam 444232. I also got shed of the crappy Pro-Form 1.7s and found a used set of Cobra Crane 1.7s for $75.

After bolting it all back together, I was VERY underwhelmed with the trucks performance and started researching using the 24 lb injectors. '89F2urd used a 460 ECM (because it is programmed to handle the 24 lbers as that's what they come with from the factory) along with a wideband O2 sensor and an adjustable fuel pressure regulator so he could get his Air/Fuel ratios where he wanted them, particularly in the higher RPM range.

So, I threw caution into the wind and purchased a set of injectors off Craigslist and an adjustable fuel pressure regulator for a whopping $150 and found a 1 ton with a 460 and a 5 speed in the junkyard and bought the ECM for $20 and installed everything in an afternoon, setting the fuel pressure to 34 lbs. However, I didn't run down a wideband O2 sensor... I got impatient.

The results were surprising to say the least. I didn't think the big truck could run as good as it does now. Immediately the truck ran better across the whole RPM range. The change in performance is comprable to swapping a 2 barrel carb for a 4 barrel carb and intake - the truck does EVERYTHING better.

During everyday driving the truck never seems to strain (even when pulling a grade in 5th gear) and can even peel the 285-75-16 tires from a stand still. In the towing department, the truck pulls my 16-foot gooseneck car trailer like a champ and pulls the camper like its not even there.

So far, the truck has also remained trouble code free.

I did run across a few draw backs. First off the truck ran notably rich at idle, even producing a little blue exhaust smoke when cold. To remedy this I cut the fuel pressure back to 31-32 lbs and the rich condition subsided...exhaust cleared right up. I think if I had the wideband O2 sensor I could clean the rich issue up completely. The second issue I have is with the ECM. The '88 1-ton ECM is governed at 4500 rpm vs the 5500 rpm, but since I don't run around at wide open throttle, its no big deal.

Fuel economy dropped, but only a little. Around town I still get about 13-15 mpg, and on the highway I get about the same running between 60 and 65. Above 65 mph, however, fuel economy goes in the bucket. Pulling the camper at 70 and up on Memorial Day weekend I saw as bad as 8 mpg, but when I took my foot out of it mpg comes back up to around 13.

For anyone considering swapping in the bigger injectors I would recommend that they do all the upgrades I have to improve air flow through the engine...especially the good flowing heads, intake and improved exhaust. Given the intakes and heads available for Windsor engines, it doesn't take too much to make a 351 move the amount of air that the cruddy EFI big blocks of the early 90s did.

Just remember you must run the 460 ECM to make the swap work.

 

I would be interested to see how the AFR looks through the REV range. Sounds like it works for you. I am going the way of a MAF conversion and tuner for my truck so I can fine tune it to run exactly the way it should. Yet again I am throwing around the idea of some MAJOR engine upgrades... Displacement mainly.

 

I bet it will be lean up top. So I would leave the rev limiter at 4500 if I were you.
I'd still rather convert to MAF. Did it with my car and have never looked back.

Oh and I think that the fuel pressure with the vacuum line connected should be around 30, and 39 with the vacuum line off the regulator.

 

I have no plans of changing the rev limiter...I don't hot rod the truck around like its a fox body...I just wanted performance that would reflect the modifications that I had done and make the truck perform better.

And as for the fuel pressure, I know its supposed to be 30-32ish with vaccum to the regulator and 40 without, I just started with a higher fuel pressure to make sure there was plenty of fuel for the bigger injectors and then tuned as needed.

If I had started with a wide band O2 with the 19 lbers and then stuck in the 24 lbers I could give you some relative data, comparing one set to the other I suppose, but still it would only be relative because I wouldn't know what the stock A/F ratios were before I started modifiying the truck and before the ECM would have bumped up the injectors' duty cycle to compensate for the modifications.

I'm sure the truck could benefit from a MAF swap, but honestly I don't see any need for it as the truck runs like a scalded dog and with about $175 for the whole swap its honestly cheaper than hunting down an A9L ECM and then buying the harness adapter and re-pinning connector. Maybe its the lazy and cheap way, but frankly it works too well to argue with, especially when I bought the truck for $1,000 a few years ago anyway.

 

By all means, if it works, run it. My curiosity is just in seeing if it has any issues higher in the rev range leaning out, or running rich at lower rpm's. This might be a viable option for those looking for a bump in power without MAF swapping. I plan to build some kind of stroker in the future for my truck which is why I am going the route of a MAF swap.

 

Definitely...Strokers need more cam than SD can provide...more duration and more lift. MAF is the way to go and realistically they are the most efficient engine manigement system for a modified truck...I was just being lazy and wanting an easy way to go for my old truck.

 

You can always dyno tune an SD system with whatever mods you want. Or you can get a stand alone engine management system and not have to deal with a MAF either.