Hey, we all know that the old speed / density EFI is worthless for tuning and only a fool or a poor man would waste his time trying to avoid a carburetor or MAF conversion. So now that you know a little bit about me, let's talk about tuning the old truck for more power.
My 1990 5.8L w/E4OD always ran fine, but never had the power of the carbureted 360CID SB Chevy it replaced. The old carburetor on the Chevy wasted lots of fuel, but by d**n there was plenty available when it was needed. When the F-150 tried to pull a travel trailer into a 40mph headwind, it would only go about 68mph without dropping down into second, (read: from Denver to Dallas towing a huge box at an effective wind speed of 100mph with foot to floor) and the exhaust manifolds got so hot they glowed and turned black and crackle-surfaced. The mixture was too lean, the stock EFI had probably reached its fuel delivery limit (did not have scan tool data at that time). So for 21 years I accepted the status quo. Now, the engine has been bored .040 over, for a slight increase in displacement to 355.38cid. Also a new cam with .303 lift but shorter duration than stock and 8.6:1 compression. So all these modifications seem to point toward needing to richen up the mixture. I have been driving around with my SnapOn 2500 scanner in the seat, watching temp, spark advance and fuel trim. The HEGO voltage switches and looks good, but the STFT is always reading from 0 to about 18%. It never ever reads negative. My stupid question is: If the mixture was too rich, would the data stream show a negative STFT correction? And so, shouldn't I install the adjustable fuel pressure regulator I have in hand, and starting with the same pressure noted on the original unit, increase the presure by tiny increments until I see negative fuel trim almost half the time? I want to get the fuel mixture closer to right before I mess with timing. I saw the advance showing as much as 29 degrees, which added to the base timing which is still stock at 10* sounds like it could stand a few more degrees advance at top end. Need to study the scanner while somebody else drives to tell how much is enough. Any input, comments or experiences related to the topic of fuel mixture in particular, and tuning in general of a 5.8L with S/D EFI welcome here.

 

The old speed density isn't all that terrible. Buddy ran his '87 Mustang into mid 11's with the factory shortblock, E303 cam, Trick flow heads and stock computer. He worked pretty hard with fuel pressure to make it work, but it did. He had a fuel gauge on the cowl.

Time for a fuel pressure guage and see what's it's doing at WOT under heavy load.

39* total timing is pretty steep for a small block. I suppose as long as you don't lug it down, it will be okay. My '89 F150/302 is finicky and I'd love to see what kind of total it throws at it. I bumped it up to 12* initial and it will rattle on slight inclines on the highway in OD. Had to put it back to 10*.

 

Go get yourself a wideband O2 sensor(Innovate LC-1) and then you'll know if the mixture is rich or lean. If the stock heads are still present there is no way the motor is beyond supply capacity of the stock fuel pumps or injectors so it shouldn't be running lean, but if it is an adjustable FPR may be just the ticket for a little more fuel in open loop(i.e when your foot is on the floor). The stock heads are also a big part of the reason why this motor is so much weaker than the competition from this era... they're just too damn small for 350+ cubic inches. Exactly what cam did you install in the motor BTW?

 

Agree, both the 302 and 351 were built anemic in the air flow department. They only pull up to about 3000 rpm and they are done. Kinda torquey feeling, but not big HP numbers.

 

Cam is CompCams #35-255-5. The guy at the machine shop called it a "flat tappet version of the 303 mustang cam". It does increase the exhaust lobe to .303" lift, but the lobes look pointy and the idle is very smooth. With more lift and less duration than stock, I am guessing it will add power at higher rpm. It feels just like stock at low speeds. All I can tell so far with easy break-in driving is it wants to run right past 3000rpm if I don't watch it.
Yeah, the tight ports made me not worry about buying headers. I just put some new cast iron manifolds on because they were cheap and there is nothing to be gained. As to timing, my old motor always wanted to ping on gentle upgrades, but never with heavy throttle. The live scan data stream is very interesting, because I can watch the ECM back the spark up as I tip in the gas, and advance again it on steady part throttle according to rpm. I used to run midgrade fuel to avoid retarding the base timing from spec 10*. Hope these large relief pistons will let me run regular.
I'll look into that wideband O2sensor, but mine seems to be working fine. Over .9V at times and fast switching. What I am wondering is, if the ECM sees a rich condition, will the STFT show negative fuel trim numbers? I never see anything less than 0%. Fuel pressure at WOT should be the same as with no vacuum, but the pressure with vacuum applied will rise too when I adjust the regulator. Guess I will record the pressures with OEM regulator and then go ahead and swap them to see what happens.

 

If I pushed it to downshift into D, then it ran fine. Only when it was lugging along in OD would it rattle on a slight grade. Truck has 3.55 gears and 235/75/15 tires.

With the radio or a/c on, you almost didn't hear it. Only with window down, next to barrier wall did you actually hear it making noise.

 

The short duration cam will build power in the lower RPM range.....which is OK, because you don't have the head flow to support the power in the upper ranges, and it sounds like you do some towing as well. Long tube headers will make a big improvement over the stock manifolds. The fact that the factory head/ports are so poor is all the more reason for the increased scavenging of some good long tube headers and a free flowing exhaust. A slight bump in compression would help you as well.

 

No.. it's nothing like the Ford alphabet cams, those things are all about high rpm horsepower while the one you have is the complete opposite.

No.. low rpms

On the contrary there is lots to be gained, you wouldn't believe the difference a set of longtubes make.

That's not the point, a wideband will show you the actual lambda A/F ratio of the exhaust in real time so you can not only see if the engine is lean or rich but how much.

 

All true, gentlemen. The ping was indeed almost inaudible and easy to miss, Freightrain. No trace of it now, and I am running 87octane regular. And right on about the cam performance, Conanski and blkfordsedan.
With about 125 miles on the new motor, I hitched up the trailer and took the wife to buy some garden mulch today. I hooked up the scanner. Running 75mph on the interstate with the empty trailer, I saw STFT numbers in the 2 - 8 range, with up to 18 on accel. Actually saw -1 and -2 a couple of times, so now I know the data displays negative corrections as expected. Will report on the effects of fuel pressure adjustment as I can. Cruising at 70+mph the engine turns about 2400 and is just coming into the resonant band of the intake runners. There is lots of room left under my right foot. The spark advance reads as much as 39*, and with the 10* base timing added I sure don't think it would take much more. Yet there is no trace of the old ping at steady throttle or any other time. And while on the topic of the ping, when I tore down the old motor I saw two pistons with cracked skirts that looked like they had been running cracked for some time. I have seen other motors with chunks of skirt broken out and gone missing and think this was the first stages of that process. So no more ping is good. Off the line it pulls like a beast from about 2500 to where ever. I ran it up to about 4300 one time and it was sort of losing enthusiasm you might say (still pulling hard but not any better than at 3800). So there is your low rpm cam power band for sure. The best power is from 2400 to maybe 3800 with a torque peak (according to my finely calibrated posterior) at about 2900 and that is just what I want to use. With three tractor scoops of mulch behind us on the way home, we took surface streets. I never used full throttle and could pass traffic as desired. The new torque converter is excellent, feels like new again. Mrs. says the truck is quieter than before.?!
I appreciate the commentary on breathing issues because one day soon I may build a motor for the T-Bird. That would be a high rpm application.

 

Don't want to hijack your thread but I'm running the exact same setup in my dads truck and it has no power at all. It can't even pull itself up a hill in overdrive. I have a thread going in here on it. Any ideas why it's acting that way? What plug and gap are you using. I would greatly appreciate your help. I gotta get his truck back on the road.

Will

 

Man, I saw that thread and there are lots of real good suggestions about MAF from guys who sound like they know. If you have the parts, go that way. From my personal experience (when dinosaurs roamed the earth) you could do what you want at less cost with a carburetor. Use a "torque cam" or RV grind from somebody like Melling. Typically they will have increased lift and duration over stock, with more overlap as a result. At low rpm, the long duration will cause a large part of the charge to be expelled back into the intake runner before the valve shuts. This will reduce the combustion pressure and keep it from pinging at low end, and as the rpm comes up it gets more efficient and keeps more of the mixture inside. Big valves, careful porting work and free flowing exhaust all enhance the effect. I don't know about dyno numbers, but when you press the pedal everything in the mirror should get little bitty. You can get the same power with less fuel consumption with MAF, but a carb is more forgiving. I bought Bosch platinum +2 with dual side electrodes, but I meant to buy regular Bosch platinums. Dual electrodes have fouled pretty quick for me on an old oil burning motor but should be OK on a new one. Usually use regular platinum plugs and leave them in for 50k miles or more.
Does your truck have an E4OD?

 

The truck is a 2wd e40d. Maf would be nice but I don't think that's the issue. The engine is the same as yours and it's a dog. It should have at leastas much power as yours and its not even close. The comp numbers lead me to a cracked head.

But I'm not sure.

Has your engine made good power since new or?

Thanks again
Will

 

Yes, if the STFTs are going negative then it means the ECU is pulling fuel to try and maintain stoich. It's ok for it to do that as long as it doesn't go out side the trimming window, roughly 33% in either direction. From there you just tune open loop with your adjustable FPR.

A wideband is definitely the way to go to monitor the air/fuel mixture but I would look into one that will display an A/F ratio instead of a value lambda. AEM makes a kit that, comes with a digital/analog gauge. It's as accurate as the FJO kit I run and it's right at, or less than $200.

 

OK, here is the first data with the adjustable fuel pressure regulator installed. First the numbers with the OEM reg: Warm engine idling with vacuum connected showed 36.5psi FP, 16"Hg man. vac., 520-560rpm, pulsewidth 2.61ms, STFT 1%, O2 voltage .061-.684. Fp with pump running/engine off was 43psi. Idling with vacuum disconnected saw 44psi (eyeball error?).
Installed new Accel adjustable regulator. Out of the box it gave 30psi KOEO. Set it to 43psi (same as OEM) per instructions. At idle I then saw: 36psi, 590-612rpm, 2.84ms p.w., 8%STFT, .650V O2.
So I adjusted the KOEO pressure to 45psi. Now the numbers idling with vac conected were: 37.5psi, 17 InHg vac., 552-584rpm, 2.61p.w., STFT -2 to +2, O2V .055- .655. See the STFT going both sides of zero while the vacuum increased? It is richer now. But the most interesting thing that happened was when I hauled a refrigerator for a friend. Driving 65mph up a long (est. 5%) grade at steady throttle, I saw STFT of -2 to +6. I interpret this to mean that the system is now capable of supplying more fuel than required at that load factor. I plan to increase the pressure by another pound or so and do more testing. The change from 43psi to 45psi represents about a 5% increase. I think I am almost where I want to be. Not a big noticeable power increase, but it walked up that hill with not much pedal. I hope this will stop the exhaust manifolds from glowing cherry red when I pull heavy loads. Over 200 miles on new engine now and nothing has fallen out yet!

 

Final post? Latest test had FP set to 47psi KOEO. Heavy accelertion saw STFT numbers as low as -16 (plenty of fuel now). The numbers I find significant are: climbing steep (8%+?) grade in 2nd gear at steady throttle, STFT ranged from -2 to +2. I think I will leave it set like this for a while and see what sort of fuel mileage it is getting. Probably nothing more to be gained with increased pressure. The funny part is, when I got home and turned the key to "off", the lock cylinder was disengaged...engine kept running. My ignition switch link had broken inside the tilt column. That is the goal of engineering, to have every component wear out simultaneously. I have cheated the crusher!