Ok I have spent the last 2 days going through search results and I think I have most of what I need figured out. First of all this is going in an 89 pickup to pull my stockcar trailer. Nowhere near an f-body but this is the only good tbi forum I have found. The engine Im using is from a 91 heavy 3/4ton pu. stock block, reground 400 crank, 400 rods, flattop 350 pistons, stock vortec roller cam, 10110810 heads with some port work, stock intake and manifolds. The main RPM range is going to be in the 1500-4500 range. Not looking for a high rpm screamer, just good low end torque. getting the bottom end together is the easy part. Getting it to run is another. Ive been a professional mechanic for 13 years so I have a fairly good understanding of the tbi system.
I know I need to change the injectors to match the added displacement. From what I have been reading the 65# injectors wont be enough so I need to lookinto the 454 injectors. Of the 3 listed what is the difference? One was the high pressure version but what about the other 2?
Should I just get an adjustable fuel pressure regulator rightaway or wait and see how it runs?
Do I really need the big bore throttle body for the RPM range Im going to be using it in? Personally I think the stock one will be ok but Ive never modified a tbi setup either.
To get it to run close to perfect I will probably need a chip But for now can I get it tuned close with an adjustable regulator and mapsensor? Sorry for all the questions but I just wanted to make sure I had everything lined up before I got too far in.
Thanks
Nick

 

you are gonna need more than 2 days looking over the search.... You can follow my thread for updates: https://www.thirdgen.org/forums/tbi/...oker-plus.html

You don't necessarily have to change the injectors, if you run the 350 injectors already, I believe 55lb... what you need a "custom tune" this will change the flow rate of the injectors, to flow more fuel...

Yes, go get a regular now. Or modify the stock regulator to make it adjustable. It already is..

the 350 TB should be sufficient for a 383, that is not gonna spin higher than 5-6K

Again to get it to even run, period, you need a custom chip, to change the injector flow rate, and to change the displacement, and fuel pressure changes!

Its no band-aid fixes, thats why people go carb. But it can be done with a proper custom tune. NOT a mail order, their not to great... You can learn by yourself, or get it dynoed tune locally.

 

It really cant run any worse than it does right now. #1 has a burnt exhaust valve an 40# of compression and #4 leaks oil between the head and exhaust manifold. Need to change that plug everyother week.
As for the displacement thats the one thing that I didnt understand. The ecm doesent know the cubes. All it monitors is the rpm, throttle position and vaccuum. It goes off of a preprogrammed fuel curve thats setup for that engine. If you go bigger on cubes and change nothing the ecm will command the injectors on longer to get the proper reading from the o2 sensor. If its way above the factory setting it should set a lean code. From what I understand adding more fuel from larger injectors or higher pressure should compensate. Im not trying to argue, just understand. When you start adding aftermarket heads, bigger cam and headers then then it really changes things. basically this is going to be a stock motor with a longer stroke. Like I said not trying to argue just get a good understanding. I work in a chevy dealership but the oldest thing we get in there is 98 or so. Hardly ever get any TBI motors anymore. But I do have manuals, wiring diagrams and tools at my disposal. Thanks
Nick

 

OMG! dude, you might want to read the stickies in the TBI section....
to say the pcm doesn't calculate the displacement, is totally wrong! hell Ive even see screen shots of the software with the displacement per cylinder. So I know your incorrect on that part, that is a main function! Yes the pcm knows the cubes!

the pcm also changes the flow rate of the injectors, you can do that with the same pressure, and have the injectors flow even more... swapping out parts is wasting money to be honest! You can make your same injector flow more with a tune, if pressure is already there!

the pcm does much much more than monitor 3 sensors like you claim! boy, we all wish it was that easy. If you dont wanna fight with it, just get a carb, and adjust it to fuel and displacement..

now you have stock motor with a long stroke??? how did you make a 383 and still be stock motor? dont make sense... did you bore?

wait till the other guys read this, they are more advance than I am. and I learned everything over here and fsc!

 

I should have phrased that different. By stock motor with a long stroke I meant that the heads are stock tbi with a little porting, The cam is a stock vortec roller, stock intake and exhaust. Alot of the engines I have read about on here were vortecs or aftermarket heads, good aftermakret cam, good intake and exhaust. All of those things have an affect on tuning and combined require a major retune to function properly.
As for the sensors I know there are alot more. The temp sensor and o2 sensor also also help the ecm decide how mugh fuel to give the motor. Its alot more complicated than I made it sound.
Nick

 

so you ported some bad heads, that needs to change plugs on every other week? ok...

you must have a roller block, to use with the vortec roller cam then... I would have just got some vortec heads also... the TBI is sensitive to changes, even if its another stock cam, the pcm must be re-tuned! even if it says computer friendly...

seems to me you have made more than enuff mods, to NOT be stock! I also did not think I made alot of mods, with a 400 crank and .30 bore... but it is in fact a big difference in displacement etc...

even my stock 350, with a simple mild cam swap, k1102 ran ruff as hell on mornings etc... due to the lack of tune!

 

Huh? The motor that is in there right now is a 350. 170,000 miles running on 6 1/2 cylinders. Thats the reason for the change. I havent done anything to this one other than change plugs alot and change oil. The reason for the tbi heads is cost. I have 3 87 and newer blocks that are ready for a roller cam. I can get the cam and lifters for $50 and I have the heads. If I go with vortecs(I would like to for the record) then there is cost there, then I need an intake, and exhaust manifolds for the egr to work. Looking for the lowest cost option here, not the most HP.
Nick

 

Check out www.fullsizechevy.com theres a few trucks running 383's over there. In short it aint gonna be as easy nor as cheap as it sounds.

 

In a direct look, the ECM doesn't reference the displacement of the motor. But, the BPC which is the base pulse width for the injectors is a function of the displacement of the motor. You'll probably be ok with the stock injectors with cranked up fuel pressure. With such a tame cam and stepping up to a 383 the shift in VE may even out and stay along the same basic curve as your stock tune. If your engine is shot, you might as well toss it in and see what happens. But you'll need extra pressure out of the injectors I'm sure. It would be best if you can get into the chip and change the BPC to match and then tune the VE in.

 

Thankyou, That was kind of what I was thinking. Its gonna take some tuning I know. Like I said, It can not run any worse than it does now.
Nick