Please help! ‘90 k1500 tbi Chevy performance mild build crate motor

[LosDoritos]

We’ve been at this since October so I’ll try my best to put every part number here

So I have a 1990 Chevy k1500 with the tbi setup stock.
Then added these
Chevrolet Performance 350 Vortec C.I.D. 330 HP Crate Engines 19433030 Summit PN NAL-19433030
Long tube headers SPN HED-69440
Spark plugs SPN ADO-1 (wires are just part store wires)
Jegs intake manifold 555-513036 (with this we also did an EGR delete)
Trans dapt tbi adapter plate SPN TRD-2202 (we were in a hurry to get done before winter that’s why we didn’t just make one)
Holley 670cfm TBI SPN HLY-502-6
Jet Stage 2 prom chip SPN JET-29005S
Duralast Distributor AutoZonePN BDLG-GM04
Everything else is either stock or stock replacement.

Now with all that being said we’ve set the timing to a lot of things with ecm disconnected properly between 0degrees and as far up to 12 degrees (it seems to like 10 the best which is what the motor booklet says for a vacuum distributor) but no matter what it’ll hesitate, backfire out the throttle body and either stall or feel like it’s missing a good 100+ HP when it finally picks up we’ve tried different electronic distributors, even different gm ignition modules with different timing curves, and to make sure my esc module was good we took the one out of my dads truck, all of which we had laying around (money is an issue with this now so we’re trying to do everything as cheaply as possible)

Basically I’m asking if anyone else has ran into this issue with this motor/tbi combo or even may know tbi well enough to have some resolutions I also don’t really wanna do carburetor bc I live in Ohio and it’s my winter vehicle but winters can be pretty rough (plus I’m already invested deep in the tbi). we have came across a few potential solutions but it’d pretty much be me throwing $100+ at it every time I get paid, so here they are:
1. Ignition coil (I have a spare I just haven’t been able to get up to the shop to swap out)
2. Vacuum advance distributor (bear with me here) we did some research and found out you can wire up the vacuum distributor to the ignition module so the computer doesn’t throw any codes from not having the ignition module. (We don’t have an extra laying around or we’d just try it)
3. The computer is bad. (We highly doubt it’s this bc we had it on a scan tool and everything was reading great but it was something we kept seeing a lot of while researching)

We also VERY HIGHLY do not believe it is faulty wires bc when we have it at 10 degrees it WILL NOT backfire, hesitate, or act any sorts of funny IN PARK, as soon as it’s in gear it’ll hesitate and backfire, it also doesn’t want or even attempt to spin the tires. It also normally acts up more in park when it’s up to temp. I have not tried driving it cold to see if it is fine before it reaches operating temp. It’s very inconsistent

Between me (21) my grandpa who owns a shop and dad who works at said shop, we are all stumped.

If I forgot anything I’m sorry I’ll try to be keeping an eye on this and keep it updated to things I do.

 

[PlayingWithTBI]

So I have a 1990 Chevy k1500 with the tbi setup stock.
Then added these
Chevrolet Performance 350 Vortec C.I.D. 330 HP Crate Engines 19433030 Summit PN NAL-19433030

What fuel pump do you have and, what pressure are you running? The stock TBI fuel pump won't support 330 HP. For something like that, you need a fuel pump from a 96 - 97 Vortec and probably an 18LB spring. Watching your scanner, when you tip in the throttle, what does the O2 sensor do? You may be getting "lean pops".

 

[evilunclegrimace]

Yeah,,what he said^ plus you might look into getting an adjustable FPR and install a Fuel pressure gauge in the feed line right behind the TBI unit.

 

[GoToGuy]

Correct vacuum port / signal? You disconnected the ignition timing wire to set time, then reconnected after setting ignition time? Is there a conflict between vacuum dist and pcm?
Have tried to run the stock distributer just to see if it will run on stock components? And giving full control to pcm to control normal parameters, it would be worth a shot since your in tough spot now.
Good luck!

 

[LosDoritos]

What fuel pump do you have and, what pressure are you running? The stock TBI fuel pump won't support 330 HP. For something like that, you need a fuel pump from a 96 - 97 Vortec and probably an 18LB spring. Watching your scanner, when you tip in the throttle, what does the O2 sensor do? You may be getting "lean pops".

I do have a stock fuel pump. we had a fuel pressure gauge hooked up after the fuel filter and it held steady even during pops, but I do remember a few months back seeing things ab the fuel pump but we figured since it held pressure around 15-16 that it was fine, we’ll check tomorrow on the lean pops

 

[PlayingWithTBI]

we figured since it held pressure around 15-16 that it was fine

For example at 15 PSI, and 61 LB/Hr injectors, they'll support 248 HP @0.45 BSFC @ 85% Duty Cycle. At 20 PSI they will support ~286

IDK what your Chip's VE table is like but, if it's anywhere close to stock, you'll starve it at tip in all the way up to upper levels of MAP.

Your stock EP386 fuel pump will only support 230 HP where the EP381 Vortec pump supports up to 450 HP. I'm guessing, since you're maintaining fuel pressure, your VE tables are too lean.

 

[LosDoritos]

For example at 15 PSI, and 61 LB/Hr injectors, they'll support 248 HP @0.45 BSFC @ 85% Duty Cycle. At 20 PSI they will support ~286

IDK what your Chip's VE table is like but, if it's anywhere close to stock, you'll starve it at tip in all the way up to upper levels of MAP.

Your stock EP386 fuel pump will only support 230 HP where the EP381 Vortec pump supports up to 450 HP. I'm guessing, since you're maintaining fuel [ressure, your VE tables are too lean.

Would we get a map code from that at all? I’m ab to call my gpa and pick his brain with what you’ve given me so far

 

[PlayingWithTBI]

Would we get a map code from that at all?

Only if the MAP sensor isn't reading properly. It doesn't care about how much fuel is being sprayed behind it. It simply measures pressure and vacuum (the inverse of pressure). That's why I suggested looking at your O2 feedback when it starts popping.

 

[LosDoritos]

Only if the MAP sensor isn't reading properly. It doesn't care about how much fuel is being sprayed behind it. It simply measures pressure and vacuum (the inverse of pressure). That's why I suggested looking at your O2 feedback when it starts popping.

Ok so back to the fuel part, what was the 18lb spring you mentioned, and would I need a FPR for that fuel pump since that throttle body only needs 14psi I think is what the Holley book said

 

[PlayingWithTBI]

Ok so back to the fuel part, what was the 18lb spring you mentioned, and would I need a FPR for that fuel pump since that throttle body only needs 14psi I think is what the Holley book said

Don't listen to Holley, they're saying 14 PSI for a stock engine (or almost stock) I've run my stock TBI injectors as high as 28 PSI. The 18LB spring replaces the stock one in the Holley throttle body. That's what regulates your pressure. Now, I'm not sure what to say about the Holley setup, I have heard bad reviews about it.

Here's what @evilunclegrimace is talking about on a regular 220 style TB. The threaded rod with the red thumb wheel adjusts tension on the spring inside the regulator. The gauge and adapter can be found online too.

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Here's mine running with an 18 LB spring set at 20 PSI

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