Someone talk me out of ditching my TBI setup

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dixiebandit69

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'90 Suburban, LO5 350.

A couple of months ago, my engine blew a head gasket, and while I had the heads off, I installed some ported small-chamber TPI heads, and an upgraded cam (204/ 214, .420"/ .443", 112 split).
Of course, the factory computer is confused by the strange MAP readings from the lower vacuum signal (15-16" hg @ 750 rpm), so I needed a chip.

I've tried FOUR of them, and none of them worked. Every time, the engine goes into "limp-in" mode and runs worse than it did before.
SES light stays on or blinks like a strobe-light; cannot retrieve any codes.
Reinstalling the factory chip eliminates this.

I've gone through the whole diagnostic procedure for this condition (from an official GM service manual), and every time it comes up being the fault of the PROM chip.
The tuner has tested the chips, and swears that they're good.

For whatever reason, this truck's ECM just doesn't like tuned chips.
At this point, I'm about ready to slap a Quadrajet and big-cap HEI on it and call it good, but that seems like a huge step backwards to me.
And I'm not getting rid of the cam.

Anyone have any arguments to keep the TBI?
 

Supercharged111

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'90 Suburban, LO5 350.

A couple of months ago, my engine blew a head gasket, and while I had the heads off, I installed some ported small-chamber TPI heads, and an upgraded cam (204/ 214, .420"/ .443", 112 split).
Of course, the factory computer is confused by the strange MAP readings from the lower vacuum signal (15-16" hg @ 750 rpm), so I needed a chip.

I've tried FOUR of them, and none of them worked. Every time, the engine goes into "limp-in" mode and runs worse than it did before.
SES light stays on or blinks like a strobe-light; cannot retrieve any codes.
Reinstalling the factory chip eliminates this.

I've gone through the whole diagnostic procedure for this condition (from an official GM service manual), and every time it comes up being the fault of the PROM chip.
The tuner has tested the chips, and swears that they're good.

For whatever reason, this truck's ECM just doesn't like tuned chips.
At this point, I'm about ready to slap a Quadrajet and big-cap HEI on it and call it good, but that seems like a huge step backwards to me.
And I'm not getting rid of the cam.

Anyone have any arguments to keep the TBI?

I'd keep it and maybe tune with this instead.

 

Supercharged111

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+1 for ditching the factory TBI and switching to an aftermarket setup like Holley. Trying to tune the factory TBI is going to be like programming a Commodore 64. It can be done but the effort is not worth it IMO.

Have you ever tuned before?
 

PlayingWithTBI

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I'd keep it and maybe tune with this instead.

EBL_Flash
I have the EBL and a WBO2 on my 88 5.7L - love it! With this combo I can tune at all ranges of the fuel tables including WOT. With this SA Excel spreadsheet (see bottom of post #3) I have a good starting point and can play with it too.
 

Kchevys

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Have you ever tuned before?
Personally, no. My 2 door had a TBI. It ran ok, a little rich, but ok. I had a few phone calls and passed a few emails back and forth with Harris Performance in Randelman, NC. Brian is/was a TBI guru and had a pretty good following on some other blogs. He took time to explain the shortcomings and challenges of the old TBI. He was the one that lead me away from the TBI.....not sure if he meant to or not. I was planning a cam swap and some other mods but I wanted to keep the TBI. In so many words, he told me that my money would be better spent on a different fuel system. I looked at some different systems and ultimately decided to LS swap.

Now if I had first hand knowledge, the equipment/software and time to devote......I may have a different outlook on TBI.
 

Supercharged111

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Personally, no. My 2 door had a TBI. It ran ok, a little rich, but ok. I had a few phone calls and passed a few emails back and forth with Harris Performance in Randelman, NC. Brian is/was a TBI guru and had a pretty good following on some other blogs. He took time to explain the shortcomings and challenges of the old TBI. He was the one that lead me away from the TBI.....not sure if he meant to or not. I was planning a cam swap and some other mods but I wanted to keep the TBI. In so many words, he told me that my money would be better spent on a different fuel system. I looked at some different systems and ultimately decided to LS swap.

Now if I had first hand knowledge, the equipment/software and time to devote......I may have a different outlook on TBI.

Sure it's less advanced than what's out there now, but even the highly revered 411 has some shortcomings that are super annoying. The TPI heads and mild cam aren't enough to justify the need for the Holley, a retuned stock computer is more than enough. If you just want the Holley, that's different.
 

PlayingWithTBI

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I had a few phone calls and passed a few emails back and forth with Harris Performance in Randelman, NC. Brian is/was a TBI guru and had a pretty good following on some other blogs.
Yeah, I started with one of his chips and was disappointed with its performance. I went to GearHead-EFI and got together with Dave w there who helped me tune my 7747 ECM. We gained quite a bit but the ECM was just too slow (160 baud) with too small VE and SA tables. That's when I went to the EBL (8192 baud). I gained somewhere around 4 seconds in 0-60 and 1/4 mile over the Harris chip plus I now have a flash ECM :biggrin:
 

chebbyfan

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I'm wanting to do an engine rebuild/swap in the future. If I ditch the TBI, what do I need to run a Holley kit on the truck?? Will I need to retain much of the sensors and wiring, or what? I was planning on a carb until reading this thread.
 
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