383 Vortec/TBI Build Thread

[84 M1008]

I had a 97 Z71 shortbread 5.7 Vortec that was a complete nightmare. I replaced the CSFI with the MPFI spider and shortly after that, actually within a week, I drove the truck about 100 feet and the engine stalled out and locked up. It ran like a monster after the upgrade so I couldn't understand what happened. Come to find out the injectors stuck open and flooded the engine hydrolocking it. It had ongoing 02 sensor problems and false misfire codes popping up so that must have had something to do with it. I'll stick to diesels.

 

[Daveo91Burb]

Dammit - more exhaust leaks. Found two more in my new custom Y-pipe in two different welds. Will be going back to the shop for him to fix up. Can exhaust shops do pressure tests of their work? I found the first one by starting it up cold and running my finger along the welds. I had to get a little more creative to find the two tonight. Who knows maybe more will show up after these two get fixed.

All these problems are upstream of the O2 sensor and cat. I'm sure they're not making my TBI tuning efforts any easier.

 

[4WDKC]

Dammit - more exhaust leaks. Found two more in my new custom Y-pipe in two different welds. Will be going back to the shop for him to fix up. Can exhaust shops do pressure tests of their work? I found the first one by starting it up cold and running my finger along the welds. I had to get a little more creative to find the two tonight. Who knows maybe more will show up after these two get fixed.

All these problems are upstream of the O2 sensor and cat. I'm sure they're not making my TBI tuning efforts any easier.

Correct, they will cause you a headache. Next time may want to make it out of stainless steel and have someone tig weld it, they can purge the pipe and help the weld and make it seal.

 

[Daveo91Burb]

Correct, they will cause you a headache. Next time may want to make it out of stainless steel and have someone tig weld it, they can purge the pipe and help the weld and make it seal.

Yeah, I've never thought stainless was really worth the extra cost, but didn't know the part about using a TIG weld and purging.

 

[4WDKC]

Yeah, I've never thought stainless was really worth the extra cost, but didn't know the part about using a TIG weld and purging.

Its almost rust proof, holds heat better and is stronger than mild steel.

 

[Daveo91Burb]

After months of trying I think I've finally gotten all the exhaust leaks resolved. Took it back to the shop three times for him to fix various pinhole leaks in welds that I found by duct taping my shop vac to the tail pipe. They were legit leaks and he fixed them, but they weren't the source of the noise I kept hearing. Finally found a mangled #8 exhaust manifold gasket. Fixed that and all quiet now. Still have some tuning issues to resolve (mostly idle and decel) but I'm hoping now I can actually make progress on them without chasing my tail. Not sure what happened here.... my only real guess is I had it cockeyed when I originally installed the manifold???

You must be registered for see images attach

 

[4WDKC]

After months of trying I think I've finally gotten all the exhaust leaks resolved. Took it back to the shop three times for him to fix various pinhole leaks in welds that I found by duct taping my shop vac to the tail pipe. They were legit leaks and he fixed them, but they weren't the source of the noise I kept hearing. Finally found a mangled #8 exhaust manifold gasket. Fixed that and all quiet now. Still have some tuning issues to resolve (mostly idle and decel) but I'm hoping now I can actually make progress on them without chasing my tail. Not sure what happened here.... my only real guess is I had it cockeyed when I originally installed the manifold???

You must be registered for see images attach

mine had one of the studs for the exhaust manifold break, I was later told that is a common problem of the 4x4s..maybe something to keep in mind.

 

[eskimomann209]

When I did my ls swap the bolts on the driver manifold backed out
I used stainless bolts on an alum head and I tightened them three times and it still happened
Blew out my gasket too ...
Glad you found it
Exhaust leaks make even a nice looking truck sound like a hoopdie

 

[Daveo91Burb]

Been a while since I've updated status on my 383 build. Last post was about a PS exhaust manifold leak, since then I had to do the same with DS manifold! Not sure what's going on with my exhaust leaks, but I hope I have them licked finally.

But most of my effort has been on tuning. Lots of data logging and making small changes to the .BIN file based on those logs. Fueling table is looking pretty good finally, but there are other issues still to resolve. Biggest issue: a surge or oscillation during engine braking. RPM will fluctuate up to 400 rpm high to low while slowing down in gear. Complete cycle lasts about 1 second and will keep cycling until there is no negative load on engine. Doesn't seem to cause a big problem mostly just annoying and frustrating that I can't resolve it. I've ruled out the PCM and chips in it, most or all of the sensors, and host of things in the tune. Guys at Gearhead EFI have not been much help, probably because the '91-'93 PCM for a 4L80e is so uncommon - no one has much experience with them. Haven't tried thirdgen.org, but am thinking about it.

For anyone that either has a 4L80e tranny or is thinking about converting...there are some things to be aware of. Mainly, '91-'93 was a breed all its own. Significant changes were made in '94 and again in '95. Early force motor was different and required periodic cleaning that was controlled by the PCM (Powertrain Control Module, aka "the computer"). AFAIK, the only GM PCM that can do this is 16147060 that came in '91-'93 2500/3500 trucks that had 4L80e. '7060 works fine and is tunable, but does not have the support from the tuner crowd that later PCM's have, specifically the 16197427 that came in later heavy duty trucks AND many many half tons since it was also used with the 4L60e tranny. In '94 they changed the force motor to a Holley design that did not require the periodic cleaning. This one may be the sweet spot for square 4L80e conversions since I think it was the last year of the solid style shift linkage - in '95 sounds like they went to a cable linkage that requires some mods to either tranny or linkage for compatibility with our trucks. Whatever you do make sure to get a control module (OEM or aftermarket) that is fully compatible with the year tranny you're using. I have no idea if the aftermarket control modules will work with the early tranny and do the cleaning, I'm guessing not.

 

[yevgenievich]

Aftermarket controllers can deal with early trans but have to be programmed for it. I wonder if you tried loading a stock bin with just injector parameters adjusted and see if you get the same cycling. It will run worse everywhere else, but will give you an idea of what parameters are causing the issue. I can also read the bin from my stock 91 if that would be of any use.

 

[4WDKC]

Been a while since I've updated status on my 383 build. Last post was about a PS exhaust manifold leak, since then I had to do the same with DS manifold! Not sure what's going on with my exhaust leaks, but I hope I have them licked finally.

But most of my effort has been on tuning. Lots of data logging and making small changes to the .BIN file based on those logs. Fueling table is looking pretty good finally, but there are other issues still to resolve. Biggest issue: a surge or oscillation during engine braking. RPM will fluctuate up to 400 rpm high to low while slowing down in gear. Complete cycle lasts about 1 second and will keep cycling until there is no negative load on engine. Doesn't seem to cause a big problem mostly just annoying and frustrating that I can't resolve it. I've ruled out the PCM and chips in it, most or all of the sensors, and host of things in the tune. Guys at Gearhead EFI have not been much help, probably because the '91-'93 PCM for a 4L80e is so uncommon - no one has much experience with them. Haven't tried thirdgen.org, but am thinking about it.

For anyone that either has a 4L80e tranny or is thinking about converting...there are some things to be aware of. Mainly, '91-'93 was a breed all its own. Significant changes were made in '94 and again in '95. Early force motor was different and required periodic cleaning that was controlled by the PCM (Powertrain Control Module, aka "the computer"). AFAIK, the only GM PCM that can do this is 16147060 that came in '91-'93 2500/3500 trucks that had 4L80e. '7060 works fine and is tunable, but does not have the support from the tuner crowd that later PCM's have, specifically the 16197427 that came in later heavy duty trucks AND many many half tons since it was also used with the 4L60e tranny. In '94 they changed the force motor to a Holley design that did not require the periodic cleaning. This one may be the sweet spot for square 4L80e conversions since I think it was the last year of the solid style shift linkage - in '95 sounds like they went to a cable linkage that requires some mods to either tranny or linkage for compatibility with our trucks. Whatever you do make sure to get a control module (OEM or aftermarket) that is fully compatible with the year tranny you're using. I have no idea if the aftermarket control modules will work with the early tranny and do the cleaning, I'm guessing not.

I was told to get one that is 96+ as they were stronger and had resolved the problems the early ones had, guess this is one of the issues. Did you find a descent timing table or just make your own?

 

[yevgenievich]

Also on deacceleration, there are values for shutting off fuel. I wonder if ecm is getting in to parameters for fuel shut off then triggers stall recovery and goes back and forth.

 

[Daveo91Burb]

I was told to get one that is 96+ as they were stronger and had resolved the problems the early ones had, guess this is one of the issues. Did you find a descent timing table or just make your own?

Yep, early 80e's definitely have a few issues. Another one is that there's no good way to incorporate wideband O2 since the '7060 doesn't have any available 0-5v inputs. Later PCMs had a feedback EGR system that was 0-5v so you could eliminate EGR and then have an input for wideband. I did invest in a WB and have it installed, but I don't have the data output connected to anything - it's purely me looking at the gauge and comparing that with what's happening at the moment. It definitely helps - I can see the gauge pegging lean like fuel is getting completely shut off when it's at the low end of one of the cycles described above -- but combined with PCM data would be much more useful. Moates has a data logging device called the APU1 that will let me combine the two and then output to a laptop with TunerPro, but it's over $300 and I haven't pulled the trigger yet.

Timing table is pretty much stock vortec 350. Plan is to play with it more, but I've been spending time with fuel tables first and still trying to resolve all the other issues. It's conservative for sure, knock counts are low, so eventually I'll try and get some more timing in some areas.

 

[Daveo91Burb]

Also on deacceleration, there are values for shutting off fuel. I wonder if ecm is getting in to parameters for fuel shut off then triggers stall recovery and goes back and forth.

Yep, I've messed with DFCO settings, but am going to play with them some more. The weird thing is my data logs show that DFCO seems to be NEVER triggering so I don't think it's set right but I also am not sure it's going to help. There also might be issues with how the definition (.xdf) files was set up/hacked years ago. Perhaps they got some of the addresses wrong - there's another field called "Vehicle Moving" that ALWAYS shows "yes" even when at a dead stop. I don't know if that's just a problem with the file or maybe it's a real problem that is actually causing or contributing to my issues. VSS?

I'd actually like your stock .bin if you don't mind. You can find those online, but there's really no way to tell if someone has messed with the posted file. I've found some mislabled files and actually ran a bin in my PCM that was labeled for a 350, but was actually for a 454. I'll PM you my email.

 

[yevgenievich]

Might be moving/not moving related, but early ecm does use three speed sensors if 4wd. Not sure on exact arrangement, but two in the trans and one in the transfer case. Odd things happen when one fails.

Yep, I've messed with DFCO settings, but am going to play with them some more. The weird thing is my data logs show that DFCO seems to be NEVER triggering so I don't think it's set right but I also am not sure it's going to help. There also might be issues with how the definition (.xdf) files was set up/hacked years ago. Perhaps they got some of the addresses wrong - there's another field called "Vehicle Moving" that ALWAYS shows "yes" even when at a dead stop. I don't know if that's just a problem with the file or maybe it's a real problem that is actually causing or contributing to my issues. VSS?

I'd actually like your stock .bin if you don't mind. You can find those online, but there's really no way to tell if someone has messed with the posted file. I've found some mislabled files and actually ran a bin in my PCM that was labeled for a 350, but was actually for a 454. I'll PM you my email.