TBI 400
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Joined: Apr 2011
Posts: 25
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From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
TBI 400
have a question that i haven't found an answer to elsewhere. has anyone ever heard of putting a tbi fuel injection system on an old chevy 400sb? i can tell you it runs, but it won't time correctly nor will it idle. i'm thinking that the 350 computer and a set of 24lb/hr injectors aren't enough, but the 454 components seem to be too much... to the extent that the 454 parts make the 400 run so rich it looks and sounds like a deisel. with the 350 parts after the engine warms up it runs fine, but i don't have time to wait for it to warm up. 
Supreme Member
Joined: Jan 2011
Posts: 1,732
Likes: 4
Re: TBI 400
The stock tbi injectors are rated around 62lb/hr. The 24s your talking about are for a port inj. system like a tpi or lt1.
You either need to replace your fuel pressure regulator w/ an adjustable one or make yours adjustable, look on the web for that.
Check your fuel pressure, your pump might be weak, most guys replace tbi pumps w/ tpi pumps. With a tpi pump, more fuel is returned to the tank via the return line, so over pressurizing isn't a problem.
I don't know if your running an open element air cleaner, they are harder to run in cold weather, as some tbi system don't have an air sensor, even then it won't cure a cold stumble. You might have to run a stock air cleaner w/ a working hot air tube durnig the cold months.
You either need to replace your fuel pressure regulator w/ an adjustable one or make yours adjustable, look on the web for that.
Check your fuel pressure, your pump might be weak, most guys replace tbi pumps w/ tpi pumps. With a tpi pump, more fuel is returned to the tank via the return line, so over pressurizing isn't a problem.
I don't know if your running an open element air cleaner, they are harder to run in cold weather, as some tbi system don't have an air sensor, even then it won't cure a cold stumble. You might have to run a stock air cleaner w/ a working hot air tube durnig the cold months.
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Joined: Nov 2011
Posts: 398
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From: manitoba.
Car: 2002 ws6, 2011 sierra 6.2L 6 speed
Engine: ls1
Transmission: M6
Axle/Gears: 3:42's
Re: TBI 400
word. a little more fuel pressure via tpi pump and adjustable regulator may just be the ticket.
i always wondered how much low end torque a 400sb would make with swirl port heads and a tbi...
i always wondered how much low end torque a 400sb would make with swirl port heads and a tbi...
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
i can tell you, once the 400 is warmed up, i'm scared to think what more it could do with more than stock equipment... it already will break both tires free in all 5 gears 
. on a dyno the engine pushed 396hp and 415tq @ 5250rpm and 46000rpm respectively at 6500ft. 
on a side note, i've replaced both the fuel pump and installed a manual regulator... then took it back off and replaced a spring in the factory regulator, and it didn't change the cold issue. it runs better with the stock parts... 
i'm thinking i just need to get a new chip burned specifically for this engine, or put a holley avenger or hp efi computer in and be done with it. 
. on a dyno the engine pushed 396hp and 415tq @ 5250rpm and 46000rpm respectively at 6500ft. on a side note, i've replaced both the fuel pump and installed a manual regulator... then took it back off and replaced a spring in the factory regulator, and it didn't change the cold issue. it runs better with the stock parts... i'm thinking i just need to get a new chip burned specifically for this engine, or put a holley avenger or hp efi computer in and be done with it. Last edited by ryan.1e; Nov 27, 2011 at 11:29 AM.
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
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From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
made adjustments in 1 psi intervals from 10psi to 35psi (35 being far over anything neccessary for a tbi system) it ran progressively worse. all things considered, i am seriously considering it being a timing issue. going to look into some of the tuning applications.
Supreme Member
Joined: Jan 2011
Posts: 1,732
Likes: 4
Re: TBI 400
Tee up a vacuum gauge to the map sensor hose, I bet your cam is too wild for tbi. You'll want atleast 17" or more at idle. You might try the fitting at the brake boaster so you know its 100% manifold vacuum, not ported. You might also be able to advance the timing too, this'll help make more vacuum. These are really senstive to low vacuum & they usually run rich.
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Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
nothing says frustrating like having 22" of vacuum and completely unable to adjust the timing without killing the motor... past 4 degrees of advance it dies, less than 4 degrees of advance and vacuum falls off sharply and the engine dies before you get to 2 degrees... the timing is advanced/retarded by the computer based on throttle position, rpm, and knock sensor imput... the service code that is flashing is the basic diagnostic mode... i wonder if the knock sensor is causing the problem... too bad it wont even start without the bloody little bugger.
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Joined: Oct 2009
Posts: 676
Likes: 1
From: Pacific NW
Car: 89 K3500 Fleetside
Engine: RAT *tbi* EBL
Transmission: TH400
Axle/Gears: 3.73-Dana 60
Re: TBI 400
A 46mm throttle body to provide necessary air,
http://rvmorsemachine.com/product.htm
The ECM to run it,
http://www.dynamicefi.com/EBL_Flash.php
http://rvmorsemachine.com/product.htm
The ECM to run it,
http://www.dynamicefi.com/EBL_Flash.php
Junior Member
Joined: Dec 2005
Posts: 54
Likes: 0
From: Idaho
Car: 1978 Camaro
Engine: 385 Dual TBI, '7427
Transmission: 4L80E
Axle/Gears: 4.10, Posi
Re: TBI 400
If you have 22" of vacuum, then your cam is not the problem. I agree with Ronny, what injectors do you actually have? That number needs to be set correctly in the ECM/PCM. What computer are you running? If you have a relatively stock cam in it, which sounds like the case, then setting the injector specs correctly should get you really close. Also do not adjust the timing at the distributor. The engine timing should match the base timing in the chip.
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
Finally, finally, finally. thanks to a little (long effing time) searching for the right bloody gm truck, i have a 1974 400 sb chevy running a stock style throttle body fuel injection system. after finding the computer and injectors from a 1990 gmc seirra 3500 with a 454 and a manual tranni, i can focus on the paint. can't wait to actually get this car out on a section of road longer, straighter, and paved to see what it can do.
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
Finally, finally, finally. thanks to a little (long effing time) searching for the right bloody gm truck, i have a 1974 400 sb chevy running a stock style throttle body fuel injection system. after finding the computer and injectors from a 1990 gmc seirra 3500 with a 454 and a manual tranni, i can focus on the paint. can't wait to actually get this car out on a section of road longer, straighter, and paved to see what it can do.
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
And a nice Saturday for it to snow it was. Maybe tomarrow will work out to play around outside.
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Joined: Oct 2002
Posts: 1,096
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From: Idaho
Re: TBI 400
nothing says frustrating like having 22" of vacuum and completely unable to adjust the timing without killing the motor... past 4 degrees of advance it dies, less than 4 degrees of advance and vacuum falls off sharply and the engine dies before you get to 2 degrees... the timing is advanced/retarded by the computer based on throttle position, rpm, and knock sensor imput... the service code that is flashing is the basic diagnostic mode... i wonder if the knock sensor is causing the problem... too bad it wont even start without the bloody little bugger.
If you have a CEL well you need to fix that first...
Also never seen 24lb TBI injectors so need to find out what you really have? I don't have any 4.3L TBI injector numbers but this is a start...
5235279 - White / Green - 5Opph (overrated @ 55pph) - 5.0L / 305 Cars/Trucks
5235206 - Orange / Black - 61pph - 5.7L / 350 Cars/Trucks
17084327 - Yellow / Brown - 65pph - 5.7L / 350 Police Package
5235231 - Red / Blue - 80pph - 7.4L / 454 - 88-90
17084304 - Black / Blue - 76pph - 7.4L / 454 - 91-93
17104288 - Pink / Purple - 46pph @13psi - 7.4L / 454 - 94-95 *used @ 26-32psi for 67-72pph
Junior Member
Joined: Dec 2005
Posts: 54
Likes: 0
From: Idaho
Car: 1978 Camaro
Engine: 385 Dual TBI, '7427
Transmission: 4L80E
Axle/Gears: 4.10, Posi
Re: TBI 400
Computer from a '90 GMC w/manual trans will probably be a 1227747, which is ok, but you should look into swapping in a '6395 or '7427 from a '93 or '94 truck, much faster datastream and MANY more paramters to tune with.
Re: TBI 400
I've never seen a stock car with more than 19 inches of vacuum, how did you get 22 with a cammed motor? Something is wrong?
If you have a CEL well you need to fix that first...
Also never seen 24lb TBI injectors so need to find out what you really have? I don't have any 4.3L TBI injector numbers but this is a start...
5235279 - White / Green - 5Opph (overrated @ 55pph) - 5.0L / 305 Cars/Trucks
5235206 - Orange / Black - 61pph - 5.7L / 350 Cars/Trucks
17084327 - Yellow / Brown - 65pph - 5.7L / 350 Police Package
5235231 - Red / Blue - 80pph - 7.4L / 454 - 88-90
17084304 - Black / Blue - 76pph - 7.4L / 454 - 91-93
17104288 - Pink / Purple - 46pph @13psi - 7.4L / 454 - 94-95 *used @ 26-32psi for 67-72pph
If you have a CEL well you need to fix that first...
Also never seen 24lb TBI injectors so need to find out what you really have? I don't have any 4.3L TBI injector numbers but this is a start...
5235279 - White / Green - 5Opph (overrated @ 55pph) - 5.0L / 305 Cars/Trucks
5235206 - Orange / Black - 61pph - 5.7L / 350 Cars/Trucks
17084327 - Yellow / Brown - 65pph - 5.7L / 350 Police Package
5235231 - Red / Blue - 80pph - 7.4L / 454 - 88-90
17084304 - Black / Blue - 76pph - 7.4L / 454 - 91-93
17104288 - Pink / Purple - 46pph @13psi - 7.4L / 454 - 94-95 *used @ 26-32psi for 67-72pph
Supreme Member
Joined: Oct 2002
Posts: 1,096
Likes: 0
From: Idaho
Re: TBI 400
That is fantastic vacuum! Possible at sea level, I keep forgetting I am at 2000 feet so 19 - 19.5 is max here. 19 to 21 is possible on stock engines. Lower at higher elevation... Or your vacuum gauge a little off. His would be way off!
Point was 22 inches of vacuum from a big cammed motor is not right. 396 HP engine on dyno? No way he has 22 inches of vacuum... or 24lb injectors...
Last motor I did with 375 HP on Dyno was 80lb BB injectors set to 16 PSI to get enough fuel for WOT High RPM without going lean. Played with timing, min air setting, idle to 850 and got 15 inches vacuum at idle.
Also are you disconnecting timing set wire before setting timing? Has to be dis connected and with big cam 4 degrees should be fine, but then must put that amount back in Initial Timing setting in bin file or you will have to much timing at top. Intial timing in stock bin is set to 0.
That will also set a code, clear codes, start engine.
It is a lot of work to tune TBI system for big cam engine. No way it will ever run good on stock bin...
Point was 22 inches of vacuum from a big cammed motor is not right. 396 HP engine on dyno? No way he has 22 inches of vacuum... or 24lb injectors...
Last motor I did with 375 HP on Dyno was 80lb BB injectors set to 16 PSI to get enough fuel for WOT High RPM without going lean. Played with timing, min air setting, idle to 850 and got 15 inches vacuum at idle.
Also are you disconnecting timing set wire before setting timing? Has to be dis connected and with big cam 4 degrees should be fine, but then must put that amount back in Initial Timing setting in bin file or you will have to much timing at top. Intial timing in stock bin is set to 0.
That will also set a code, clear codes, start engine.
It is a lot of work to tune TBI system for big cam engine. No way it will ever run good on stock bin...
Re: TBI 400
im thinking his is a little off. i think he put in the wrong number or he is taking vacuum while at high idle but i still dont see it.
and yes sir i am at sea level. and the car runs great as well. and it darn well better with all the work i have done on it.
and yes sir i am at sea level. and the car runs great as well. and it darn well better with all the work i have done on it.
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
i started out to see if it would work, i'm pleased to say that with a few of y'alls' help it does, now it's time to get serious and do it right. post some pictures when i get around to it.
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
btw one92rs, are those actual vette rims or aftermarket knockoffs? if real, did you have any fitment or clearance issues?
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
That is fantastic vacuum! Possible at sea level, I keep forgetting I am at 2000 feet so 19 - 19.5 is max here. 19 to 21 is possible on stock engines. Lower at higher elevation... Or your vacuum gauge a little off. His would be way off!
Yeah, maybe next time i take the bloody muffler off and make sure the tach is working right before i play with timing or vacuum.
Point was 22 inches of vacuum from a big cammed motor is not right. 396 HP engine on dyno? No way he has 22 inches of vacuum... or 24lb injectors...
not a big cammed motor, and 39 was a typo, never caught that, thanks. 296 was the dyno measurement.
Last motor I did with 375 HP on Dyno was 80lb BB injectors set to 16 PSI to get enough fuel for WOT High RPM without going lean. Played with timing, min air setting, idle to 850 and got 15 inches vacuum at idle.
Also are you disconnecting timing set wire before setting timing? Has to be dis connected and with big cam 4 degrees should be fine, but then must put that amount back in Initial Timing setting in bin file or you will have to much timing at top. Intial timing in stock bin is set to 0.
yeah, again, i had the wire disconnected, the bad thing is with it connected the engine wouldn't start at the time.
That will also set a code, clear codes, start engine.
It is a lot of work to tune TBI system for big cam engine. No way it will ever run good on stock bin...
Yeah, maybe next time i take the bloody muffler off and make sure the tach is working right before i play with timing or vacuum.
Point was 22 inches of vacuum from a big cammed motor is not right. 396 HP engine on dyno? No way he has 22 inches of vacuum... or 24lb injectors...
not a big cammed motor, and 39 was a typo, never caught that, thanks. 296 was the dyno measurement.
Last motor I did with 375 HP on Dyno was 80lb BB injectors set to 16 PSI to get enough fuel for WOT High RPM without going lean. Played with timing, min air setting, idle to 850 and got 15 inches vacuum at idle.
Also are you disconnecting timing set wire before setting timing? Has to be dis connected and with big cam 4 degrees should be fine, but then must put that amount back in Initial Timing setting in bin file or you will have to much timing at top. Intial timing in stock bin is set to 0.
yeah, again, i had the wire disconnected, the bad thing is with it connected the engine wouldn't start at the time.
That will also set a code, clear codes, start engine.
It is a lot of work to tune TBI system for big cam engine. No way it will ever run good on stock bin...
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
New chips, new sensors, throttle body, wiring harness, fuel pump, headers, and no field problems/ work bs to deal with... and i have a 400sb running with "factory" tbi. only been really driving it for 2 days. will post part numbers, pics, and maybe a video later. all i can say is it's been a bitch, but these last two days have made it worth it. haha.
Re: TBI 400
my wheels are voxx misano wheels. they are not vette wheels. they were bought for an 04 gto so the offset is totally different. 1.5 spavers front and 1.25 rear.
Thread Starter
Junior Member
Joined: Apr 2011
Posts: 25
Likes: 0
From: Colorado Springs
Car: 1986 Camaro IROC Z-28
Engine: LS1
Transmission: t56
Axle/Gears: Stock Axle, 3.23 rear gears
Re: TBI 400
So, now that i have 1, found a cherry 1986 iroc, and 2 have come to own a ls1 and k-member for it, i am now selling my 90 rs with the 400 sbc and rebuilt t-5. anyone interested send me a PM. I am asking $4,000 for it, however any reasonable offer will be considered.
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