4 barrel throttle body with gm computer?

I have built a big block Olds motor that would be capable of about 450 horse power, if I can get enough flow thru the throttle body.

I am using the 454 chev throttle body. it is equipped with a 4l80e overdrive trans that is controlled by the computer. It is installed in a 74 chev 4x4 that i use for towing.

With the configuration i have now it pulls pretty well off the line but runs out of steam pretty quickly due to not enough flow thru the small tbi. It would run much stronger with the quadrajet carb, but I love the easy starts and throttle response with fuel injection.

Does anyone make a 4 barrel tbi that would hook up to the GM wiring harness?

While there are 4 bbl throttle bosdies out there, most of them seem to use less than desirable injectors and many seem to fail.

A friend of mine has made a few 4 bbl throttle bodies by cutting apart and welding some 2 bbl throttle bodies together.

He runs the injectors in series and requires no modifications to the ECM to drive them.

His personal car is a '71 Olds Cutlass with a pretty stout Olds in it, making north of 400 HP, and 500 Ft/lbs, he's also running a 4L80E. He is using the 16147060 PCM to run the show.

I would love to see that setup! Have you access to pictures or a way for me to contact him?

I have checked the ECM, it is a 16147060. Can someone modify a PROM for this ECM?

with that kind of motor, it would be wise to invest in your own PROM burner/emulator.

That motor is only going to tune if you learn to do it. You are not going to get a mail order chip to do anything more than run... even then this type engine or truck should be done on a dyno. You will need much time to get er done on the street. Even then you will find so more on a dyno. Wide band O2 sensor tuning is really the way to go.

The new Delphi injectors in the Holley 4 Barrel TBI are good but the old ones are fishing sinkers. Then you need to modify your ECM to run them properly.

I have tuned a 440 Mopar engine with a 454 TBI unit on the 7747 so yours should be better.

Tuning does not happen overnight. If you are not preparred (like me) when you start and don't have time? Find someone to hands on tune your car. Yours? Not a lot of comercail options in the country that would even try... I started learning these in 1987 when the first TBI truck came out.... did conversions for 10 years... had a built in chip tuner I worked for so never needed one then got 4 years into tuning on web and about 12 vehicles.... I learn something new each day.

Your TBI is probably running out of gas way before it runs out of air.

Have you recorded any data from the ECM? How about fuel presure? What injectors are in it? What's the cam specs @ .050 ?

If these guys help with your ECM tuning (I'm only experianced in old school EFI 7747) I would help you learn and tune that. It would end up being a great write up for a starter for others in future.

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Originally Posted by 4554x4

I would love to see that setup! Have you access to pictures or a way for me to contact him?

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I should be able to get some pictures. I know sometimes he's a bit reluctant to share some things with the general populous.

There is no easy way to get a hold of him, because as much as he loves EFI, he hates computers, I do his tuning for him now. lol.

He was running on a mail order tune from a popular TBI tuning company, but since he changed the cam over the winter his old tune was no where near right, it was a drastic change. A couple hours of street tune and it runs better than it ever has according to him.

He's using the same PCM as you are, so yes the tuning can be changed. I just typed a 9 instead of a 4 earlier in the PCM service number.

The best thing you can do is get some of the equipment to tune. The original PROM can be replaced with a new EEPROM, which makes changes easier and quicker to make, you can also use an Emulator to tune while the car is running, I find this to be the best method, since you get to see the changes in real time and not need to shut the vehicle down each time you want to make a change. The time saved pays for itself IMO.

I stand corrected they can be run in series, I knew that but not in Parrelell. The one I saw done fired and injector right front and left rear and so on. This may have worked with a simotanious four barrel but filled the rear throttle bores on his progressive linkage...

Yes, progressive linkage would also require progressive control of the secondary injectors.

Eaglemark, You have asked some good questions. I will research fuel pressure cam specs etc. I will need some equipment to record data. Where can I find this equipment Emulator etc?

Ant thought to running two tbis on a dual quad intake? I do have the intake manifold and it would look cool!

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Originally Posted by 4554x4

Where can I find this equipment Emulator etc?

Ant thought to running two tbis on a dual quad intake? I do have the intake manifold and it would look cool!

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As far as Emulators go, I feel if you can swing the cost the Moates APU1 is the cats meow. Does almost everything a average tuner would need.

Two TBIs on a Dual Quad would look something like my set up. It's do-able, just have to work through it. You can check out my thread for more info.

gregs78cam, I dig your setup! I like your adapter! I think I will do that instead of using the old school dual quad intake. I believe that my performer intake will flow better anyway.

Much of the info here is just what I need. It will be quite an education for me. This site rocks!

Thanks. A common plenum adapter is a little easier to make a single IAC work unless the the Dual Quad has both TBIs mounted to a single plenum. But a dual quad will make it easier to fit an air cleaner. In a truck you should have plenty of room to do any type of air cleaner setup you like. There are pros and cons. To make mine work there were quite a few items that I had to machine and weld to make work. I will get some detailed pics today and update my thread with all the procedures and parts I had to make in order for it to work. I should have taken pics while I was making everything, but oh well. I didn't know if there would that much interest in how I did everything.

I know the 16197427 PCM has no problem running a pair of IACs. I haven't tested that with a 16147060 PCM though, but I can't see the IAC drivers being any different.

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Originally Posted by Six_Shooter

I know the 16197427 PCM has no problem running a pair of IACs. I haven't tested that with a 16147060 PCM though, but I can't see the IAC drivers being any different.

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Perhaps I dont fully understand the statement, forgive me if I dont. Wouldnt it run just fine using only one IAC instead of both?
I picture splicing the injector wires together, using only one IAC and TPS.

I definately have much to learn. Would it be possible to have too much CFM available, like over carb'ing or would the programing take care of that?

In some applications dual IACs will work better to have more balanced flow to all cylinders. Take the Crossfire system that I have on my Grandfather's truck, with the way the TBs are laid out, using both IACs, just like when the system was new, works best.

In a system where the TBI is a single or dual unit more centrally located, you can usually get away with just one.

I mentioned it more to do with how people say you "can only run one IAC," which is simply not true.

Only one TPS would be needed in anycase.

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Originally Posted by 4554x4

Eaglemark, You have asked some good questions. I will research fuel pressure cam specs etc. I will need some equipment to record data. Where can I find this equipment Emulator etc?

Ant thought to running two tbis on a dual quad intake? I do have the intake manifold and it would look cool!

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It's been done and I have always liked the look. But duel quad intakes are high rpm type thing. But with EFI tuning they idle and run from idle up fine. Most high performance intakes like that have no hot air crossover to warm intake in winter so they are sluggish when cold. But I have found the hot air intake from headers to intake using the delvac valve from just about any GM car fixes that. No vacuum lines needed. Just put the flapper into a hot air from headers to intake and it will let hot air in when cold and turn off to let only cold air in when warm. Also prevents TBI icing when temps are like 35 degrees and high humidity... rushing air and evaporating gas casuse temps to drop and TBI ices up... It's a North Idaho canada type thing! :innocent2:

I have an AutoProm. It's the only emulater I have ever had and I can't find a reason to change. I do everything with TunerPro and can't find a reason to change. Guess when you get something that works you stick with it.

The AutoProm is also set up to burn the chip when your done. It also has circuts to wire in your Wide Band. So it's hard to beat considering it all works with TunerPro.

As far as emulating, burning, recording, chipping equiptment I would say look around Moates website. Cover what we do and more. Fair prices, great support. They always have whatever I need. Well once I bought a JimStim from another vendor because Moates doesn't carry them...

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Originally Posted by 4554x4

I definately have much to learn. Would it be possible to have too much CFM available, like over carb'ing or would the programing take care of that?

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To much CFM is hard to do with EFI since the fuel is controlled by ECM. What your talking about by overcarburating is you don't have enough air flow over venturies to suck out gas. with EFI gas is determined and injected. Cylinder still only takes in volume of air it can hold. So no you can't have to much CFM and cause that problem. With MPFI it's even elimanated because no air fuel mix in intake.

But you only need so much CFM and a duel quad intake with two SB TBI and your still about 1000 cfm. You can loose some bottom end response. I noticed this in off road EFI systems I do I like smaller CFM (throttle plates) because of the low end response. Your always looking to idle and blip throttle. Total precise throttle control. But for a street/strip I don't think you would notice it, or have any issues you could not tune out.

another issue with TBs that can flow massive amounts of air is that even the smallest amount of throttle can produce a significant difference in airflow, which can't really be worked around unless progressive linkage was used, but i have yet to see that on a EFI motor.

I'm pretty sure Holley four barrel TBI was progressive and simultaneous cause I had to change one from progressive to simotanious cause the rears were filling up at idle, then I just gave up on the old holley injectors. Toyota also has a progressive two barrel TBI but only one barrel has injector. But I understand what your saying... there's a point where you loose top end or you loose bottom end. But still not as bad as what he was talking about with over carburating. That is a gas problem, not an air problem... sortof... just not enough air forced over venturi to suck out gas cause the hole is to big for volume of air cylinder is sucking in. It's like a planes wing not causing lift because it's shaped wrong.

OK, when I was about your age I remember you could not only change jets in a carb (that's like VE) but you could change venturis as well. So that was like AE? Pump shot has also got to be increased with larger CFM.

I still don't think he can over CFM a BB Chevy unless he really tried to... it'd be the same thing as if he had two 1000 carbs on it. No it's not going to run well from idle to 3000 RPM. But then again if you have two 1000 CFM carbs chances are your cam is designed to idle at 2000 and power band starts at 3000 RPM.

Don't know his cam specs yet but just some quick figuring looks like 2 5.0 or 5.7L TBI units would fuel and air his big block quite nicely.

maybe progressive linkage isn't the term i want to use? been a long time since i've been around a carb/TBI. :doh:

i was thinking more along the lines of when near fully closed throttle plate, pushing down the throttle half an inch would open the butterflies from 0 to 10*, but near WOT that same half inch would produce a far greater difference than 10*.

???????????????????

Here is my cam specs. the cam is a Mondello, part #JM-18-20
0.488 lift intake, 0.496 lift exhaust, 260°/266° adv. lift intake/exhaust, 216°lift at .050 intake, 226° lift at .050 exhaust, 112° lobe seperation, 1000-5000 rpm range.

I am trying to find the specs on my fuel pump. No luck so far. It is for a tpi camero as I recall.

Those cam specs are considered max EFI capable. If you look at aftermarket EFI companies you will find near identical numbers, then bigger fees for tuning. In a big cubic inch motor easier. With a TPI pump and TBI injection you will have enough fuel! :jfj:

Well enough if you run 3/8th line both ways! There will be a lot of extra fuel at idle/low end and hardly any top end. Don't think you'll get by with 5/16th return as return presure will not be 0 PSI. When I did it return pressure was 3 PSI which rasies inlet by 3 PSI. Went to 3.8th return and all was well.

WOW, I should have checked this thread last night. Yes 2 IACs are possible and yes Crossfire had them, however the common problem with those is over time they may become out of synch with each other. So you just do an IAC reset and all's well. The other way around it is to run 1 or 2 IACs and use a 3/8 hardline to connect the plenum side of one to the plenum side of the other. This would of course be if you had two TBIs with no common plenum.

My cam is slightly larger than yours and it still runs great with TBI. Better in open loop than closed, but it may just need a little more work on the tune. I would be surprised if your 455? even needed any real tuning other than injector flow and idle speed set to your preferences. How much vacuum does your current setup pull on a gauge? 15" or better and it should be fine.

As far as having too much airflow potential - not a problem. With a carb, as stated earlier the vacuum signal, and flow past the venturi is what determines how much fuel is metered in. With EFI MAP, TPS, O2, CTS, etc is used by the ECM force feed the fuel to the engine. It really dosen't care how many CFM it will flow.

Fuel lines? I am running 3/8" supply and return, and have no problem feeding my 425hp 383. I would also suggest getting a pump assembly from '93+ Grand Am/Cavalier and using the entire bucket assembly to prevent fuel starvation from uphill/downhill, and off camber situations. Yes they are rated for less flow at higher pressure but it flows plenty for me at 13psi. You could probably fit your TPI pump right into it. I have a stock van style pump and pickup tube in my '74 Chevy Truck and it will stall under hard braking with less than half a tank in it. It will be getting a J-body bucket assembly when I can get another one from Pull and Save.

I remembered tonight that Rick (The guy with the 4bbl TBI) had said that a couple pictures of one of his 4 bbl TBIs were published to the web, so I did a quick serach.

I should be able to get some better pictures, but this is one of the first 4 bbl TBIs he built.

http://www.ssgm.com/daily_images/109210-72235.jpg

http://www.ssgm.com/daily_images/109210-72234.jpg

http://www.ssgm.com/news/aftermarket-fr ... 000199226/" onclick="window.open(this.href);return false;

See, I was initially thinking about something like that, but I didn't want to mess with getting the geometry right with the linkages. Looks like real nice work though.

Now that is some sweet work! :wtg:

Sometimes I think differently than others. I think my approach to a 4 barrel TBI would be similar to the Holley design. I would use an off-the-shelf 4 barrel throttle body and modify the GM injector pods? I really don't have the time to figure out the details. I think maybe some sand casting would be required to make a 4 barrel GM injector pod?

dave w

or you could buy the newer holley?

I've got an older holley four barrel here with the fishing sinkers COUGH injecotrs. I have not had time to see what it would take to put GM injectors in it...

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Originally Posted by Six_Shooter

I remembered tonight that Rick (The guy with the 4bbl TBI) had said that a couple pictures of one of his 4 bbl TBIs were published to the web, so I did a quick serach.

I should be able to get some better pictures, but this is one of the first 4 bbl TBIs he built.

http://www.ssgm.com/daily_images/109210-72235.jpg

http://www.ssgm.com/daily_images/109210-72234.jpg

http://www.ssgm.com/news/aftermarket-fr ... 000199226/" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

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That is some sweet work, on an torker manifold for an Olds! I like it!

i am in the middle of doing this four barrel tbi and i was reading this thread and saw where you all were talking about the linkage and the amount of air you get from just a little bit of pedal and was wondering if you all think i might have a problem with my 700r4 trans not getting enough line pressure to keep up with the engine RPM and power and would cause to burn up my clutch packs ?