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TBI guys, I have a few questions HELP!!

Discussion in 'The Garage' started by K5MONSTERCHEV, Jan 11, 2005.

  1. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    OK. Im pretty knowledgeable about computers and such, thats what I go to school for. However, when it comes to TBI, I payed verry little attention, espically how easy (or not) it is to swap. A guy came into work and asked if id swap TBI on to his blazer. I thought id do some research before I took on the job. So I turn to my fellow CK5 brothers!!

    He has a 72 blazer with a 406 small block and hes getting the TBI setup off a 87 blazer with a 350. Throttle body, Comp, harness, dist, no fuel pump.
    Heres my questions.

    1. Will the stock harness work? Or is it more like the harness out of the cars with TPI, which just dont work?

    2. Since it has a 406, this wont work, correct? The injectors will be too small, the comp will think its a 350, no good. Would it need a new chip?

    3. He said hed get a 4 to 2 BBL adapter for the Throttle body. Besides changing Dist, O2, fuel pump and ect. Is it pretty easy? (Sounds less time comsuming then TPI).

    If the stock harness wont work is it better to get an stand alone harness, like from Painless? I am not trying to make this my headache, so all help and info is GREATLY APPRECIATED, like always. Thanks in advance!
     
  2. Mastiff

    Mastiff 1/2 ton status Premium Member

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    Why is he changing the TBI? Is there something wrong with the one already on the truck? Either way you'll need to do some chip programming, but it's easier not to change the hardware.
     
  3. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    No no, hes putting it on his 72 blazer. Its carbed now.
     
  4. dirtwarrior17

    dirtwarrior17 Banned

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    Alright grab some food and a beer cause this is gonna be awhile

    Damn that chick is hot... my age too.
    o yeah....

    sorry about the post but this is all the info you'll need. Had to go through the same thing.

    I've been there and done that. If you take a stock 350 tbi which flows about 400cfm and put it on a 406, it'd be like putting a small 2bbl carb on there... won't work. It will idle and work at low rpms but will lean way out up top.

    I just got my reman 355 with all the hot rod bells and whistles in my 88 making over 400 hp. Didn't want a carb so I ended up with a holley 670 cfm 2bbl tbi and projection intake manifold with an accel high pressure fuel pump on it will all the stock sensors, harness, and ecm. Bigger injectors + higher fuel pressure/flow = more fuel. Holley says the 2bbl tbi will support 275 hp but thats because they want you to spend a grand on a 4bbl setup. I have friends who have had this tbi on 383s and made gobs of power with no fuel starvation. The injectors on the holley 2bbl are huge 85 pph(stock is about 20 pph) and if you add a high pressure fuel pump on the other end you should be gettin enough fuel to feed the beast but you may have to get some computer work done. The stock ecms can relearn fuel curves but the older they are the worse they get. If he wants a cheap tbi setup go with the holley 2bbl but if he has the money get a 4 bbl setup. YOu can find the 670 2bbls on ebay for cheap.

    AS for a stock tbi on a 406 ..... the injectors are WAY too small for that much fuel. The stock harness is fine as long as he buys a stock replacement tbi like the holley. If you are goin to use the stock ecm you might need a custom chip depend on the mods of the 406. Sorry about the long post but i spent 3 months figuring this out for my rig.

    I also tried the 4bbl to 2bbl adapter and they end up robbing air flow and power because the wholes from the adapter to the tbi don't line up completly so you get lop sided wholes. If he wants to do it right without fuel starvation he'll need a 4 bbl tbi with a manifold and a new ecm, or a 2 bbl setup with the stock ecm, a custom chip, fuel pump, and tbi intake manifold. Otherwise it won't make big numbers. If its a pure stock 406 besides being bored out he shouldn't have any problems with a 2bbl setup and a manifold.
    the adapter is not made to make hp.

    A tbi swap is pretty simple but im not sure about how e z the computer swap and harness will be. Should be a lot easier than tpi tho.

    I speak from trial and error but i have yet to get my 670 2bbl up to speed because it is not road legal and i still have to hook up a knock sensro to a 77 block. If you just bolt on the holley tbi and don't mod the fuel system or intake manifold then i would say holley is about right on the 275 hp rating but if you change the pump and the pressure then add an intake manifold and a custom chip it will support alot more.

    The formula for injector size to hp says the two 85 pph injectors will support a little over 360 hp but holley says its 275. Keep in mind that the 360 hp is without computer changes. but adding a high pressure fuel pump will make up for the difference. it is rated at 275 with the stock fuel pump pressure which is about 13. I put a 45 psi pump on there. Still have to try it out to see if it will support 400 hp but i bet with a custom chip it will support more than 400. I called holley a while ago and they said the hp rating is because of the stock computer settings so a chip will make a huge difference but if the motor is heavily modded you will want to get the ecm reflashed or get a custom chip. A custom chip is the way to go because some chips that you can buy straight out of a magazine actually make it run worse with the holley tbi. You will feel the custom chip in your wallet because they taylor it to your cam, comp ratio, air fuel,exhuast, and heads. Might want to call a few local efi shops too.
    Just my 2 cents ..... X 10000000
     
    Last edited: Jan 11, 2005
  5. grindkings

    grindkings 1/2 ton status

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    Sorry Not trying to highjack but how much did your custom chip cost. I think i';m gonna go through JET.
     
  6. S10K5

    S10K5 Registered Member

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    Hey, I have a couple of buddies that have had great luck with this company TBICHIPS.com. That’s who I'm using this next fall when I drop the new motor in. He is EXTREMELY knowledgeable, and his prices are excellent. He is also very quick about returning e-mails with questions. Just FYI
     
  7. dirtwarrior17

    dirtwarrior17 Banned

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    I haven't got mine yet but i am going through one of my local efi shops...full throttle performance. Will cost around 300 with dyno tuning. Thats the best way to do it. You can SEE exactly what the motor needs all laid out on a chart so they know exactly what to put in the chip.

    Superchips also just started a custom chip program where you tell them what cid you have and all your mods, duration, exhaust, heads, etc, etc, and they send you a chip. But the best way to do it is to find a good efi shop with a dyno and go through them. only way to know exactly what to put in the chip.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Besides doing it yourself. :)
     
  9. Mastiff

    Mastiff 1/2 ton status Premium Member

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    Sorry. :blush: I should have gotten my head out of my butt before I posted. Had a few distractions here at the time...

    Doing your own chips isn't that bad, and once you get a little comfortable, you aren't at the mercy of these businesses to get your truck running right. I'm highly skeptical that anyone can tune you properly without seeing the truck in person, or else iterating about 10 times (they send a chip, you send logged data, they send another, etc.). By the time you learn how to log data though, you're half way to programming anyway.
     
  10. dirtwarrior17

    dirtwarrior17 Banned

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    If you have the software then you can do it yourself but i thought it was $300 and if you have no labtop your out of luck.

    the whole point is to get it done right and not mess with it. If your putting heavy mods on then you should wait until you are done with them before you burn a new chip. If you burn you own chips you will either need to buy an air/fuel meter or get it dynoed which ends up costing you about 200 more than having a shop burn it, unless you burn a bunch of em. If you don't you run the risk on runnin the motor too lean which will make it run hot and damage parts or it will run fat and build up carbon deposites. My local shop has a deal on dyno pulls.... $50 bucks for 1 hour. Check timing, sensors, air/fuel, hp, torque, rpms, all at once in about an hour. plus your can see where your fuel curve needs more/less and then you can burn a chip accuratley. Or burn a bunch of em and take em all to the shop and see which one makes power. For 50 bucks why not get it where it should be?

    Superchips is the least accurate way to do it, then doing it yourself ,then having it dyno tested and burning one yourself or having one made from the dyno pulls.

    How much is the cheapest software and what do you need to burn a chip?:confused:
     
  11. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    Thanks everyone!! When I got my chip made, I just told em what I had, and they burned it, no problems! SO basically im gonna tell this guy its not gonna work. Between the TB adapter, the injectors and harness, Its not gonna be too easy. And like I said, I dont want to make it my headache. I just want somehting I can get done and not worry about "well now you need to change this and this, ect." forget that.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    You can get EVERYTHING to burn chips new for under $300.

    Air fuel meter is already part of the injection setups, and I think there are a ton of people that would disagree that dyno tuning is the best way to do things.

    There is a LOT of variance in dyno's, you'll find people that prefer track time to dyno time, so it's all preference. In any case, you can tune it without the dyno perfectly fine.
     
  13. dirtwarrior17

    dirtwarrior17 Banned

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    A chip is what controls the injections air/fuel and there is no way to see what a chip has done to the curve without one unless you buy an air fuel meter.

    The entire air/fuel ratio is controlled by the chip so yeah it is in injection systems but you still need a dyno or air/fuel meter to do it accuratly. I'm sure there's alot of people who say you don't need one but there is no way to be sure it's where it should be without a dyno or air fuel meter. your changing the air/fuel without actuactlly knowing what it is or where it was. Some people would rather save the 50 and take a chance. It's not just about the air fuel tho a dyno is uselfull system with a **** load of other functions besides air/fuel, hp and torque. recurve the distributor, find proper backpressure, power to weight ratio, i don't know the list goes on...

    Just saying without an air/fuel meter or a dyno its guesswork. 50 bucks and you kill about 10 birds with one stone.
     
  14. dirtwarrior17

    dirtwarrior17 Banned

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    It will work but he has to use a different tbi than a stock 350 setup. I have a bored out efi manifold but i doubt it would fit those heads. IF hes still interested in getting tbi he needs a manifold and more fuel and air. Bigger tbi.
     
  15. Mastiff

    Mastiff 1/2 ton status Premium Member

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    I'm not sure what distinction you are making between an O2 sensor and an air fuel meter. Almost everyone tunes using their O2 sensor. You can do better with a wideband O2 sensor, but you can get by with the narrowband that is an integral part of the factory stock TBI system.
     
  16. dirtwarrior17

    dirtwarrior17 Banned

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    An 02 senses oxygen in your exhaust.
    An air/fuel meter is a piece you buy just to check the air/fuel ratio at the carburator or tbi of a motor. doesn't come with the efi. Most mechanics will tell you your catalitic converter needs an air/fuel ratio of 14.7:1 for correct scavenging but will differ at higher rpms. when you change the chip it changes the ratio. There are alot of components that have to do with the air/fuel but like i said without getting a base from a dyno or air/fuel meter you are blindly changing the ratio. It may be fine at 2000 or 4400 rpm but then drop way off at 5000 and run lean or it could do the exact opposite and lose power from being rich... or you can get it close to optimum but it's almost impossible to say if its right or wrong just by listening to it. The only way to make the most power the safest with no guessing is ....... do i have to say it? You can get it to absolute optimum. ask anybody who has a dyno shop that you know or has done extensive dyno tuning. YOu can map the curve EXACTLY where you want it and where it should be for optimum power, not close.

    motors have varying fuel needs at different rpms and this is y you need a dyno. An air/fuel meter will help but with dyno you can look at the chart and say it leaned out at 3000 and change that part of the curve then leave the rest. If somebody can tune a motor by burning a chip from what they think is right then more power to em.... but it won't make as much hp as a dyno burned chip.
     
  17. Mastiff

    Mastiff 1/2 ton status Premium Member

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    But the O2 sensor measures AFR for you and it's already hooked into your pipes. If you log the data from your ECM, you will know where you're AFR stands all the time. I'm not saying a dyno is a bad idea, it'd be real handy to log data at specific RPM/MAP combos instead of accelerating all over town and getting pulled over by the cops. :grin:
     
  18. dirtwarrior17

    dirtwarrior17 Banned

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    I agree but in order to change the afr depending on the 02 sensor the computer needs to relearn a fuel map and the old systems are real bad at that.

    You never really know what it is unless you tap into the computer. It is possible to get it close yourself but unless you have a tach and a LOT of spare time i would go with a dyno.
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    You should stop posting about this now, and start reading over at thirdgen.org's diy prom board.

    It has nothing to do with the computer "learning"...it's all about actually changing the code the thing runs on.

    TBI ECM's are bad compared to other ECM's (slow) but in any case, YOU are the one that makes the changes, not the ECM.
     
  20. dirtwarrior17

    dirtwarrior17 Banned

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    Uh i no you are the one making the changes but when YOU are off the computer has to learn the correct fuel curve so it does have to do with learning. There is no way to tell the air fuel ratio with nothing but the software and a stock system... at least i haven't seen one.
     

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