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TPI Guys! 305tpi system on a 350 engine

Discussion in 'The Garage' started by primerk5, Mar 15, 2007.

  1. primerk5

    primerk5 1/2 ton status

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    Ok, I just got a wiring harness from an 88 iroc to go with my Tpi system that I have. For now I just want to use the 305 injectors and the 305 ECU I already have. What will this do? Will it run bad? A friend of mine said that it won't have as much top end power.
     
  2. resurrected_jimmy

    resurrected_jimmy 1/2 ton status

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    It will probably run allright. If the TPI systems are like the TBI systems for 305/350 then all you need is a new chip for the ECU
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    You may run the engine lean to the point of destruction.

    TPI doesn't have a way to keep your engine "safe" in certain conditions (open loop, and to a point acceleration or heavy loads) because it isn't watching the air/fuel ratio. That's preprogrammed in for a 305 in your case.

    Spark control, knock retard, injectors, and programming are ALL different for a 305 than a 350, that should tell you something.

    Not saying it won't work, but 383's with 350 injection stuff HAVE detonated to death, and have a look at the before/after AF ratio from burt4x4's dyno run:

    http://coloradok5.com/forums/showthread.php?t=163920&highlight=dyno

    His "before" AFR is exactly what happens when you run a poorly tuned injection setup on the wrong motor, IE 305 injection stuff on a 350. Believe me, you will *think* it runs great. But the before/after numbers there prove otherwise, and his comment was that it ran good before!

    You can buy Ford Motorsport injectors off Summit for about $250, but you'll still need the other components correct to run right.

    Don't forget, a 305 and 350 have entirely different timing requirements and knock signature, and that is ALL dealt with via the ECM (PROM actually) and ESC/knock sensor setup.
     
  4. primerk5

    primerk5 1/2 ton status

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    dern it, Looks like 350 injectors and prom here I come!
     
  5. primerk5

    primerk5 1/2 ton status

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    What might happen if I change the prom and not the injectors?
     
  6. thedrip

    thedrip 1/2 ton status

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    It still runs the chance of going lean. Also the 305 TPI is slightly different from the 350 TPI unit, the runners are sized slightly differently. a 305TPI on a 350TPI just won't make power above 4000-4500 rpm, no matter what prom/injectors you have. Not that a stock 350 makes a whole lot over 4500 anyway.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    You would be just as bad off...the injectors still only flow what they are rated, (19lb/hr for 305, 22lb/hr for 350, stock) so it gets a little complicated.

    Say GM figured for the 350 that at 22lb/hr, idle, the injector needs to stay open for 1 millisecond. (making up numbers here, but in practice this is how it works) Well, if GM makes a proportionally smaller injector (19lb/hr) and puts it on a smaller engine, the amount of "on" time for the injector does not need to change. So the injector flow rate hasn't changed, and unless the PROM keeps the injector open longer (which wouldn't be necessary with larger injectors, which is why they run them) the amount of fuel won't change, at least not significantly.

    The only way to "artificially" change the amount of fuel the injector flows is to crank up the fuel pressure. But fuel pressure is a global change in the system. It affects everything, closed and open loop, and unless the PROM is changed to use the higher fuel pressure/additional fuel delivery to calculate everything, the calibration is still going to be wrong. It may be ok in some spots, lean in others, rich in another, or rich all over, etc. No way you can possibly know except watch what the ECm is doing by datalogging/dyno time.

    You see that on Burt4x4's motor. AFR was about 14.7:1 off idle, but went super lean very quickly, and stayed there.

    If you plan on keeping the setup, just save up for the new injectors, tuning stuff, and do it right the first time. I had two bad injectors when I finally replaced mine, and without spending money on having them tested, there'd be no way to know if they were working correctly.

    You've already got the wrong injectors, just replace them with brand new ones, that will work for your intended application. It's better to go too big than too small, as long as you aren't wildly over on the lb/hr rating, they can be controlled via PROM tuning. The bigger they get the harder they are to accurately control, especially if the engine can't use the added flow.

    305 hardware (runners/intake/plenum) is no different than the 350 hardware. This is why TPI is a bit of a dog on anything larger than the 305, because that's what the setup was designed for.
     
  8. primerk5

    primerk5 1/2 ton status

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    I really appreciate all of your guys input. I'm gonna get the stock replacement 5.7 injectors just so everything is correct. When I first got all of this stuff the proms were everywhere brand new on E-bay now I don't see them Guess I'll have to watch for a little while. They were about 75 bucks +shipping.

    Thanks again.
     
  9. Blazer79

    Blazer79 1/2 ton status

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    I just finished swapping a 350 into my 305 camaro and changed from MAF to MAP as well. I used f*rd EVO 24# injectors. I'm starting to learn what to change when burning my own chips. One of the constants is the injector size, so theorically you can use the 305 injectors if you put 19# in this field. The computer would then adjust the pulse width accordingly. The thing is, I don't think the 19# injectors from the 305 can handle such a large pulse width. Others have claimed to have accomplished this by increasing fuel pressure and making the computer think it has 24# injectors. Check out http://www.thirdgen.org for more info on TPI.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    I think you'll find the stock 350 injectors are probably a lot more expensive than the Ford ones.

    Ford ones are what I've got, (except 24lb/hr, not 22) for the price they can't be beat. I wouldn't even contemplate used injectors unless they are very low mileage and that can be proven.

    Stay away from Accel injectors. Read up on those at thirdgen if you wish. :)
     
  11. twodollars

    twodollars Registered Member

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    For new, the ford's are the way to go. I also just picked up a set of GTO injectors that worked out to about 24lb. They fit with a little massaging, and work fine. Whatever you do, just start with the fuel pressure set high to protect your engine at WOT, and then start going down.
     
  12. primerk5

    primerk5 1/2 ton status

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    Ok, I'm going to do some research on the Ford injectors. What are the chances that the injectors out of a caprice classic wagon (TPI non runner type) are the same. I crossed referenced the part numbers and they aren't. I'm beginning to think that the difference is just the amount of fuel flow/pressure. Especially since the one guy said he used GTO injectors. I can get an intake that has them in it for 20 bucks. But then again you don't know if they are any good or not. I'm definatly changing them now. Just don't know what to.

    Heres a new question.

    I just bought my wiring harness off e-bay. Its supposed to be in really good shape. I'm planning on retrofitting a stock harness out of a 88 I-Roc to my truck. I have a few books on doing TPI swaps. Of course they all suggest to buy the painless kit. I just could use that money elsewhere on my truck.

    How many of you guys have used a stock car harness. Was it difficult. What was the setbacks??

    Thanks again.
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    I've got a car harness. Whatever year the setup is you are transplanting, buy the wiring and service manual. (either new helms, $$$, or find one on ebay, hint: search for firebird/pontiac instead of camaro/chevrolet)

    The harness is daunting when you first look at it, the wiring manual will make your life SO much easier. IIRC in the tech section (electrical?) of thirdgen.org there are the '85 and '86 wiring manuals. Harder to deal with than the manual, but useable. GM stayed pretty similar from '86-89 on the TPI setups wiring-wise.

    Forget Painless. Some have no problems, and yet I still see some stupid mistakes made in the construction of their harnesses. For the price they should be identical to the GM stuff, so you can use the factory service/wiring manuals.

    The problem with some of the injectors is the length and the way they lock to the fuel rail. The stock ones and Fords are the ONLY ones I'm aware of that are essentially "bolt-in".

    Same username on thirdgen, I did a ford injector tech thread with some measurements and so on. Probably have the part number (although you'll want 22lb/hr unless you intend to do some mods to the motor from stock) and you can find the o-ring kit PN on thirdgen.org as well.

    Don't know when GM changed the fuel pressure, if ever. I'll say it one more time: Unless you plan to spend the $75+ to have used injectors tested, don't waste your money on them. Almost halfway to new Ford ones if used ones cost you even $20.

    Try to save money now, spend it later. And spend more time. You get the setup together with used injectors, it doesn't run right, or at all. Is it because of the injectors that you don't know for certain are good?
     
  14. primerk5

    primerk5 1/2 ton status

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    What would the ford injectors have come in originally?(make/model/year) I just found out a friend of mine has a connection/child hood friend that is an fuel injector engineer at some place where they make injectors. Maybe able to get them even cheaper. Though, His friend said that his company Dosen't list them anymore for the model I have. He said he needs to look at the design to see what he can find in comparison. If there is something else that might work I want to tell him to look for that also. Thats why I was wondering what model ford would have gotten those injectors you'r telling me about.
     
  15. primerk5

    primerk5 1/2 ton status

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    BTW. The price on those injectors has gone up 309.95 now at summit.

    They'll be what stock GM replacements are soon. HAHA
     
  16. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Ford SHO V6s use 22 lb/h pink top SVO injectors :)
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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  18. 54inches

    54inches 1/2 ton status

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    The 305 and 350 tpi are EXACTLY the same.

    When I had my Camaro and a Vette. system, I checked both systems and they are exactly the same. When you order runners from GM they are the same. The injectors are different on some years, as are the systems, MAF/Speed Density and 90-92 do NOT have an 9th injector. My 305 was a 92.

    I had the uppers and lowers ported and basically cleaned up, the TB gasket matched and cleaned up, had the MAT sensor moved closer to the front of the air intake, and added a Adjustable Fuel Pressure Regulator.

    I slapped my 305 TPI system and a built 350 with Al. Vette heads and it ran like a scalded dog.

    Now I never changed the ecm/chip or the injectors. I think I had a ton of power left and injectors should have been my next upgrade.

    .02
     
  19. primerk5

    primerk5 1/2 ton status

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    See I've heard stuff like this before. Thats why I was wondering if it could be done without harm to a 350. Hopefully that friend of mine can come up with those injectors and I can get this put together right.
     
  20. 54inches

    54inches 1/2 ton status

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    Now with that said I was swapping from one tpi motor to another and it was built FOR a Tuned Port Injection. You need to check the specs on the engine that you are putting the injection on.
     

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