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Thread: Where can I go for harness modifications

  1. #16
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    I wouldn't even try running port injection on a TBI pump. If you don't want to do it all at once then change to a TPI pump first since the TBI system will still work fine with it.

    You could get adapters to connect -AN line to the front of the hard lines on the truck where the braided lines to the TBI start. Then, just go from there. I took the TPI connectors and braided TBI lines to a local hydraulic place and they crimped the ends onto the braided lines.

    As for the booster, it's a non-issue. The steel line is on the engine side and will be removed when you pull the TBI intake. So, just run a rubber hose from the booster to the vacuum port on the TPI intake.

  2. #17
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    Quote Originally Posted by lionelhutz View Post
    I wouldn't even try running port injection on a TBI pump. If you don't want to do it all at once then change to a TPI pump first since the TBI system will still work fine with it.

    You could get adapters to connect -AN line to the front of the hard lines on the truck where the braided lines to the TBI start. Then, just go from there. I took the TPI connectors and braided TBI lines to a local hydraulic place and they crimped the ends onto the braided lines.

    As for the booster, it's a non-issue. The steel line is on the engine side and will be removed when you pull the TBI intake. So, just run a rubber hose from the booster to the vacuum port on the TPI intake.
    Sweet info appreciate it. On the pump - could I just pick up a delco pump for a 96-98 vortec 5.7? I believe they run at 50 PSI? And I assume the system is return fuel injection?
    Do you happen to have pics of your modified fuel lines?

  3. #18
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    Quote Originally Posted by pro View Post
    Sweet thanks, this is awesome info. I always thought these proms were a burn once, throw away if done incorrectly. Like CD-ROMs.
    Do you happen to know if a the TBI 12psi fuel system is enough to get an MPFI motor started and idling? I understand cruising down the highway wont work, but what about just 1000rpm in the garage during initial tests.
    Also, you said you have converted many to MPFI. How did you solve the brake booster and fuel line issues? I cant see where the booster goes on my camaro, but it appears to be a port on the back, connected via rubber hose. Whereas the TBI of course is half metal line half rubber. A friend of mine converted his truck (NBS though) to hydroboost and loves it, but mentioned that even the slightest bit of contamination can cause steering issues.

    Throttle cables and cruise control doesnt seem like that big of a deal.
    For the conversions I've been a team member of, I've been the " Project Coordinator, PCM Setup, & Tuner" team member. The other team members took care of the "Nuts & Bolts" including the harness updates. For one of the conversions, I custom built a NEW MPFI harness for the "Nuts & Bolts" members to install.

    dave w

  4. #19
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    Would you guys recommend MAS or MAP? 89+ as a complete system is hard to find on ebay. Actually I cant find one at all, except for a couple of Vette ones, but I read somewhere that the vettes wouldnt work due to EGR issues.

  5. #20
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    Quote Originally Posted by pro View Post
    Sweet thanks, this is awesome info. I always thought these proms were a burn once, throw away if done incorrectly. Like CD-ROMs.
    Do you happen to know if a the TBI 12psi fuel system is enough to get an MPFI motor started and idling? I understand cruising down the highway wont work, but what about just 1000rpm in the garage during initial tests.
    Also, you said you have converted many to MPFI. How did you solve the brake booster and fuel line issues? I cant see where the booster goes on my camaro, but it appears to be a port on the back, connected via rubber hose. Whereas the TBI of course is half metal line half rubber. A friend of mine converted his truck (NBS though) to hydroboost and loves it, but mentioned that even the slightest bit of contamination can cause steering issues.

    Throttle cables and cruise control doesnt seem like that big of a deal.
    Getting vacuum to the booster is not an issue at all. Just unhook the hose from the brake booster check valve, throw the TBI metal line away and use bulk vacuum hose.

    I swapped my Express to hydroboost and love it.

    A TPI will not even attempt to start at TBI pressure.

    You will need a F or B car passenger side bracket for the compressor.

    Like I said though, have personally done the swap on an older G-van and it really was not worth it. The torque curve is wrong for a heavy truck. You loose torque in the 1,800-2,800 rpm range compared to a good dual plane and the runners will choke the engine at about 5,000. You can rev to 6,500 with a decent cam, good heads and speings but the power stops building at 5,000. The TPI did not offer any real fuel economy benifit either since it is batch fire.
    Last edited by Fast355; 4 Weeks Ago at 05:59 PM.

  6. #21
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    Quote Originally Posted by Fast355 View Post
    Getting vacuum to the booster is not an issue at all. Just unhook the hose from the brake booster check valve, throw the TBI metal line away and use bulk vacuum hose.

    I swapped my Express to hydroboost and love it.

    A TPI will not even attempt to start at TBI pressure.

    You will need a F or B car passenger side bracket for the compressor.

    Like I said though, have personally done the swap on an older G-van and it really was not worth it. The torque curve is wrong for a heavy truck. You loose torque in the 1,800-2,800 rpm range compared to a good dual plane and the runners will choke the engine at about 5,000. You can rev to 6,500 with a decent cam, good heads and speings but the power stops building at 5,000. The TPI did not offer any real fuel economy benifit either since it is batch fire.
    I havent puchased anything and am still thinking about it. I'll be out of service for a while soon anyway with plenty of time to study it anyway.
    The motor redlines at 4500. I rarely even leave past 3500 anyway. But how do long runners reduce torque?
    BTW, is this the TB you are talking about:
    http://www.ebay.com/itm/94-95-SILVER...-/201877793319
    What manifold would you recommend with it? I would need EGR for emissions ( i am in TX, euless as well )

    What options are there for supercharging? i remember back then there were prochargers, whipples, and wynjammer. i see wynjammer is still around and selling.
    Last edited by pro; 4 Weeks Ago at 06:44 PM.

  7. #22
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    Quote Originally Posted by pro View Post
    I havent puchased anything and am still thinking about it. I'll be out of service for a while soon anyway with plenty of time to study it anyway.
    The motor redlines at 4500. I rarely even leave past 3500 anyway. But how do long runners reduce torque?
    BTW, is this the TB you are talking about:
    http://www.ebay.com/itm/94-95-SILVER...-/201877793319
    What manifold would you recommend with it? I would need EGR for emissions ( i am in TX, euless as well )

    What options are there for supercharging? i remember back then there were prochargers, whipples, and wynjammer. i see wynjammer is still around and selling.
    The TPI runners are designed to resonate at a specific RPM and the torque production is strongest at that peak RPM. Happens to be 3,200 rpm on a stock runner TPI setup. The resonance waves actually detract from the cylinder charge in other areas. I put a 305 on the dyno with TBI and then with TPI. TPI should on paper work best on a 305 because that is what it was designed for. It lost signifigant amounts of torque in the RPM range I mentioned.

    If you are still under the emissions tests you will need a manifold that allows for EGR. The TBI heads work best under 5,000 rpm and are a good match with TPI but you will experience some low-end torque loss down where the stock torque converter stalls. I noticed the loss cruising in OD with the converter locked. It took more throttle going up hills like on 287 and would either unlock or downshift to hold speed much more often. I had a 700r4 with 3.08 gears and turned about 1,700 rpm @ 70 in my old 1983 G20 van. I had a 1989 Corvette TPI setup on my 1983 305 with a small cam and tri-y headers. It was using the TBI ECM in PFI mode. I later put a 350 Vortec followed by a 383 Vortec under a modified TPI setup with SLP runners.

    If you are not reving over 4,500 the stock TBI unit could actually serve you well. You can make 300+ HP from the stock unit running higher pressure or larger injectors without even blinking. The 454 TBI helps as you approach 320+ HP.

  8. #23
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    Quote Originally Posted by Fast355 View Post
    The TPI runners are designed to resonate at a specific RPM and the torque production is strongest at that peak RPM. Happens to be 3,200 rpm on a stock runner TPI setup. The resonance waves actually detract from the cylinder charge in other areas. I put a 305 on the dyno with TBI and then with TPI. TPI should on paper work best on a 305 because that is what it was designed for. It lost signifigant amounts of torque in the RPM range I mentioned.

    If you are still under the emissions tests you will need a manifold that allows for EGR. The TBI heads work best under 5,000 rpm and are a good match with TPI but you will experience some low-end torque loss down where the stock torque converter stalls. I noticed the loss cruising in OD with the converter locked. It took more throttle going up hills like on 287 and would either unlock or downshift to hold speed much more often. I had a 700r4 with 3.08 gears and turned about 1,700 rpm @ 70 in my old 1983 G20 van. I had a 1989 Corvette TPI setup on my 1983 305 with a small cam and tri-y headers. It was using the TBI ECM in PFI mode. I later put a 350 Vortec followed by a 383 Vortec under a modified TPI setup with SLP runners.

    If you are not reving over 4,500 the stock TBI unit could actually serve you well. You can make 300+ HP from the stock unit running higher pressure or larger injectors without even blinking. The 454 TBI helps as you approach 320+ HP.
    What manifold would you recommend?
    Also, I read there may be some fitment issues in terms of the butterflies opening. Did you come across that problem?
    300 HP just by an intake and TBI swap? Are you sure?
    BTW the only mods mechanically are electric fans, borla shorties and a 15 year old borla muffler. The cat is factory and I was told clogged. I bought new cats and mufflers a long time ago and just need to be installed. If any of that even makes a difference.

  9. #24
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    In the morning Ill go with the edelbrock 3704 and 454 tbi and install in a couple of weeks. If you can point me to any instructions on what needs to be burned to a chip that would be helpful. I figured this would be much easier since I have already removed the TB and intake so many times in the past (broken off heater core line, EGR port cleaning, intake leak, etc).
    Ill probably check out going to TPI as well though soon after this just to see what it's like. I dont think I mentioned but I put about 500 miles a year on the truck so its not like its a required vehicle. Its just something i screw around with when bored or want to learn something new. so I hope dave isnt going anywhere anytime soon. And actually since it seems so dam hard to find a complete SD TPI, i could just start finding individual parts and finally have an entire setup by the time Im done playing with a 454 TBI.

  10. #25
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    It really doesn't matter if it's a SD system or not. You just need the complete mechanical assembly and ideally enough of the harness to get the injector wires so you have those connectors and throttle body wires in case the connectors between the TBI throttle body and TPI throttle body are different. If you get an early one then you'd just throw away or re-sell the MAF stuff.

    Trying to piece together a complete TPI system down to finding every nut and bolt could nickel and dime you to death.

    The Edelbrock 3704 would have to be bored to accept the larger bore 454 TBI. You could also use a carb intake with the required EGR ports and then use an adapter plate for the TBI.
    Last edited by lionelhutz; 4 Weeks Ago at 07:00 AM.

  11. #26
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    Quote Originally Posted by lionelhutz View Post
    It really doesn't matter if it's a SD system or not. You just need the complete mechanical assembly and ideally enough of the harness to get the injector wires so you have those connectors and throttle body wires in case the connectors between the TBI throttle body and TPI throttle body are different. If you get an early one then you'd just throw away or re-sell the MAF stuff.

    Trying to piece together a complete TPI system down to finding every nut and bolt could nickel and dime you to death.

    The Edelbrock 3704 would have to be bored to accept the larger bore 454 TBI. You could also use a carb intake with the required EGR ports and then use an adapter plate for the TBI.
    The Holley Projection manifold used to be cheaper but requires a little rework to fit and a carb style EGR valve. It already has 2" bores and a wide sealing area that will seal correctly to a large IAC area 454 TBI.

    300-66 is the part number.
    Last edited by Fast355; 4 Weeks Ago at 07:29 AM.

  12. #27
    Super Moderator dave w's Avatar
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    Side by Side Holley / Edelbrock SBC TBI Intake Manifolds. Note the Edelbrock has been bored to accept the 454 throttle body with some radius work in the throttle bores to improve air flow.

    dave w
    Attached Images Attached Images

  13. #28
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    Quote Originally Posted by pro View Post
    What manifold would you recommend?
    Also, I read there may be some fitment issues in terms of the butterflies opening. Did you come across that problem?
    300 HP just by an intake and TBI swap? Are you sure?
    BTW the only mods mechanically are electric fans, borla shorties and a 15 year old borla muffler. The cat is factory and I was told clogged. I bought new cats and mufflers a long time ago and just need to be installed. If any of that even makes a difference.
    What I was saying is the fuel system is capable of that power. Not the factory long block.

    Go to A&B muffler in Hurst on pipeline across from Autozone and talk with Stephen Riley the owner. Tell him Chris sent you and he will get you set up thay exhaust very resonably.
    Last edited by Fast355; 4 Weeks Ago at 09:41 AM.

  14. #29
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    Quote Originally Posted by pro View Post
    In the morning Ill go with the edelbrock 3704 and 454 tbi and install in a couple of weeks. If you can point me to any instructions on what needs to be burned to a chip that would be helpful. I figured this would be much easier since I have already removed the TB and intake so many times in the past (broken off heater core line, EGR port cleaning, intake leak, etc).
    Ill probably check out going to TPI as well though soon after this just to see what it's like. I dont think I mentioned but I put about 500 miles a year on the truck so its not like its a required vehicle. Its just something i screw around with when bored or want to learn something new. so I hope dave isnt going anywhere anytime soon. And actually since it seems so dam hard to find a complete SD TPI, i could just start finding individual parts and finally have an entire setup by the time Im done playing with a 454 TBI.
    I still have all my GM EPROM tuning stuff if you need a hand dialing things in. I recently pulled it all out and am about to dial in a TPI swap on a 1987 Firebird. It has a 10:1 355 with Dart Iron Eagle 180s, a Hotcam, and headers. Ran well with a Q-jet but it will have driveability with the injection. He wanted the look of the TPI over the TBI although I told him it would ultimately cost him HP. My brother and the owner did most of the mechanical grunt work. Full suspension rebuild, EFI swap with my guidance, serpentine belt swap, a/c system rebuild, 4th gen fan swap, TH400 swap, and more.






  15. #30
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    Quote Originally Posted by lionelhutz View Post
    It really doesn't matter if it's a SD system or not. You just need the complete mechanical assembly and ideally enough of the harness to get the injector wires so you have those connectors and throttle body wires in case the connectors between the TBI throttle body and TPI throttle body are different. If you get an early one then you'd just throw away or re-sell the MAF stuff.

    Trying to piece together a complete TPI system down to finding every nut and bolt could nickel and dime you to death.

    The Edelbrock 3704 would have to be bored to accept the larger bore 454 TBI. You could also use a carb intake with the required EGR ports and then use an adapter plate for the TBI.
    So I just leave the MAP connector on my TBI harness disconnected? Will the computer not throw codes? How will it measure air?
    The reason why I ask is I was under the impression that 89 and newer TPI use MAP sensors right? My 92 has one mounted on the side, like this Vette does:
    http://www.ebay.com/itm/90-91-Corvet...-/382059624647
    But I cant find a single unit like the one my camaro (MAP on the side).
    Last edited by pro; 4 Weeks Ago at 11:09 AM.

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