Will a '93 C2500 454 (7.4L) tbi be the same as the earlier years? Please tell me the differences if it's different I just ordered one! I actually need just the housing with TPS and iac the injectors aren't important as I am building a homebrew mpfi project. For that matter the injectors that come with this tbi may be for sale...

I think I got a good price on the tbi unit.
Chris

 

Now I'm thinking I may swap to the TBI in the interim while I try to figure out the detials of my homebrew mpfi. I guess I'd need a 7747 ecm, harness, sensors and a fuel system that would put out ~15psi. Doesn't anyone know if the '93 tbi is the same as '88-92?

Thanks,
Chris

 

They are all the same. The only differences are the TPS sensors but they all bolt on the same way so it isn't difficult switching to a different style TPS. Keep in mind the 454 is a 2" TB and it's wider than the standard holley square bore. I don't know what you plan on doing so I'm just making sure you understand what is involved. You can either use a 1" adaptor from holley or even better, just make a standard adaptor plate and then grind a little off the wall of the square bore. The injector pod can be easlily blocked off with a small piece of metal cut from tin snips.
The IAC are all the same even though many a people think the Holley IACs that come with the 670cfm 2" TB has some strange wiring...it doesn't, it's a direct replacement so the weather plug just plugs right in.

 

Thanks for the info JPrevost. That's exactly what I needed. I currently run a Performer RPM on the 'Bu so I may do like you said: make an adaptor and grind the material that interferes with the 2" bores. So it's not that much material? I called PAW and their price for the Holley 17-45 is only 10.95 as reported here earlier. Of course the part # is on back order - but for that price it's worth it to wait - Summit wouldn't even match the price! Hood clearance isn't as much of an issue on the Malibu.

So do you think the plan of using the tbi for a tb, a 7730 ecm with harness, sensors & injectors, and the Holley intake/fuel rails would work (with an injection type fuel system)? I imagine a custom prom would be in order. I wonder if I should try to do the TBI swap first, but then that requires the 7747 ecm and harness.... decisions.

Thanks,
Chris

 

Chris, you're doing what I plan on doing in a couple years. I'm going to eventually go to tap the intake for injectors and use the TB to just control air flow. It's cheaper than TPI . Z28 boy (member) used a universal spread/square bore plate adaptor and when he went to the RPM intake from the performer he had to grind the sides a little to clear the throttle blades of the 2" unit. It isn't much and he's got pictures on his website, just search for him and the link to his site is in his sig.
Fastbroker is doing exactly the same thing as you. He's running a 350 on TBI but has 8 injectors waiting to be installed and run off of the 7730, it's in a jeep but that doesn't make a huge difference. He'll reply soon enough.

 

chris: are you selling the housing for the injectors that bolts to the throtle body. This is what i need. If so, how much. I don't really need injectors, just the housing, unless your are selling the 350 injectors. Thanks

 

I could be very interested in the injectors. I'll keep an eye on this string, let me know if they do become available.

 

I remember seeing in some magazine GM's original prototype for the TPI and do you know what the throttle body they had stuck on the end of the plenum looked exactly like? A tbi minus injectors.

I think I'm going with the Holley adaptor since I don't want to modify my (RPM) intake - I'll probably sell that intake to help offset the cost of the Holley intake/ fuel rails ($270+$200!: where can you get fuel rails for less??- surely there's a way for less than $200! I wonder if a stock TPI rail would work?) Also thanks for the tip about fastbroker, I emailed him.

I'm really considering swapping to the TBI for now - sort of "cutting my teeth" on TBI rather than going to full blown homebrew mpfi - I don't even have a way to burn custom chips - and the car we're talking about is my daily driver! The other consideration is there are some great U-Pull-It junkyards here in GA where I think I can get the 7747 ecm/harness/sensors for cheap. Will the 454 tbi's injectors work with a prom from a 350, or would I need a custom one?

gtrs-10: No I just bought a 454 tbi, but if you are working on a homebrew efi project tell us the details!

PaulD: not sure if the injectors will be for sale immediately, but I'll post as soon as they are.

Chris

 

actually i busted mine putting the fuel lines back on. about the home made mpfi. wouldn't it just be cheaper and easier to find a tpi set-up. i don't think that it is as simple as tapping the manifold. I would think that you would have to weld in some kind of mounts for the injectors. Plus you would want to have the proper angle for the injectors to spray in. don't mean to rain on your parade or anything

 

http://www.z28boy.cz28.com/intakes.htm

there is a page that i made up a while ago when i got my new intake. towards the bottom there are a few pics of the intake before and after the machining.

hope this helps...


-brian

 

Nope, it isn't as hard as it sounds, really. The only thing you need to be careful with is the fuel rail alignment. If the injectors aren't aligned properly the o-ring seals on the injectors might not seal.
TPI isn't the easy solution. Too many parts, too pricy, too expensive per part = not enough go for your dough.

 

If you go with the 454 TBI on a 350, you will need a new chip. That is exactly what I am considering doing. I just need to get the hardware as I can afford it and then go for a chip.

 

gtrs-10: My plans include the intake from the Holley Commander 950 system, p/n 9901-101-1, not a converted carb intake (although that's what the Holley intake is - but the CASTING was converted). Having said that there are several companies who will convert an intake - handy if you have a less popular powerplant: Pontiac, Buick, Mopar, etc,.

JPrevost: I agree, why swap to a LTR TPI and give up all the great engineering & performance that comes with a carb style intake? LTR TPI is a step back IMO.

PaulD: I think I may try to find someone who will burn a chip for me after I acquire the necessary .bin file.

The 454 tbi shipped this morning... my road to FI begins today.

Chris

 

Please, no, PLEASE, keep us (me) informed on how it goes. I have been wondering about the feasiblity of using either 454 injectors in the 350 pod and reprogramming or 454 entire TBI and reprogramming.
The advantage of the 350 TBI is that the manifold wouldn't have to be bored, nor would an adapter be necessary to clear the 2" throttle blades.

I'm really interested in how successful you turn out being. I am trying to fine tune a vacuum assisted fuel regulator with the intention of getting more fuel. I will post my progress and results.

 

UPS and the shipper droppped the ball but I finally got the tbi unit today. Two minor problems:

1) I don't have the right air cleaner stud, I grabbed one from an Astro but it isn't right - have to go back for one off of the 4.3L FI Monte I got the wiring harness from.

2) The throttle arm has no place to attach a TV cable. It has two funky barbs that look like an E-clip would attach to but that's it. Is it possible the C2500 was manual? Could I be that unlucky? Well I see two possible solutions - welding on an arm or adding a different throttle shaft. I wonder if a smaller tbi unit's shaft would work?

The good news is the bores are 2" and it looks like it came with a 1/4" injector spacer from the factory. For the price I paid I'm pleased. PaulD I'll keep the board posted and I'll let you know when the injectors are available. I'm going to look into modifying a stock 7747 bin and then have someone burn the chip for me (anyone? I'll pay).

Chris

 

Thanks.