I have a question about the Holley 670 cfm TBI unit. In my Jegs catalog, it says for '87-'89s. Mine is a '91. What are the differences between the '87-'89 and '90-'92 TBI units? Also, someone on this board once posted that you should use the stock injectors with the Holley TB, not the Holley injectors. Is this true, and if so why? Thanks.

 

Injectors- The Holley injectors are of notoriously poor quality. I'm not too sure where the problems lay, but I'm pretty sure it's got to do with the fuel spray. Duh
Since the first version of the injectors, they've come out/coming out with a new type thats supposed to solve the problems with the first type. NJSpeeder will know if the new injectors are being sold with the new units.

TB- As for the differences between the TBI units, I know that there is no difference between the stock rochester units. There might be an ECM difference corresponding to those years (in the trucks that is. Our ECM's went to the 746 in '89), tho.

 

I think the TPS was different.

My '92 has the little connector with the pin arranged in a "triangle". My friends '90 T/A has the TPS connector where the 3 pins are "in-line".

 

If the TPS is different, can I use my stock TPS with the Holley TB?

 

no, just get a different plug and rearrange the wires, the one on the holly is ajustable so you will kinda want to keep that one. not to mention i dont even think the stock one will bolt up because the bolts are in different positions.

 

over thire in that how hard to get xxx HP from a TBI, some one quoted that its cheaper to rebuild you old TBI rather then buy that holly. Well no one here quoted that it was on a web site.

 

I have a '90 and am using the Holley 670. The only problem I ran into was with the linkage, that is the pin for the throttle linkage is located on the reverse side(away from the TBI as opposed to the stock which is towards). Also there is only a hole for the cruise control, so you will need to find something to make it work. The Kick down cable only needs to be adjusted, which is really easy to do.
Also, I believe holley is actually using GM injectors (AC Delco) now, though I'm not 100% sure if that's for all application.
Oh yeah....I have the 305 model, 502-5, so it might make a difference, but I doubt it.

 

Yes,
The injectors are GM Delphi units. These have been used for about 2 years now.

I think the only difference is the TPS (connector style) and the pins on the throttle arm as mentioned.

I installed one on a 93 a couple of months ago and it works fine.

 

An easy test to make sure you hooked up the TPS sensor wires correctly is to flick the TPS sensor and NOT the throttle. There whould be a lot of fuel sprayed in instantly and the car will almost stall. If it's running super rich and when you flick the car doesn't stall...you might have the wires crossed. I had this problem when I first did the swap.
The newer Holley units are using the GM injectors. I believe you can tell they're holley if they have those black half sphere caps and the GM injectors don't have em. I don't know if this is accurate but it's just what I've noticed.
As far as boring and cleaning the stock TB...why? If you have NO money to spend on a new TB then yeah, porting and doing all those tricks to the stock TB is fine. If you need a lot of air then you NEED the 2" TB. Holley did a great job with the design and just so everyone understand the history...GM screwed Holley over with the TBI systems. GM contracted Holley to make the parts and do all the development then the General blew off Holley and went with Rochester for the actual production. Holley designed TBI, Rochester just built OEM. Pretty shady operation but I don't know all the exact details about what went on. All I know is that Holley is a company I trust and considering their 670cfm unit comes with injectors and an already adjustable fuel pressure regulator for only $300, that's a steal of a deal. It even comes with the IAC and TPS sensors.
To hook up the cruise control you'll need to go to the parts store and pick up a carb linkage bolt, they're in every car parts store just look around and make certain it has a lock washer!

 

How does the holley tb compare to stock? Also, would using the 350 tb give more air than the 305 model?

 

the 305 and 350 model are the same, the only difference is the injectors. You would probably only feel a difference with the Holley unit if you are pushing 300+ HP.

 

Not true. You NEED a Holley if you're pushing over 300hp as that is about the limit of the stock TBI. Regardless of what some say, the Holley 670 is worth it. I only had the typical mods (headers, high flow cat, flowmaster, cold air intake mod, msd) when I installed the Holley 670, and I felt a pretty descent SOTP gain. Yes, there are probably better ways to spend your money before buying the 670, but it does help. I don't have any dyno figures, you'll just have to take my word. Like I said before, I have the one for the 305 w/ 57lbs injectors. My guess is that the people who rag on the Holley are probably the ones who tried to use the one made for the 350 on a stock 305.
Also, people are going to say the Holley injectors will go bad. Well, Holley uses GM Delphi injectors now and have been for I believe the last 2 years.

 

I just bought a Holley 670cfm unit w/ portmatched Edelbrock base.... How do you get the TPS to work correctly since I'm swapping it on to a 90 motor?

Thanks,

-Timbo-

 

The part you are looking for is GM# 12116257.
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