Hi Guys,

Some questions about TBI replacement:

Engine: 5.0L LO3 TBI (1988 Formula)

Does the Holley TBI 670 CFM replacement for GM trucks fits my engine? Holley says it is a bolt-on replacement for 5.0L Chevy and GM trucks.

If it doesn't fit my engine, does the Street Avenger 670 CFM Carburator would be a good thing to do?

Thanks

1988 Firebird Formula WS-6, T-5, bone stock!

 

The 670 street avenger would be way to much for your engine, especially if it is stock, as would the 670 tbi. Also, remember that the two barrel tbi is rated at 3"hg, where as the 4 barrel carb is rated at 1.5"hg, so the tbi actually flows less than the carb.

 

Huh? What would be the difference between the "Ultimate TBI" and a 670 Holley TBI?

Thanks

 

ultimate TBI, is porting out your stock TB, the Holley unit is a 2" bore TB.

 

First off, you do not have 2" bores on your intake so you would need a new intake manifold to use that tbi unit sufficiently. Second, if its stock, why do you need more air/fuel? What are you planning on gaining? I would go carb... i did b4.... tbi isnt the greatest system out there. Also... 670 cfm carb is MUCH different than a 670 cfm TBI. The carb is good for more horsepower than the tbi.


btw... is urs not working or what?

 

The reason I want a new TBI or Carb is that the current one is not working properly: it is always sticking when I push the gas pedal when idling. After it has been pushed, it then moves (open) freely.

I cleaned it many times and lubed it with Gunk, but it didn't work out properly. So I need to change it but I cant find junk yard replacement here in Quebec.

I am really pissed off by that TBI . I need something new asap: I am making wheel spins at every lights unless I slip the clutch...

Carb would be good, you think? Is it hard to change?

 

Your TBI is sticking because the throttle stop is mis-adjusted in such a way that the plates close completely and then bind in the bores. Your pressing on the fun-button hard enough breaks the plates clear of the bores, and off you roar.

If you increase the throttle stop screw setting just enough to prevent the trottles from fully closing, this problem will dissappear.

 

Great!

Ok, where is that screw? I assume it is on the TBI itself, isn't it?

Thanks very much

Charles

 

It's on the side of the TB that the cable hooks up to. That linkage has a bent tab that comes to rest on the throttle stop screw. Look at it; you'll see it.

 

Ok, found that screw.

I know it is a stupid question: there is a cap before the screw so I can't screw it, how do I remove that cap?

When this will be done I will not bother you again!

Thanks

Charles

 

IF you take a small punch and a hammer, punch in on one side of the cap, it will spin the cap sideways in the bore it's pressed into. You can then grab it with a pair of pliers and pull/pry it out.

If you don't have a SMALL punch, you can make do by improperly using a small screwdriver as a punch.

You can also drill the plug out. Any way you chose to do it, it's pretty easy. Your close to a smoothly operating throtte! Just remember to ONLY turn the screw barely enough to break the throttle plates free, and no more. You don't want to increase your idle speed artificially by cranking open the throttle blades. Good luck!

 

Thanks Tom

I do this tonight and post the results tomorrow

Thanks Again

Charles

 

Hi Guys,

I played with the throttle stop screw (you need a Torx T-20 bit) and it did solve part of the problem I had (stiff throttle pedal at initial push). But the idle is now at around 1000 rpm. I couldn’t go lower because the problem was still there. I don’t really care about that. But still, just like it did before, between each shifts, the engine still revs at around 1800 rpm. It just don’t go down. And when I drive at around 30 mph, I don’t even have to push on the throttle pedal, it is like cruise control, but no cruise on…. It is not because I played with the screw. It was like that even when the car was idling at 600-700 rpm.

Even then, when I had to stop for a light, the car was idling at 1500 rpm. I had to kick the pedal and then the idle would come back to 600-700 . It is les apparent now, because the idle is higher. This morning, when the car was cold, the pedal was a little stiff, and ok when hot. I am really pissed off by this situation.

What can I do with this *?%*((%?$/%*)*&??$%/$ TBI ?




Thanks

Charles

 

i had a problem with my throttle not closing complely, it stuck just before closing. unless i really slammed it shut. i ended up getting a throttle return spring for a carb and adding that, it gave it just enought tension for it to close all the say correctly.

 

If you have a vacuum leak, it'll cause your idle to hang and be too high. Check for that.

If you don't find any, you will either have to grind on the throttle blades to stop them from hanging up (beware of the risks first), or go ahead and replace the TB assembly. Sorry that didn't fix the prob, and I hope it's just a vac leak somewhere. Good luck.
-Tom

 

It sounds like he needs to rebush his throttle shaft.

 

Rebush? Sorry, but i am french canadian, I need an explanation

Ok, I am going in vacations for a while and will try to find a junk yard TBI.

Thanks for the informations guys

Charles

BTW, no vacuum leaks...

Dewey: what brand/type of spring did you used?

 

I had the same problem as far as the stuck throttle goes. I did what Tom suggested to you. I removed the throttle blades, lightly sanded them, and polished both the blades and bores. Just keep in mind that you're more or less just sanding down any rough spots, and DO NOT over do it. Mine now idles at a nice 650 rpm with no stick in the throttle.
Oh, and I think its a combination of having your idle set high and the idle air control that causes it to rev so high between shifts. Mine does it every now and then, and I hate it!!!!