part ID & smog pump removal

[496bb]

About to swap from TBI to carb (NO comments from the TBI lovers, you have no idea my situation and I don't care how well yours runs), trying to eliminate anything not needed. For now, I plan to remove the TBI adapter and run the factory manifold. Also would like to eliminate the smog pump - can I just leave the AIR tubes in place and sealed off? Down the road I will be swapping the intake and doing a cam and headers at the same time. I figure those tubes may be a real pain to get out to plug each of those 8 holes.

Trying to identify and understand the purpose of the part circled in red in this photo

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I thought this vacuum diaphragm was for cruise control on these trucks, but my truck does not have cruise control. Normal for it to be factory installed anyway? Or does it serve another purpose? Any harm in removing it and plugging off vacuum lines?

Also, can someone explain what the wire junction just above this part on the firewall is for? My truck also has some additional wiring tied in there for an old school brake controller (with a hardline from MC into cab and into the controller box). That controller will be coming out for a more modern version, gotta do a wheel cylinder, so gonna go ahead and put on new brake hoses and fresh fluid - so it's a good time to get rid of that old brake controller.

Thanks for any constructive help in advance!

 

[squaredeal91]

That part is a vacuum pod for cruise control.
Also don't throw away anything removed

 

[Ricko1966]

What TBI adapter are you talking g about. TBI has a TBI specific intake manifold. If you have an adapter,that would indicate someone put a carbureated engine into a TBI truck,which might explain the mystery of why you have a cruise control servo on a no cruise truck. And you can pinch those tube's shut at the manifold,you can weld them shut,you can pull them abd plug them, I guess for that matter you could cut them off short and drive plugs in them. Ball bearings come to mind.

 

[496bb]

1987 was first year for TBI, factory used an adapter plate and the same Qjet intake used previously.

 

[496bb]

That part is a vacuum pod for cruise control.
Also don't throw away anything removed

Oh no, taking lots of pics before, and everything in a box once removed. Leaving all the TBI wiring intact and tucked away neatly.

 

[Ricko1966]

1987 was first year for TBI, factory used an adapter plate and the same Qjet intake used previously.

Hmm you are right. Personally never saw a TBI that didn't have a TBI specific intake, thanks I learned something

 

[496bb]

My reading also indicates they didn't make a big block TBI specific intake til 91 maybe, or possibly not at all for Mark IV

Hmm you are right. Personally never saw a TBI that didn't have a TBI specific intake, thanks I learned something

My reading also indicates they didn't make a big block TBI specific intake til 91 maybe, or possibly not at all for Mark IV

 

[squaredeal91]

454 only used carb intake with adapter. The small blocks had a tbi intake. I always thought that was cool

 

[YakkoWarner]

454 only used carb intake with adapter. The small blocks had a tbi intake. I always thought that was cool

So a factory 1989 454 with TBI should actually have essentially a Q-jet intake with an adaptor plate? That could make my life a lot easier if it comes down to doing a TBI to Q-jet conversion.

And that part circled in red is absolutely the vaccum actuator for cruise control. If you REALLY don't want those components let me know, I have been trying to find the under-hood parts for 2 years (my Suburban had factory cruise-someone removed all the under-hood components but left all the in-cabin equipment in place).

 

[squaredeal91]

So a factory 1989 454 with TBI should actually have essentially a Q-jet intake with an adaptor plate? That could make my life a lot easier if it comes down to doing a TBI to Q-jet conversion.

And that part circled in red is absolutely the vaccum actuator for cruise control. If you REALLY don't want those components let me know, I have been trying to find the under-hood parts for 2 years (my Suburban had factory cruise-someone removed all the under-hood components but left all the in-cabin equipment in place).

I have an adapter somewhere. They have water go through it with hoses I think.
But yes the earlier TBI Big Blocks had carb intake with an adapter. There about an inch or more in thickness.

 

[YakkoWarner]

I have an adapter somewhere. They have water go through it with hoses I think.
But yes the earlier TBI Big Blocks had carb intake with an adapter. There about an inch or more in thickness.

I'll be checking on that - if I do have that setup I'll be much closer switching to a carb than I expected to be.

 

[bucket]

Correct. TBI 454's didn't get a specific intake manifold until the '91 model year. The older ones are just a carb intake with an adapter.

 

[496bb]

I have an adapter somewhere. They have water go through it with hoses I think.
But yes the earlier TBI Big Blocks had carb intake with an adapter. There about an inch or more in thickness.

It does have coolant hoses, I'll try and remember to post a reference pic in case anyone needs it. Front hose goes into intake next to T-stat housing, I think the other ties into the back of the plate and comes from the top heater hose.

My plan is to photograph everything thoroughly and box all the TBI stuff up for now, leaving wiring connectors in place and zip tied neatly out of the way. Later on when I do an intake & cam swap and such I may end up going to a Sniper 2 or Aces or similar FI to have better tuning ability, maybe. Doubt I'll ever go back to the TBI, and don't plan on this Burb ever leaving!

Yakko, I am still trying to research and figure out the feasibility of adding cruise either with the Qjet. If I decide it's too much trouble I'll let you know. I'm still curious if this was common practice on a Custom Deluxe w/no cruise control. Really confident in the history and originality of this truck.

I know there are tons of folks that just love the TBI, but reality is several of the electronic replacement parts have a less than good percentage of coming to you working (too much Chinesium I guess). The system is not tuneable without a chip burn. Qjets get a bad rap alot, but if you know them and build them correctly they were really good and fairly fuel efficient. I have some resources for built ones and help tuning them.

 

[496bb]

I'll be checking on that - if I do have that setup I'll be much closer switching to a carb than I expected to be.

Lots of good youtube videos to help with this swap, pretty straightfoward. One I found that had a few bits that I particularly liked was "Best Damn Shop Around" channel. Instead of cutting the the fuel hardlines, he used some adapter fittings to another AN fitting and did not cut his factory hardlines. I'll def be using that tip so I can retain those lines intact. He gives part numbers from summit in the video.

 

[YakkoWarner]

At this point my main curiousity is involving the 454 TBI adaptor. If there really is a standard Q-jet intake under there, and you remove the adaptor - what are coolant lines for and how do you reroute them? Not cutting/modifying the fuel lines or wiring is certainly a plus, in case returning it to original configuration is desired. I am always a fan of not damaging any of the original equipment (across any vehicles I have) - sometimes previous owners do it before me (as in the case of the stereo wiring in my Surburban and we won't even discuss what I found in the current British car project) in which case I'll work with whats left and may have to continue using a not-exactly-right solution depending on how much of the original stuff is still present.