What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

454 / tbi vacuum help

Dukem

Dukem

Registered Member
Joined
Feb 1, 2009
Posts
53
Reaction score
0
Location
Baton Rouge, La
I had a 454 w/ tbi out of a 87-88 1ton into my 73 blazer. I runs but idles high. I know that the break booster line is not in the right place. I got a new wiring harness that only controls what i need, tbi and alt. I need a pic of one with the vacuum lines in the right place. thanks

003.JPG

001.JPG
 
I have a 3/4ton 87 454 TBI.
I think that the large threaded hole on the front of the TBI unit goes to the Booster via a non return line.
The fitting where you have the blue cap is what feeds my EGR valve..
I will take some pics tomorrow.
 
The large fitting in the center of the tb is for the PVC valve. Either connect it to PVC or plug it.
Most likely the reason for the high idle.
The other plugged fittings are for EGR and Gas tank vapor system.
There should be a fitting on the back side of TB that plugs into your MAP sensor.
You need MAP for TBI to run right.
Large threaded hole in TB adapter is for a coolant line to heat up the TB base. Depending on where you live/drive you may need to hook it up to pervent icing.
Brake booster plugs into a fitting on the back of the intake manifold
 
Last edited:
Thunder - thanks, that explains a lot. living in south louisiana i don't think i will need the heater for the tbi. Just wondering will a aftermarket spacer work in its place? Thanks again for the info. Duke
 
Can't use just a spacer, you'll need an adapter. Assuming you use a stock GM "spread bore" intake, you need a spread bore carb to big block TBI adapter. Trans-dapt makes and sells them, just saw some on summitracing.com for just under $50.

No idea how this may affect things like throttle valve for transmissions or throttle cable.
 
I got all the vacuum problems fix and the idle came down. Just waiting for the parts store to open and pick up some hose for the transmission modulator. I think that i will have to change the intake manifold to get rid of the water heater tbi adapter, us less someone know different. Hopefully all will go well on its first real road test. thanks again for the knowledge and help.
 
Update - from what i gather an spacer/adapter is not made to take the place of the heater box that the tbi sits on. I will have to change the intake if I want to do away with that. the next problem i have is the timing. set it on tdc at zero w/ the correct wire disconnected at the dist. we it is plugged back the timing stays at zero. it does not move. bad OBD1 or dist?
 
Only problem I could see is with a 700R4, where the TV adjustment may get screwed up.

As long as the 454 has a spread bore manifold, that should be the one. AFAIK there were only two used stock, either a Q-jet manifold with adapter (early), or specific TBI/454 intake (late).

Looking at that option for my car, somewhere down the road. Need something as short as possible though for clearance in my case, trucks really don't matter. :)
 
In that case not really an issue I suppose, since the 350 kickdown isn't critical to its longevity, nor is it picky in adjustment. :)
 
If you don't want water going through the spacer just don't plumb any water to it. There is no need to remove the spacer or to even plug the holes. There was water that went in the front and came out the back. Sounds like you now have all your vacuum fittings covered.
 
Yeah - I don't have it piped in now, I just don't want any issues with it cracking down the road it you will.
 
You must log in or register to reply here.

Latest Posts

Top Bottom