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Tech Editor's DeskProjects, papers, writings, thoughts, musings of our technical editor Joe Padavano. To begin with, he will be making threads and can approve posts to it if he wishes. This can be changed in the future if it does not work out well.
Can someone post the 1976 Assy manual vacuum diagram pages for a BBO 442 (77 does not exist or is super rare) with all power options?
My car has 403 AC PS PB Cruise PW PDL...There are a ton of hose connections on my project car most of them are not connected/plugged up. The sticker gets me only so far...
If anyone can take pics of their 77 hose connections/routing that could help me as well...thanks in advance.
Last edited by OLDScience; Oct 19, 2025 at 04:31 PM.
That is the correct vacuum hose routing diagram, as it is taken directly from the Chassis Service Manual, but note that the distributor is drawn incorrectly. The vacuum advance on an Olds distributor goes the other way due to the rotation direction. The distributor shown is for Chevy and Buick applications. All of the 1977 CSM diagrams are similarly incorrect, so this was just laziness as far as reusing the base artwork.
Some follow-up questions... the TACS and CTVS are both on the air cleaner?
Diagram is showing three ported vacuum switches DTVS, EGR/DTVS and the CTVS ..are these still sold on the aftermarket?
Also see a EGR TCV, does that sit on the radiator?
...and the DV DV...assuming that's a check valve?
I didn't see any vacuum ports on the compressor, and I also have a vacuum line for the cruise control
Let's back up a little, as I've just re-read your first post in this thread. First, your 403 is NOT a BBO. The BBO was dropped after the 1976 model year. The 403 is a small block Olds. Second, the diagram posted above with the A.I.R. system is for Calif emissions. The correct 49-state diagram is here: High altitude emissions is yet a third configuration. Which do you have? And third, at the risk of once again beating this dead horse, all of this info is in the 1977 Chassis Service Manual. Buy one if you plan to work on this car.
To your other questions, yes, both TACS (Thermostatic Air Cleaner Sensor) and CTVS (Choke Thermal Vacuum Switch) are attached to the air cleaner. The former is underneath, the latter sticks out from the side. The radiator isn't even shown in this diagram, it would be off screen to the right. The EGR-TVC mounts above the water pump, under the bypass tube from the t-stat housing. There is supposed to be a small sheet metal box cover over it. The DVDV (Distributor Vacuum Delay Valve) and DTVS (Distributor Thermal Vacuum Switch) are not used on 49-state cars, as shown in this drawing. The SAVM (Spark Advance Vacuum Modulator) replaces them and does not screw into the cooling jacket. Availability of new replacement parts for these will be hit-or-miss. There is virtually no demand for these nearly 50-year old part, so most replacement parts vendors have dropped them from their inventory long ago.
I've found a few OEM part numbers. The parts book does not use the same nomenclature as the CSM and the diagrams are too generic to tell what is what.
EGR-TVC is P/N 419459
Vac Delay Valve (DVDV?) is 561731
Valve, Vac Modulating (SAVM?) is 563494
Let's back up a little, as I've just re-read your first post in this thread. First, your 403 is NOT a BBO. The BBO was dropped after the 1976 model year. The 403 is a small block Olds. Second, the diagram posted above with the A.I.R. system is for Calif emissions. The correct 49-state diagram is here: High altitude emissions is yet a third configuration. Which do you have? And third, at the risk of once again beating this dead horse, all of this info is in the 1977 Chassis Service Manual. Buy one if you plan to work on this car.
I only asked for a BBO thinking that the 76 Assembly Manual vacuum routing would be similar to a 77 403 and prefer to see an assembly manual as it's better for how to route, pic references, etc.
I think I just have a 49 state. So I may have all of the ported vacuum switches as I just found the air cleaner and seems like the only thing I know for a fact I'm missing is the EGR valve...still have to find that EGR TCV. Maybe I'm missing seeing it...not sure yet
Thanks for the follow-up 49 state diagram...definitely helps me out
I only asked for a BBO thinking that the 76 Assembly Manual vacuum routing would be similar to a 77 403
Not even close
...still have to find that EGR TCV. Maybe I'm missing seeing it...not sure yet
Stand in front of the engine. Look at the thermostat housing. Look at the metal J-tube from the t-stat housing to the water pump. Look directly below that J-tube. If the EGR-TVC is intact. there will be a small sheet metal box on that "shelf" where the block casting number is. The EGR-TVC is under that cover. This photo is not a 403 and doesn't have the EGR-TVC, but it will be located right here.
Yeah, not there...and I just found out that it's not an original motor...looks like a BB0 70-72 (396021F). Funny carb is original , but somewhere down the line someone did an engine swap. I didn't even notice that as the engine bay is so large...Somewhat disappointed , but got it and another colonnade for a great price. The 403 probably spun a bearing and they tossed the motor. Also probably why the EGR TCV is not there.
Last edited by OLDScience; Oct 20, 2025 at 04:45 PM.
Yeah, not there...and I just found out that it's not an original motor...looks like a BB0 70-72 (396021F). Funny carb is original , but somewhere down the line someone did an engine swap. I didn't even notice that as the engine bay is so large...Somewhat disappointed , but got it and another colonnade for a great price. The 403 probably spun a bearing and they tossed the motor. Also probably why the EGR TCV is not there.
Post photos of the block, cylinder head, and intake casting numbers. Also, the block VIN derivative stamp.
Considering that your block has a 1974 VIN derivative stamp (second character is the model year), what do you think? And by the way, I have a sans-serif F block with a 1973 VIN derivative stamp, and yours is not the first 1974 that I've seen.
I have two ports on the top of the carburetor, one on the right (pass) side goes to the choke stove. Any idea of where the other one goes?
... or is the carb not correct?
here’s some advice. don’t try to make all those vac hoses work on your car which didn’t come with a 455 . Unless it’s a resto correct car and you need them, it’s to make it correct.
get rid of them all. except maybe the choke hot air tubes if you need the manual choke.
the car will run way better without all that pollution crap.
another thing , ignore Joe Pee. his purpose is to make you feel stupid.
That is the correct vacuum hose routing diagram, as it is taken directly from the Chassis Service Manual, but note that the distributor is drawn incorrectly. The vacuum advance on an Olds distributor goes the other way due to the rotation direction. The distributor shown is for Chevy and Buick applications. All of the 1977 CSM diagrams are similarly incorrect, so this was just laziness as far as reusing the base artwork.
you’re insufferable. it’s a generic drawing for Gods sakes…and why is your red arrow for the vac canister pointing in the same direction as the rotor rotation?
Ken, those ports are outside the air filter housing. One connects to the stove pipe and the other (orange cap) is the one I was asking about.
Yes, they draw air FROM the air cleaner, which is directly above the air horn. run a wire through each hole and you will see that it connects to the airflow from the air cleaner. The hot air choke uses a vacuum source on the carb to pull air in through the choke stove, this way only filtered air gets into the carb from the choke. The other port may have different uses depending on model year. In some years that was used to vent air from the emissions control hoses into the air cleaner.
A little off topic, but need to know if a 1/4 20 rod is the correct size for the carb to air cleaner hold down. It's a generic rod and seems to only thread about 1 1/2 turns into the carb. Before I cut it down to size, is that normal? I have some Quadrajets packed away so I cannot easily determine how far it should thread into the carb. I haven't used a Quadrajet in a long time, so memory has faded. I saw some of those studs with a shoulder on them but not sure what the factory used.