[ckaram68]

Hey all, I've read some help posts about this, but still struggling. Total noob with this era (most eras frankly).

Bought a cleaned-up air cleaner base and replaced some of the parts. Mine weren't effectively connected and I'm trying to make it right.

1. One port on thermostatic air sensor goes to valve on shroud, I get that.
2. Where does second port go to? I've read port B on carb for manifold but I have a hose on that already?
3. Triangular device (fresh air modulator?)--where does it go?
4. "Looped" valve in far left of last pic that shows the whole air base. What does it do? Nothing in that spot when I bought the vehicle.

Here's some pics. Thanks for the guidance

[ckaram68]

This diagram says, "vacuum hose to intake manifold tee" but I don't see that on my intake.

[pippintook]

I have a 78 TA that had a W72 400 with 4spd. I turned into a stroker motor but kept most of the original parts and original appearance. The car is currently off the road - but I can offer some assistance.
.
First, I changed a few things, for example - the W72 qjet has a rear choke pull off - I removed the rear choke pull off (still have the pull off), I blocked the EGR valve (though all egr parts are there), I switched from hot air choke to electric choke.

For your questions

Q1: Where does second port go to?
A1: I think that is the air cleaner thermo switch - I am pretty sure I used carb port B - my vacuum hose (which could be original) fits this spot pretty good - not sure if this jives with the schematics ??

Q2: Triangular device (fresh air modulator?)--where does it go?
A2: I never knew what this part was...I saw a pic online from 77 Pontiac Service manual showing the air cleaner fresh air switch provides fresh air to the carb choke hot air stove port - I attached a pic. I have a 78 Pontiac manual so Id guess there should be info there

Q3: "Looped" valve in far left of last pic that shows the whole air base. What does it do?
A3: That is the SVB-TVS (Secondary Vacuum Break - Thermal Vacuum Switch), see attached pics from 78 pontiac service manual.

I think the vacuum schematics show you there are quite a few switches involved !

On 4 speeds 78 W72's, there is a 3 port DS-TVV switch - on auto W72s this appears to be a 2 port switch and is called DS-TVS, these switches impact distributor spark (DS). The switch is located on the side of the passenger head. I attached a pic of mine (not being used).

See attached pics for some more info

[pippintook]

see pics

[pippintook]

pic

[pippintook]

opps - file uploads limited to 300K max file size , so I had to make resolution very low, I guess I now cant read the text i copied into the pics

[ckaram68]

This is great stuff! I will pop the hood and review this weekend.

Thanks so much for all the effort.

[burd]

The manuals don’t show the color stripes though.

[pippintook]

Here are some updated pics where my text is bit easier to see. Again, my setup is not stock as do not have qjet secondary pulloff on the carb, EGR is blocked, using electric choke (therefore dont need to use parts for hot air choke - though I have most of them in place.
.
I was thinking I may try and put in place all the factory parts again (even though they would not really be operational).
.
This post is helping me to understand the factory vacuum routing and switches. The 4spd DS-TVV switch (called DS-TVS switch for autos) on the side of passenger cylinder head looks to be a kinda unique switch (I still have the original). The main switch on front of intake manifold (near thermostat housing) called EFE EGR TVV also looks to be a pretty unique switch. I need to check if I still have the original. You can see the factory routing also go to the charcoal cannister (I still have original of that on car).
.
To make your W72 look even more original, you can try and use all correct factory ignition wire parts and routings. I am pretty sure the factory service manual shows W72 ignition wire parts and routings. I tried this a number of years ago as I still had all the original parts.

[pippintook]

see pics

[pippintook]

burd - would you be able to post the color stripes info for a W72

[ckaram68]

Originally Posted by pippintook

Here are some updated pics where my text is bit easier to see. Again, my setup is not stock as do not have qjet secondary pulloff on the carb, EGR is blocked, using electric choke (therefore dont need to use parts for hot air choke - though I have most of them in place.
.
I was thinking I may try and put in place all the factory parts again (even though they would not really be operational).
.
This post is helping me to understand the factory vacuum routing and switches. The 4spd DS-TVV switch (called DS-TVS switch for autos) on the side of passenger cylinder head looks to be a kinda unique switch (I still have the original). The main switch on front of intake manifold (near thermostat housing) called EFE EGR TVV also looks to be a pretty unique switch. I need to check if I still have the original. You can see the factory routing also go to the charcoal cannister (I still have original of that on car).
.
To make your W72 look even more original, you can try and use all correct factory ignition wire parts and routings. I am pretty sure the factory service manual shows W72 ignition wire parts and routings. I tried this a number of years ago as I still had all the original parts.

Thanks again. I made a couple change per your pic and feedback. Trying to get "near stock". Doesn't have to be perfect, but I'd like the engine breathing/operating correctly.

May be in my head, but the replacement sensors and lines connected correctly seem to have the 'bird operating more consistently when fully warmed.