What is this thing and does it create vacuum?

[84-460-Project]

If the only thing w/o manifold vacuum is the HVAC system just plug it into the manifold vacuum port on the front driver's side of the carb, as shown in Figure 1 in the Edelbrock installation manual. But, as was said, you do need the check valve/tee and vacuum reservoir shown in the Vacuum Systems pics or your HVAC system will default to Defrost when the vacuum goes away with heavy throttle.

As for the ones on the thermostat housing, they are temperature controlled and were part of a complex system to provide vacuum for various emissions systems at specific temps. Since you have an aftermarket carb and no belt on the AIR pump I'm guessing you aren't worried about emissions. In that case I would remove those valves and plug the holes with pipe fittings. Then I'd set my vacuum advance up with ported vacuum from the timed port on the Edelbrock carb, which is the port on the front passenger's side.

And if you aren't using the thermactor system we can talk about how to remove it.

We are resurrecting this truck and learning about it at the same time. The previous owner(s) made some mods and decision that we get the joy of finding out about when fixing specific issues.

I'd like to get this truck back to stock, but in the short term the Thermactor system will stay offline. I might put it back together when I pull the motor and rebuild it, but maybe not.

I'll try the the manifold vacuum to HVAC. Have you tried this work around with success?

So ported vacuum (vacuum at idle) is vacuum all the time and manifold vacuum (timed vacuum) is only when the engine is accelerating?

This forum is awesome! I've struggled trying to figure this out on my own for a while.

After we get this fixed, we need to fix the spedo (drive gear and driven gear at the transfer case), time and tune, fit a holley carb (so we have an extra standing by), replace the power steering gear box and steering linkage bushings. Then hook up a trailer and start pulling stuff.

Should be fun.

 

 

[ArdWrknTrk]

If the only thing w/o manifold vacuum is the HVAC system just plug it into the manifold vacuum port on the front driver's side of the carb, as shown in Figure 1 in the Edelbrock installation manual. But, as was said, you do need the check valve/tee and vacuum reservoir shown in the Vacuum Systems pics or your HVAC system will default to Defrost when the vacuum goes away with heavy throttle.

As for the ones on the thermostat housing, they are temperature controlled and were part of a complex system to provide vacuum for various emissions systems at specific temps. Since you have an aftermarket carb and no belt on the AIR pump I'm guessing you aren't worried about emissions. In that case I would remove those valves and plug the holes with pipe fittings. Then I'd set my vacuum advance up with ported vacuum from the timed port on the Edelbrock carb, which is the port on the front passenger's side.

And if you aren't using the thermactor system we can talk about how to remove it.

Gary,

My 460 never had any check valve or reservoir can or bubble.

I think these big engines without cats never had them.

So, really all he needs is manifold vacuum applied to the HVAC selector.

[84-460-Project]

Gary,

My 460 never had any check valve or reservoir can or bubble.

I think these big engines without cats never had them.

So, really all he needs is manifold vacuum applied to the HVAC selector.

Any chance I could get you to take a picture of your vacuum set up?

 

[ArdWrknTrk]

Any chance I could get you to take a picture of your vacuum set up?

Sure. But it's pouring rain here in CT right now.

My truck has been desmogged, but my vacuum sticker is on display in Gary's archives, along with Bill's '86.

They are the same for all intents and purposes.

[Gary Lewis]

I'll try the the manifold vacuum to HVAC. Have you tried this work around with success?

So ported vacuum (vacuum at idle) is vacuum all the time and manifold vacuum (timed vacuum) is only when the engine is accelerating?

I've not put the HVAC hose to the carb, but it will work. The manifold vacuum off the manifold is the same as the manifold vacuum port on the carb. In fact, if you pull the carb and trace that port you'll see it makes a 90 and goes down into the manifold.

But, you have ported/timed and manifold vacuum backwards. Manifold vacuum is there all the time, but timed or ported vacuum is not there at idle and comes in as you open the throttle slightly. I like timed vacuum for the vacuum advance.

The vacuum diagrams Jim referred to are here: Documentation/Underhood/Vacuum Systems/Vacuum Diagrams/460 V8.

Jim - The EVTM doesn't differentiate by engine. The vacuum diagram is shown below, and that's the same setup Big Blue has. Perhaps the '87 and later ones have the vacuum tank and check valve built into the system in the cab?

[85lebaront2]

Any chance I could get you to take a picture of your vacuum set up?

Here is mine for emissions:

On mine, white is the EGR valve ported vacuum signal

Green is the EGR valve signal from the 4 port thermal vacuum valve on the thermostat housing

It also goes to two of the four purge control valves and is run through a delay valve

Yellow is a ported signal for one of the purge valves

Red is direct manifold vacuum and goes to the vacuum bowl vent valves, the air filter heat control and WOT air inlet, one purge valve, the two air pump diverter valves and the bottom port on the 4 port valve, through a restrictor to the upper port on the 3 port thermal vacuum valve.

Black is from the 2nd port on the 4 port valve, and there is a big (3/8") hode to a front manifold port for the purge system. the smaller black lines run to the air pump diverter valves through a vacuum control valve.

Here is what the vacuum harness looked like off the engine, repaired section in the middle of the bundle is where the exhaust crossover melted it.

[Gary Lewis]

Here is mine for emissions:

On mine, white is the EGR valve ported vacuum signal

Green is the EGR valve signal from the 4 port thermal vacuum valve on the thermostat housing

It also goes to two of the four purge control valves and is run through a delay valve

Yellow is a ported signal for one of the purge valves

Red is direct manifold vacuum and goes to the vacuum bowl vent valves, the air filter heat control and WOT air inlet, one purge valve, the two air pump diverter valves and the bottom port on the 4 port valve, through a restrictor to the upper port on the 3 port thermal vacuum valve.

Black is from the 2nd port on the 4 port valve, and there is a big (3/8") hode to a front manifold port for the purge system. the smaller black lines run to the air pump diverter valves through a vacuum control valve.

Here is what the vacuum harness looked like off the engine, repaired section in the middle of the bundle is where the exhaust crossover melted it.

Bill - Does Darth have the vacuum reservoir for HVAC and the check valve?

[85lebaront2]

Bill - Does Darth have the vacuum reservoir for HVAC and the check valve?

Now he does, I believe he had a metal one originally, looked like a large soup can on the right inner fender. Since replaced by the plastic one on the side of the evaporator housing. I went through my emission labels, there were only 3 systems in 1984 and two of them match what his looks like. I reduced them both to forum size and can post them or you should have them 3-97J-R10 and 3-97J-R11, the other one 4-98S-R0 is much more complex and may have been late 84 or CA spec 84. Since his has a Carter rather than Holley carb, it can probably be used as it doesn't seem to have the bowl vent valves.

Here, these two may help, these are 1983-84 460 diagrams:

These show the components on the engine.

[Gary Lewis]

Now he does, I believe he had a metal one originally, looked like a large soup can on the right inner fender. Since replaced by the plastic one on the side of the evaporator housing. I went through my emission labels, there were only 3 systems in 1984 and two of them match what his looks like. I reduced them both to forum size and can post them or you should have them 3-97J-R10 and 3-97J-R11, the other one 4-98S-R0 is much more complex and may have been late 84 or CA spec 84. Since his has a Carter rather than Holley carb, it can probably be used as it doesn't seem to have the bowl vent valves.

Here, these two may help, these are 1983-84 460 diagrams:

These show the components on the engine.

Jim said his doesn't have the reservoir nor the check valve, so I wonder if that is an '87 and later thing.

On the diagrams, I think I have a book of diagrams that I've not scanned in, so if you have those post them, please.

That's another area we could flesh out. We have some diagrams, but not all.

[ArdWrknTrk]

Jim - The EVTM doesn't differentiate by engine. The vacuum diagram is shown below, and that's the same setup Big Blue has. Perhaps the '87 and later ones have the vacuum tank and check valve built into the system in the cab?

http://forum.garysgaragemahal.com/file/n44349/7637760_orig.jpg

No Gary.

My truck definitely never had any vacuum reservoir or check valve.

I will take pics of what is left in the AM when the rain stops.