Vacuum / Emissions Question

[willem445]

Hey guys, I think I have most of the vacuum / emissions on my 350 figured out but I'm not sure what these two pieces are. Anybody have any ideas? They are T'ed into the vacuum advance circuit.

[Dead Parrot]

#1 is the normal spot for the idle increase solenoid for AC equipped vehicles. Normally electric. #2 may be where the AC power connects to switch the vacuum on when the AC comp kicks on.

If it never had AC, then it may adjust idle speed when 'something' happens. No clue what that something might be.

[willem445]

Originally Posted by Dead Parrot

#1 is the normal spot for the idle increase solenoid for AC equipped vehicles. Normally electric. #2 may be where the AC power connects to switch the vacuum on when the AC comp kicks on.

If it never had AC, then it may adjust idle speed when 'something' happens. No clue what that something might be.

Thanks for the reply. I think I'll try experimenting with deleting those two elements and see what happens. This truck for sure never had AC. My Dad did mention they parked this truck because of "idle issue". I wonder if it's related to that.

[geezer#99]

#2 is the tcs solenoid.
Translates to transmission controlled spark.
Function is to provide vacuum to the vacuum pot on the distributor only when in high gear.
There should be a ground switch on your transmission.

[geezer#99]

What transmission do you have?

[willem445]

I thought I understood what was going on with my diagram more than I did, I'm still a little confused. Hoping for some clarification.

It's apparent to me that someone modified the vacuum / emissions stuff on this truck. Below is the current state of the vacuum lines:


Here is a picture of my engine with things labeled:


Here are a couple diagrams I found online (unfortunately my truck did not have a diagram anywhere)







From what I can tell, there is no EGR valve or EFE valve. I don't see an EGR block of plate so I feel like this truck didn't have one. So I'm not sure if those two TVS's are actually EFE & EGR but I labeled them as such anyways.

I'm planning on replacing the stock air cleaner with an open air cleaner, thus removing all of the air cleaner related vacuum. This is what I had in mind after deleting things:



Couple questions based on that:

1. It's unclear based on the diagram I can find whether the vacuum advance port from the carb should go through a delay valve & EGR to the distributor, or if if should go directly from carb to distributor. Is going directly to distributor fine?
2. Based on my modified schematic, is the EGR TVS doing anything? It seems since it's not connected to anything that actually supplies vacuum, it's just doing nothing. Is that right? Should I delete that circuit completely? What would the rear choke diaphragm connect to?
3. I'm planning on deleting the EFE TVS circuit altogether. See any problems with that?

[willem445]

Originally Posted by geezer#99

#2 is the tcs solenoid.
Translates to transmission controlled spark.
Function is to provide vacuum to the vacuum pot on the distributor only when in high gear.
There should be a ground switch on your transmission.

Upon googling, you appear to be correct. This eBay listing is nearly identical to what I have. https://www.ebay.com/p/21004643104

Transmission is SM465 manual. Truck has always been manual as far as I can tell. (ie. manual hump in cab, manual steering column, etc.)

[geezer#99]

Likely someone used the tcs to reroute the vac lines.
Maybe your truck never used one. It was just handy for them to use.

Rear vac pot on carb plugs into manifold vacuum port on baseplate on back of carb.

No problem running vac from carb directly to distributor.

[geezer#99]

Do you need to pass a visual emissions test where you live?

[willem445]

Updated my current diagram to be more accurate.

[willem445]

Originally Posted by geezer#99

Likely someone used the tcs to reroute the vac lines.
Maybe your truck never used one. It was just handy for them to use.

Rear vac pot on carb plugs into manifold vacuum port on baseplate on back of carb.

No problem running vac from carb directly to distributor.

No visual or emissions testing of any kind where I live.

When you say "Rear vac pot on carb plugs into manifold vacuum port on baseplate on back of carb", do you mean that the 'secondary pull off diaphragm' would connect directly to the 'Air Cleaner Sensor Full Manifold Vacuum' on the carb (instead of routing through the air cleaner like with stock air cleaner)?

[willem445]

If I'm understanding correct, I think this is what I would end up with for a simplified diagram. Spot any issues?

[geezer#99]

It should be plugged in right there.
A short hose.
The vac pot controls the secondary air door.

[geezer#99]

What you call a ‘vent’ on the valve cover is actually an air inlet.

[willem445]

Originally Posted by geezer#99

What you call a ‘vent’ on the valve cover is actually an air inlet.

Oh you are right! I bought a K&N filter to install in the valve cover intake. It's the other side, the PCV valve, that is the "vent". Thanks! I'll update that on my diagram.

[willem445]

Thank you both! I'm waiting for some parts still and truck is in pieces for rust repair but i'll post an update when I test the simplified routing.

In the meantime, I will monitor this thread for any other inputs or suggestions!