Hi guys,

It's been a while since I’ve posted here but every time I run into a problem this board always helps me.

My car is a 1985 Z28 non-computer controlled (Canadian model). Are all TVS the same or are they different. I’m asking this because I need to buy a new one. The one I need is located on the water neck. The ported vacuum line run from the carb to the TVS then go to the distributor (in between somewhere there is a delay valve). Now my problem is that the existing TVS that was on the water neck that I accidentally broke has markings on it stating that one of the port should go to the carb and the other one to the EGR. Now I know this is wrong because the TVS with the vacuum line that goes to the EGR is located on the intake manifold itself. Does all this make sense? Can somebody help me out here?

Thanks

 

I don't know if this is of any help but here is the emission hose routing...

 

They're usually different. Your dealer parts counter should be able to figure out which one you need, if it's still available.

 

Thanks to Vader for this!

Matches my non CC 85 Z28 perfectly.


All the TVS's are not the same. The EFE TVS lets vac thru only when the engine is cold. EGR when hot ect.

 

Ok here’s the deal. I went to three different auto parts store and called three different GM dealers and I’m out of luck. The part stores need the original valve to cross reference it with the one they have in their books so I called GM. According to them, their book says there is no TVS valve on the water neck except for the EFE and a coolant sensor. I’m not stupid there is two TVS in my water neck and the emission hose routing shows that I should have a total of three TVS’s. Can anybody with the same setup as me go and check there car and tell me the part numbers of those three TVS? The one I need the most is the one on the passenger side on the water neck that connect to the distributor. For now I just routed the hose directly from the carb to the distributor is this fine? Should I just leave it like that and don’t bother getting another one?

Thanks

 

The purpose of the TVS is purely for emissions reduction. There aren't any performance, economy, or longevity issues involved in not having it.

 

Just as there are no issues involved with keeping it, if everything is still in working order and you don't have emissions issues to worry about. As soon as something fails though the whole system can go.

 

So you’re saying that I shouldn’t bother getting a new one and just leave it connected directly from the carb to the distributor? Doesn’t it affect the timing somehow since it’s keeping vacuum from going to the distributor before a certain temperature?

 

Vacuum advance distributors had vacuum from the first second of running until the late 70's. How many issues came up because of having vacuum immediately for all those years, do you think?

The non-CC systems are pretty simple. This was a band-aid for one short period of operation that was less expensive than a full CC setup. Emissions will be slightly higher while cold, but it will never cause a sniffer failure because the car is fully warmed when you go in for an emissions test. It might be failed on a visual inspection, though.

 

Ben85Z28 can you take a pic of your water neck and the routing? I have a 84 berlinetta and mine has the TVC on the right side of the water neck and a coolant temp sensor on the left side. My TVS broke and i have no idea how to toute the hoses or if there is a way to bypass the swuitch

 

I have a 1984 Trans AM 305 ci. I have remove both tvs on the thermostat housing & screwed in nft pipe plugs. I have eliminated the butterfly in the heat riser, removed & capped the egr valve. As stated above, u do not need any of these tvs switches. I have tvs #9006 available. It connects to the smaller hole port on the thermostat housing.
The is tvs remaining is at the rear of the intake manifold & there is no way to remove it as it supplies vacuum to two other units.
There is another tvs that u can see in the pictures with two nail heads plugging the ports. This unit will be removed when I remove the intake manifold to repaint.
I am including pictures of the routing with no TVS.