Topic: vacuum routing 1979 w-72

[drtracer58]

I recently bought a 79 T/A that someone had removed or rearranged all the vacuum lines, I have a Schematic , but my question is... The hose/line from the TVS on the front of the Intake to the driver side exhaust manifold, Is it rubber all the way or metal tube with a rubber hose on each end   I can't seem to find any pictures of it anywhere  I don't know the terminology for all the items        EFE Valve =??       SVB-TVS= ??  where is it located ?   
DS-VMV = ??  Where is it located        I have figured out that TVS= Thermal Vacuum switch " I Think"      also can't find what is the correct size of hose , I do know some are bigger than others       

[Burd Turd]

Just happen to have a shot of the EFE, it's on the drivers side between the exhaust and the manifold  Early fuel evaporation, i think. Its the only metal line on that system, at least for 1978

[4SPEED]

[drtracer58]

Thanks Burd & 4-Speed,   That is the drawing I am using from the CD I bought from Brett, It helps but I still am not sure where the location is at on some of the parts,I am betting it is the ones located in the shaker base !!!    Anybody have one of the tubes for sale or know where I might find one ??

 BURD,  I am finally getting around to installing the TVS I got from you   Thanks Again ...

[Burd Turd]

There is 2 diff dia's for the 400 in my GM book, one for dual exhaust, and one for single.and a high alt too. 3 actually.What car would be the single exhaust, my car had the muffler w/3 holes in it, is that considered duals? They had duals from the cat back too
Glad to help on the TVS!

[4SPEED]

to your question,  No.  the metal line runs from the efe valve, with a maybe 3" high heat tube .  the metal line runs to the right side of the intake then a rubber vack line the rest of the way to the switch.

the pic I posted is correct. in 79 there was only one 400, the W72 4 speed

the last dual exhaust was in, what?  73 I think. not sure.   
and the high altitude , thats a carb change. and I only know of the 1 carb for the 79 w72.

but I've been wrong before...

[drtracer58]

Heat Tube     I am not sure I understand ...   Maybe I should have been asking for a metal line , not a tube ?.   But Am I correct in thinking it only comes over near the distributor ,then goes rubber the rest of the way ?

[Burd Turd]

The metal tube you can see in my photo is longer than 3", it has a high heat rubber pc. that goes on the efe, it gets hot down there,sounds like we are confusing you more than helping. The ds-tvs is in the side of the air cleaner, in the air cleaner base is a heat modulator, and the light blue snorkle door sensor, I have all those if you need one.

[Burd Turd]

Look at this, heres the choke modulator, and the dual exhaust for 78-79, and the vac routing for the dual exhaust and the single like what i have, 79 I thought used the 78 gm manual also, in that case there were two types of exhaust on the z engines,

[drtracer58]

I think all I am missing is the metal line and the clip that attaches it to the exhaust manifold     Thanks for the pictures , they help with visuals , I feel confident I can find the line, If not I guess I will have to fab one if I can find a picture of a complete one .. 

[drtracer58]

Can anybody tell me what  DS-VMV is ??   and where it is located

[ta78w72]

Can anybody tell me what  DS-VMV is ??   and where it is located

It's interesting.  The 1979 W72 engines are just the 1978 engines saved for 1979, yet they have different emission diagrams.  The 78 manual doesn't show a DS-VMV.  If it were my car, I'd use the 78 manual and the diagram for the 78 Z four speed.  They got a little crazy with the vacuum lines in 79.  

They may have changed some nomenclature from 78 to 79 also.  They use TVS (thermal vacuum switch) in 78 and TVV (which I assume means thermal vacuum valve) in 79.  I assume those are really the same parts.

The DS-VMV (distributor spark vacuum modulator valve) would be a vacuum modulator valve that would be connected by vacuum lines to the distributor as shown on the above diagram.  It floats with the vacuum lines and is not something that bolts somewhere.

My 78 doesn't use a DS-VMV so I couldn't tell you where to find one.....but I can't believe you couldn't simply use the 78 configuration which omits that part.

[ta78w72]

to your question,  No.  the metal line runs from the efe valve, with a maybe 3" high heat tube .  the metal line runs to the right side of the intake then a rubber vack line the rest of the way to the switch.

the pic I posted is correct. in 79 there was only one 400, the W72 4 speed

the last dual exhaust was in, what?  73 I think. not sure.   
and the high altitude , thats a carb change. and I only know of the 1 carb for the 79 w72.

but I've been wrong before...

You're kind of correct and kind of wrong.  They aren't true dual exhaust as the exhaust is routed through one line to the cat and then out the cat to two mufflers.  So, they kind of had dual exhaust and kind of didn't.  But basically, you're right, no true dual exhaust.

I think the non W72 400's had one muffler.  Some had one exit (single exhaust) and some had two exits (dual exhaust).  Not true dual exhaust that for sure.  I think they wanted to save money on cats.  Why put two cats in a car wihen you can get by with one.

[Burd Turd]

My 78 L78 400 had the 3 hole muffler, what a bad system, I have the cat and the crossover saved, why I don't know.I had my carb rebuilt the first time around 1984, the ds-vmv was removed by the carb guy when he set up my carb, I don't have one on now, and I think the charcoal canister is all thats hooked up.

[drtracer58]

Now I am really confused     Quote from 79 manual : The DS-VMV limits the distibutor spark vacuum to a calibrated value until ported vacuum applied to the control port of the DS-VMV is greater than the calibration value        THAT SURE WENT OVER MY HEAD ......