Trans Am Information > DriveTrain
Vacuum lines
ta78w72:
I'm very confused. I'm missing the ported vacuum switch (TVS) on my 1978 4-speed 400. The service manual says "V8 400 engines with manual transmission use ported vacuum for distributor spark with a coolant overheat TVS which provides full manifold vacuum to the distributor when the engine coolant temperature is above apporximately 225 degrees F."
The schematic, figures 6E-27, 28 and 29 show a TVV for manual and a TVS for automatic. This is exactly opposite of the text. Which is correct for a 4-speed? I assume the schematic is incorrect.
Does anyone have a picture of where this vacuum switch is located? I need to get the vacuum hooked up according to the schematic on the radiator bracket in order to pass the California smog test.
Black78TA:
--- Quote from: "ta78w72" ---I'm very confused. I'm missing the ported vacuum switch (TVS) on my 1978 4-speed 400. The service manual says "V8 400 engines with manual transmission use ported vacuum for distributor spark with a coolant overheat TVS which provides full manifold vacuum to the distributor when the engine coolant temperature is above apporximately 225 degrees F."
The schematic, figures 6E-27, 28 and 29 show a TVV for manual and a TVS for automatic. This is exactly opposite of the text. Which is correct for a 4-speed? I assume the schematic is incorrect.
Does anyone have a picture of where this vacuum switch is located? I need to get the vacuum hooked up according to the schematic on the radiator bracket in order to pass the California smog test.
--- End quote ---
I think I might be able to help.I also have a 78 W72 4-speed. :) I still have all the emission controls intact. Schematic 6E-27 is correct for your car. Forget about the other diagrams, they are not correct for your car anyway.
The TVS is located on the air cleaner. The pic is big to show detail. There are also two TVV "posts". One is on the intake manifold,the other is near the exhaust manifold on the right side. If you need some more detailed pics let me know.[img][/img]
ta78w72:
Hmmmm, Thanks for posting the picture. But I think your picture shows the sub TVS. I found where the DS-TVS is located, in the head between cyclinder number 6 and 8. I think the schematic incorrectly lists it as a DS-TVV. Mine was not hooked up. I got lucky with the smog test last time.
Black78TA:
--- Quote from: "ta78w72" ---Hmmmm, Thanks for posting the picture. But I think your picture shows the sub TVS. I found where the DS-TVS is located, in the head between cyclinder number 6 and 8. I think the schematic incorrectly lists it as a DS-TVV. Mine was not hooked up. I got lucky with the smog test last time.
--- End quote ---
I have the same drivetrain as you and can provide any pic that will help you make your car factory correct. Ask and you shall receive.
ta78w72:
Thanks for the offer, I appreciate it. I've taken out all the non factory stuff. The next project is replaciing my heater core....then it's on to replacing the manual roll up windows with power windows, new glass and power door locks.
I get the car back from the shop tommorw. It's getting the transmission rebuilt. Someone also did some welding on the hurst linkage. That's getting fixed too. When it comes to transmissions, I let someone who knows what they're doing handle it. All those gears, clips and needle bearings give me chills! Also, a new clutch, pressure plate and flywheel. I'll be ready to go for summer!
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