Vacuum Source 1980 Trans Am 4.9 w/ Turbo 350
 

I have a car w/ all the vacuum lines & everything in place as factory. I'd like to remove some & or refurbish the cracking tubing. I have a trans that shifts perfectly. I don't want to mess up my vacuum modulator's source. Where is the line to this. Darned if I can locate it. I have all the factory manuals & proper diagrams. They just don't show the trans line. They are perfect on everything else that I see.

I'm looking for a metal line running to the back of the engine. Can't find anything. It's very hard to see behind it all w/ the many tubes & wires. I've even tried a camera w/ no luck. There has to be a vacuum line. On my 1971 Cutlass 350 it's dead obvious. No luck here.

This is from the 1980 Assembly Manual, do you have it?


https://live.staticflickr.com/65535/...77f7cb96_b.jpgScreenshot (73) by Ben, on Flickr

The metal line for the vac mod should be connected to the carb vac tree right on the top, you can just barely see it in the diagram posted, but what youre looking for is a tight bend in the metal line with a small piece of rubber that connects to the top port on the carb vac tree.

If its missing or damaged you can buy a similar size of brake line or tubing from a auto parts store & bend it to fit... or as a last resort you can use rubber reinforced fuel injection fuel line there that will work temporarily but metal is best.

You can also remove much of the vac lines related to emissions like the charcoal canister, EGR valve (use a block off plate) and also remove or gut the smog pump will free up a little drag on the engine... along with that remove the catalytic converter to free up the exhaust and get some good free flowing mufflers. That is if you dont care about those emission items or dont live in a state that does testing... or if you dont care about originality of the car & want a little better performance.

Glad we could help. No response required.

Yes, thank you for the picture. I've put the search on hold right now until it gets a little warmer. I have the manual but didn't see that page.

On my 1981, the modultor vacuum line connects to a t-fitting on the intake like the 81 assembly manual shows.

What car/engine is that for? My 81 301T trans mod line connects to the vac tree on the carb, just like shown in the 1980 diagram above.

Hi 78, It's a 1981 305 chevy.

Thanks for the info... a 305 chevy apparently is different than the 301 turbo the OP is asking about.

Problem solved. I was "taken" to a degree when I bought this car. It was way too nice for what I paid. Looks perfect & runs great. Everything works. 500 miles driven last summer.

I was checking all the vacuum lines since they were brittle & old. Turns out it has a Turbo 200C trans in the car. That trans has a TV cable & not a Vacuum Modulator. Engine is not a turbo, but a plain 301 from 1980 w/ 4bbl. They didn't originally ever have a 200C in these cars. Direct bolt in. It was rebuilt just before I bought it. Runs & shifts perfectly. I double checked the TV cable. It's good.

If it craps out, I'll have a 350 turbo installed. Hopefully w/ conservative driving it should be OK. It can handle the torque of a plain 301. The TV bracket on the intake looks like it's been there forever. Also, the engine has all the vacuum & electric switching on it for an electric lock up torque converter. Nothing looks disturbed or new. I guess this was switched out long ago in the cars life.

Something I'd never expect to find. Interesting. OK for now, I still have a good deal. Thanks for the advice.

You're welcome. Looks like we are zero for two.

It wasn't even a turbo 301?
Ok I'm a bit lost on that one.
As for the trans, they did use the TH200 behind the 301 in non-Firebird models. It may have had a complete driveline swap, or just the trans. Or was it a Turbo car converted to standard? Was never Turbo? Of course that, and computer swap and for trans is difficult.

Thanks for the information. It's good to hear that a Non Turbo 301 engine won't destroy a 200C trans. Mine has a lock up torque converter. There is no computer in my 1980 car. Trans is shifted by a TV cable. The lockup on this one is controlled by a vacuum signal to an electric switch on top of the engine. Electric wire to a solenoid inside the trans.

Yeah I got confused seeing the title "301 w/turbo"... was early morning so overlooked the 350 part. Also not familiar with the 200c trans.