[Treeguy68]

I have a 1986 Chevy 350 with a 1406 Edelbrock carburetor The transmission is a turbo 350. My question is on the transmission is there another vacuum line other than the vacuum Modulator. Also what would cause the truck to stall out as I put it into gear but it idles fine when in park or neutral?

 

[cobalt327]

I have a 1986 Chevy 350 with a 1406 Edelbrock carburetor The transmission is a turbo 350. My question is on the transmission is there another vacuum line other than the vacuum Modulator. Also what would cause the truck to stall out as I put it into gear but it idles fine when in park or neutral?

There is just one vacuum line, it goes to the modulator.

If the tranny is original to that truck it has a lock up torque converter (TH350C). If the solenoid or wiring is bad the TC can stay locked up causing the engine to stall.

You can temporarily disconnect the lock up to drive it w/o lock up until you get it fixed. Just unplug the terminal on the left side of the tranny to see if that's the problem.

 

[Treeguy68]

If I advance the idle it runs choppy at idle in gear but I can give it gas and it drives and shifts fine

 

[gearheadslife]

it's a truck the 2nd vac line might be going to the vent tube.. we did this to trucks we use to launch boats so water didn't get in the trans.. just a thought

 

[cobalt327]

When's the last time it was tuned up? Is the vacuum advance working and the timing set right?

Choke fully opening?

Vacuum leaks?

 

[Treeguy68]

It's a brand new carb and I never hooked up the vaccum advance. Not sure which port to go to on the carb. Left or right port of the pcv port?

 

[cobalt327]

Try the driver side vacuum port first, that's the manifold vacuum port. I would expect the idle speed to increase when you hook it up so you might need to lower the curb idle using the adjustment screw to turn the idle speed back down if needed.

 

[Treeguy68]

I don't see any wires hooked to the tanny

 

[cobalt327]

I don't see any wires hooked to the tanny

Then the problem isn't the torque converter lock up, at least.

Try hooking up the vacuum advance like I said above. If the idle speed doesn't increade the vacuum advance unit is prob. bad.

 

[Treeguy68]

When I hook it up the motor just dies out

 

[charlie chop top]

Helping hand

I think you have a serious vacuum problem.

 

[Treeguy68]

With the vacuum modulator on the transmission have something to do with it?

 

[streetrodderbn]

I have seen the modulator valve go bad, You usually can pull the rubber line off and see tranny fluid leaking from the vacuum port coming from the modulator, But....it sounds like a vacuum leak at the carb if it ran fine until you replaced the carb though. what intake is on the engine? a Quadrajet intake will require at least the steel adapter plate on a spreadbore intake to prevent a serious vacuum leak.

 

[cobalt327]

When I hook it up the motor just dies out

That could mean that the added timing is just too much for the engine to remain running. Or it could even mean the leads from the pick up coil to the ignition module have broken inside the insulation and the flexing is causing a break in the circuit.

Is this an HEI distributor? Have you got a timing light that you can use?