70 LT-1 Vacuum Advance Solenoid

[Hotrodpaul]

I am having trouble with the idle on my 70 Z Auto. I have set the idle at 900 RPM but when I shift into drive or reverse the idle speed reduces to 500 or so and the engine wants to die. I have listed some pics of the solenoid which works and is energized when the ignition is on.

It seems to me that the solenoid should be energized in reverse or drive to add vacuum advance to the distributor, raising the idle speed in gear. Here are a few pics of the solenoid:



http://i3.photobucket.com/albums/y86...6/DSCN0228.jpg

Anyone have a pic of the correct hose routing? Thanks,

Paul

[70Z]

This help?

[Hotrodpaul]

I can't tell where the hoses terminale. I assume the left one goes to the vacuum advance, the middle one to the carb vent and the right to manifold vacuum? What is the function of this solenoid?

Paul

[Belair62]

You are correct in their location except the right hose goes to the carb vacuum port Paul...this solenoid activates and sends vacuum to the distributor in 3rd and 4th gear on a 4 sped...not sure on auto ....it's called a TCS solenoid...it was an emission thing I believe.

[Jacsey 70Z]

I'm not sure that's the type solenoid you should have for a auto car. Yours should be on the Carb. It's a combination TCS CCS it has the hose that goes to the vacuum advance. On the auto cars you get vacuum in reverse and 3rd.
I've never owned a automatic car just read about the system when I was trying to get my TCS working on my 4 speed car.
Jack

[Belair62]

Paul...I learned the vac line routing over at NastyZ28.com where Jack posted pics for everyone...you may want to stop over there and ask around unless someone around here can dig up the automatic version...

[Mr70]

The transmission type didn't dictate the TCS unit used.
In 1970,it was it's own seperate unit.
All Small Blocks used the same design,part#1114432,as did the Big Blocks,part#1114434.The Mounting brackets were the difference in the part #'s.

New for 1971,the TCS solenoid was reconfigured into the Idle speed solenoid.This was incredibly heat prone,more so then the earlier design,and very unrealiable.

In 1972,the TCS solenoid became it's own seperate part again.

[Hotrodpaul]

Mine is PN DR1114432. I tested the solenoid and without power the metal vacuum tube (one on the right) and the plastic tube (pointing out at 90 gegrees) are connected. With power applied, the metal tube is blocked and both plastic tubes are then connected.

That means if the engine vacuum is applied in the above fashion, it would never reach the distributor. Is this solenoid supplying vacuum to the distributor when energized or with no voltage? The assembly manual shows one leg of the solenoid wiring going to the "TRANS SW. CONN" Which switch is this? Is it on the trans? The other leg goes through the "TCS RELAY" What is the function of this relay? To isolate another switch from the current draw?

Thanks, Paul

[Hotrodpaul]

Just found the correct hose routing in the Assy manual:

Manifold Vacuum - Metal hose barb to the right
Dist Vacuum Advance - Plastic barb @ 90 degrees to solenoid centerline
Carb Vent - Plastic Hose barb to the left, in line with soleniod axis.

This routing makes sense, based on my previous post. Looks like when the solenoid is energized, vacuum is blocked and engine is running without the additional timing. When voltage is removed, with the car in reverse or drive (majority of the time), vacuum is allowed to pass to the advance canister, adding timing to the engine.

I would assume this is done in reverse and drive to prevent the engine from dying. There is also a temp switch located in the head that must be wired in as well but I do not know its function. A little more research to go.

Paul
69 Camaro SS L78
70 Z28 LT1 M40

[Belair62]

The engine has to be at operating temp for the stuff to work as engineered..temp sender achieves that.