1972 LT-1 Spark Control Solenoid.

[STEVE MUELLER]

Dear Sirs:

I have a question:

1. On my 72 LT-1 I know that the vaccum advance goes from the distributo to the advance to the spark control solenoid out to a T which then goes to a carb solenoid then to another part of the car and then to the Air pump. On My car the vaccum was running unattached to any of these items. I have all of the components but the harness.

2. Where can I get a harness and the part # 3. Where does the harness connect on the car, there is two open electrical plugs one near the distributor and another near the heater box. 4. Lastly how does the whole system work???????

steve

[Bill Nichols]

Re: 1972 LT-1 Spark Control Solenoid.

I cannot remember the wire routing, but I can explain the system operation. The pupose of the solenoid is to interupt the vacuum from the carburetor to the vacuum advance at the distributor. There are two control features. One is temperature , based on the coolant temperature sensor, and the other is a switch at the transmission that is used to determine which gear the car is in. Basically, the spark advance is interupted in 1st, 2nd, and 3rd gear once the engine is warmed up. The purpose of this was to reduce the emissions in those gears. Functionally, connecting the carburetor port directly to the vacuum advance is fine. However, if you want it to respond as it did new, then you need to correctly connect the solenoid.

[STEVE MUELLER]

Re: 1972 LT-1 Spark Control Solenoid.

Bill:

Do you know where I can get the onformation on the wiring ports and parts #s

steve

[Joe L.]

Re: 1972 LT-1 Spark Control Solenoid.

Steve----

I think that you will find all of the information that you seek in the 1972 AIM. This and the 1972 Chevrolet Service Manual are ABSOLUTELY essential if you are going to work on your own car.

Bear in mind, though, that most of the part numbers shown in the AIM will be discontinued by now. This is especially true for the components of this TCS emissions system. The only part of this system which I believe is still available is the transmission-mounted switch.The electrical harnesses are ALL GM-discontinued but usually available from Lectric Limited or M&H Electrical Fabricators.

[Patrick H.]

Re: 1972 LT-1 Spark Control Solenoid.

Steve,

In addition, most of the other components are available through Sal Carbone of RPO Vette, at rpovette@aol.com

He tends to specialize in these items.

Patrick

[Duke W.]

Re: 1972 LT-1 Spark Control Solenoid.

Obviously you want all the TCS hardware in place and working, but I would recommend porting the vacuum can directly to the manifold (like they did in the good old pre-emission days) for normal driving. The conversion back and forth should be easy. Also, you could change the vacuum can and centrifugal advance to better settings for performance and economy. The late '64 and '65 FI distributors were the best setup the factory every did. Max centrifugal advance was all in by 2350, and this should work out okay on your LT-1 if your don't raise the CR. Your ignition is set up for emissions, not performance and fuel economy, which generally have the same requirements.

Duke

[Jim T.]

Re: 1972 LT-1 Spark Control Solenoid.

Duke I agree with you on having the vacuum advance hooked directly to engine vacuum. One of the first things I did to my 70 Corvette when I bought it new was bypass the TCS system. Gas mileage went up with city driving. Never have changed it. I used a full time vacuum port from the the carburator.

[Jack H.]

In addition....

I don't believe original solenoids were actually built by GM/Delco. My gut tells me if you pull the drawings you'll find these were purchased parts mfgr'd by independent 3rd parties who put DR marks on as an OEM courtesy.

I'll bet umpteen big brown round ones, you can go to your independent parts dealer and find the functional equivalent (perhaps sans the DR P/N and/or date code) sitting new in box at your local warehouse distributor for SUPER cheap money....

Also, I'll up the bet that these were 'Corvette only' items and take a flying leap of faith they were across-the-board Chevy car/truck use items that you can find at you local scrap yard for $1-2 each and if you want to rev up your home plating tank you can have a correct/correct dated NOS original in a matter of minutes....

Last, if these 'tricks' are beyond the individual's experience sphere, you simply pick up the current Paragon catalog and order a restored original (where someone else did the above bush shaking for a profit)....

[Terry M.]

Re: In addition....

TIP: All the vacuum solenoids can & electrical components were the same for, I believe, all, or most GM in a given year and system. The difference is in the mounting bracket, which is the part with the number & DR stamped on it.

Bracket can easily be changed from functioning to non functioning part. Thus Jacks favored trip to automotive recycler can yield you many solenoids off of other same model year GM vehicles. Hy ye to the recycling depot.

Terry