1974 TCS Configuration

[Patrick H.]

Re: 1974 TCS Configuration

Why fool about, just replace it.

Because it's restoration?

And up until about 2 years ago it's the only option that was available?

[Terry M.]

Re: 1974 TCS Configuration

Terry,

What did the third port connect to?

For 1970 applications the port on the end with the electrical connections connects via a hose to the carburetor air inlet horn. For 1971 and 1972 that same port has a cube of foam over it, as Patrick mentions. That port is a vent for the vacuum line to the distributor actuator -- it is not only necessary to stop the vacuum to the actuator, but to vent the actuator to the atmosphere so that it returns to the "rest" or natural position.

[Harmon C.]

Re: 1974 TCS Configuration

My 1970 has three ports, as do most of the TCS solenoids I am familiar with -- which are those up to 1972. In fact this is the first one I have seen with two ports. Maybe the two port is a "newer" feature.

Terry
In the picture of the torn apart solenoid the third port is out of the housing and in the lower right of the picture.

[Terry M.]

Re: 1974 TCS Configuration

Terry
In the picture of the torn apart solenoid the third port is out of the housing and in the lower right of the picture.

I see it now Lyle. So does that mean that even 1974 had the third port? If true that would make me think that perhaps all of the TCS solenoids had three ports.

[Harmon C.]

Re: 1974 TCS Configuration

I think all TCS solenoids had three ports. The only difference I have seen in any of them was the bracket. At one time I bought some NOS solenoids that had an odd bracket for $1.00. I used all the new parts and my original bracket and they work as they should.

[Stuart F.]

Re: 1974 TCS Configuration

Every one of these I've ever seen uses that third port as a vent, as others have mentioned. The vent had a small foam filter, but these seldom lasted too many years. On a 72 I once had, I cemented an old paper fuel filter to the hose. I still have that laying around some place because I liked to use the solenoid with manual switch control to get past the smog Police rather than have the control system determine when I can have full time Vacuum advance. You might want to consider that as an option.

Stu Fox

[Patrick H.]

Re: 1974 TCS Configuration

You have to assume they know what they are looking at. Not funny Mike.

I would assume that they don't. Even the odds of the NCRS guy judging your car knowing how it is really supposed to appear is quite small. I have seen top level judges totally oblivious to mis-routed and connected TCS systems. You really think the smog guys in Ontario know how it's supposed to be routed?

Far more likely is that they look in "some book" that has it all incorrect and you have to spend your time convincing them of how it's really supposed to be configured.

Patrick

[Paul L.]

Re: 1974 TCS Configuration

Every one of these I've ever seen uses that third port as a vent, as others have mentioned. The vent had a small foam filter, but these seldom lasted too many years. On a 72 I once had, I cemented an old paper fuel filter to the hose. I still have that laying around some place because I liked to use the solenoid with manual switch control to get past the smog Police rather than have the control system determine when I can have full time Vacuum advance. You might want to consider that as an option.

Stu Fox

Stu,
What do you mean by "manual switch control"?

[Stuart F.]

Re: 1974 TCS Configuration

The solenoid is picked up by a 12v signal applied to it from the emission control system, i.e. typically something like 7 seconds after your tranny goes into high gear for cruising. Therefore you provide it with a manually switched 12v source (hidden of course) so you can control when it is picked up to give you vacuum advance. The vacuum source (port) in the carb may then be opened up if you want full time manifold vacuum. In the QJ, that port connects to a chamber at the butterfly with it's port slightly above the butterfly. A simple drill or file procedure can be used to open the port into the chamber so it is at or below the butterfly position at idle.

Stu Fox

[Terry M.]

Re: 1974 TCS Configuration

I think all TCS solenoids had three ports. The only difference I have seen in any of them was the bracket. At one time I bought some NOS solenoids that had an odd bracket for $1.00. I used all the new parts and my original bracket and they work as they should.

Lyle, I have believed for years that the solenoid was the same for all of them -- but I never tried to "restore" them like you did. I know several other folks who have done that successfully, though.

My original belief about all the solenoids being the same has been reinforced by your statements. I'll just ignore the two-port v three port nonsense.

[Paul L.]

Re: 1974 TCS Configuration

Thanks Stu.

[Michael W.]

Re: 1974 TCS Configuration

Terry,

It might seem 'nonsense' to you, but not all of us have the years of exposure you have had and are still learning. I know I'm very much still in the latter category.

Here are some photos of a NOS 1997410 solenoid which is common to '73 and '74 L48 4 speed cars, and possibly other applications. This is the peice that I have referred to as a two port solenoid, for obvious reasons. It is hardly obvious by casual observation that this is actually a three port solenoid especially when clues offered by other members mention that the third port would have a rubber tube and foam filter attached. It is also markedly different than Paul's solenoid, and more than by simple placement of the mounting bracket. The vent (or third port) becomes partially visible in the third picture and can really only be seen in the fourth picture when backlit through the screen/filter.

It could be that this particular solenoid is a service replacement part and different in configuration than assembly line pieces. If so, then this knowledge might be useful to other restorers or on the judging field.

[Paul L.]

Re: 1974 TCS Configuration

Terry,

It might seem 'nonsense' to you, but not all of us have the years of exposure you have had and are still learning. I know I'm very much still in the latter category.

Here are some photos of a NOS 1997410 solenoid which is common to '73 and '74 L48 4 speed cars, and possibly other applications. This is the peice that I have referred to as a two port solenoid, for obvious reasons. It is hardly obvious by casual observation that this is actually a three port solenoid especially when clues offered by other members mention that the third port would have a rubber tube and foam filter attached. It is also markedly different than Paul's solenoid, and more than by simple placement of the mounting bracket. The vent (or third port) becomes partially visible in the third picture and can really only be seen in the fourth picture when backlit through the screen/filter.

It could be that this particular solenoid is a service replacement part and different in configuration than assembly line pieces. If so, then this knowledge might be useful to other restorers or on the judging field.

Yes Mike,

The 1997410 is obviously different from the 1997425 that I have. And Dr. Rebuild says that that is the difference between the four-speed and the TH400. Yes the ...425 is definitely three-port. It came from that PartsLadi in Florida.

[Harmon C.]

Re: 1974 TCS Configuration

Terry,

It might seem 'nonsense' to you, but not all of us have the years of exposure you have had and are still learning. I know I'm very much still in the latter category.

Here are some photos of a NOS 1997410 solenoid which is common to '73 and '74 L48 4 speed cars, and possibly other applications. This is the peice that I have referred to as a two port solenoid, for obvious reasons. It is hardly obvious by casual observation that this is actually a three port solenoid especially when clues offered by other members mention that the third port would have a rubber tube and foam filter attached. It is also markedly different than Paul's solenoid, and more than by simple placement of the mounting bracket. The vent (or third port) becomes partially visible in the third picture and can really only be seen in the fourth picture when backlit through the screen/filter.

It could be that this particular solenoid is a service replacement part and different in configuration than assembly line pieces. If so, then this knowledge might be useful to other restorers or on the judging field.

I think it is a service replacement as I have seen many 7410's With just the tube on the rear. The filter may just be pushed on the tube.

[Michael W.]

Re: 1974 TCS Configuration

Here's another version, note the white connector

http://cgi.ebay.com/ebaymotors/73-4-Chevrolet-&-corvette-nos-tcs-solenoid_W0QQitemZ380208725741QQcmdZViewItemQQimsxZ20100228?IMSfp=TL1002281310007r10960