I have a Chevelle 70ss w396/350hp. There is a round cylinder (currently not being used) mounted on top of the manifold, between the carburetor and the valve cover, on the right side, that I can’t identify. It is approx. 3inch round and 3inchs long with a nipple for a vacuum hose in the front. My first thought was it has something to do with the cowl induction but there is no evidence of extra hoses or empty holes. I would appreciate if someone could tell me 1) what this part is 2) what it is used for & 3) how to hook it up.

Also, this car came stock (on build sheet) with option K05 engine block heater. Can anyone tell me if this is the same block heater GM uses today on big blocks? I haven’t tried it to see if it works or not because I don’t want to take the chance unless I can replace it. It would be nice to use this in the winter since my shop is not heated.

Thanks in advance

David,
I have a 70 with a 307 and I have this same little cannister. It was used to run a vacuum line up to the snorkel on the air cleaner. My cannister has two vacuum fittings on the end towards the firewall (in an L shape) and one vacuum fitting towards the radiator. The one towards the fan ran a vacuum line to the carb. The one that pointed back towards the firewall ran a vacuum line to the dist, and the one on the back that pointed up ran a line to the snorkel air cleaner.

The vacuum line to the snorkel on the air cleaner hooked up to the thermal sensor for the thermac valve in the air cleaner snorkel.

I'm not sure about the 396 application of this but this is how it was in my 307. I have since replaced the stock snorkel with an open 14"x3" cleaner, and ran a line straight from the carb to the dist.
Not sure if this helps you or not.
Fred
p.s. - I had a neat little diagram typed up for you, but my fonts are messed up and couldn't do it correctly.

[This message has been edited by Riffers70 (edited 04-28-99).]

The cylindrical part is called a solenoid. It is for the TCS system, short for Transmission Controlled Spark. What it does, is controls the vacuum to the distributor. The other components of the system are thus...On the firewall there should be a relay with a dark green, dark blue, and black wires in a plug on it. In the right (passenger) side head there should be a switch with a dark green wire to it, and a second dark green wire jumpered to the second term. on switch. If your car is a 4-speed, there should be a switch on the front of the trans side cover. If automatic, there's a switch in the trans, and the harness for the kickdown has a second wire in it.
The way it works, is, when the car is cold, or overheating, the switch in the right side head grounds the relay and allows full vacuum to the distributor. when the car warms to operating temperature, the switch opens up, and the relay is then controlled by the transmission switch. The relay then is only energized by the trans being in high gear. This was an attempt to reduce emissions. The net effect is the engine has no vacuum advance in the first couple of gears, or at idle.
For the best performance, just bypass it and run full manifold vacuum to the distributor.

Riffers70 & Dave B,

Thanks for your help! After reading your posts and taking a look at the configuration under the hood it appears my solenoid has already been bypassed. Although, fixing this appears to be an all show and no go, I am trying to keep the car original and will probably switch it back. Now all I have to do is find a solenoid (mine doesn’t appear to be intact)

Thanks again,
this site is great reference!!!!