what is this?
 

What does this thing do and do I need it on my Californian truck? I’m installing a new set of Edelbrock smog legal headers. Truck is a ’81 and Im in process of swapping out the 305 for a 350.

That is the valve/flapper which causes the exhaust from the passenger side of the engine to flow through the intake exhaust-crossover to warm up the intake manifold faster. I do not know if it is required for emisions, but it plays an important role in allowing the engine to warm up quicker alowwing less emissions so I would quess it is required.

Well I would call your Nazi's and check.

If your truck has electric choke it's proably not going to make a huge difference with it gone in temps above 40degrees. Here in GA they don't care about stuff like that. Hell they most of the time don't even lift the hood. All the verify is that all exhaust appears to go through a Cat and do an anal probe sniffer test. Cali...all bets are off.

it also depends on which county your in, when he lived in houston they did the probe, now that we moved north of beumont to silsbee, they don't care at all. does it have 4 wheels and stop? good enough to them.

Welcome to California. Yes you will need it. If the politicians have anything to say anyone with a 76 and up will always need it.

so does that black hose hook to a vacuum line? Is that the only connection? The lkinkage looks all rusted up. Should I replace it?

The proper name for the part is EFE valve. (EARLY FUEL EVAPORATION)

They are sometime called a heat riser. That was the name used on older vehicals for the spring style units.

The vacuum hose should connect to a thermovacuum valve that is usually on the thermostat housing. The other port of the thrmo valve should be connected to vacuum. No other connections.

Apply vacuum to it and see if it moves and holds vacuum. Also, the hole in the end of the actuator arm get worn and loose. They can rattle loud as they are moving from the closed to the open postion, if they are worn.

Yes, you need that here in CA. It needs to hook up to a canister, then the canister hooks up to full vacuum on the carb, then the other side hooks up to the Temp Control Valve on the Air Intake tube. It's all part of the THERMAC system. (Air Intake, Heat Choke Stove Tube, Heat Riser valve)

I agree the Smog-Nazis will want you to have this fine piece of memorabilia. It is a real dinosaur from the past. The new cars are better at smog and most of them don't have to use this.

just smogged my cali '77 sbc400 truck today. passed!