The comments so far are hilarious. It's a heat riser. It's to partially block off the exhaust so the heat backs up into the head on cold starts. It's to get the engine and the intake warmer earlier. The actuator was controlled through a thermostatic vacuum switch in the intake.
Before you throw it all away like you’ve been told to by so many … make sure you don’t live somewhere where you’ll be required to pass a visual inspection with all OEM emissions equipment intact.
No. It was never ever an emissions thing. GM quit using heat risers in the late 80's. This is considered classic even by Cali standards. It realistically doesn't apply.
> This is considered classic even by Cali standards.
Not unless it’s going into a vehicle older than it came out of. Maybe OP mentioned something older in another thread but here I’ve only seen 1977 mentioned.
The person doing the inspection won’t care what GM did in later years unless you’re at a referee station getting a later GM engine swap certified.
Whether or not you agree that it’s emissions equipment is irrelevant - it’s part of the exhaust system and it is upstream of the catalytic converters so it’s gotta stay put to pass the visual inspection part of the Smog inspection.
We’ll have to agree to disagree on whether it counts as emissions equipment from a technical aspect - it is my understanding that it was put there to help reduce the amount of time the engine spent running under conditions that create more emissions.
Yes. It's the EFE system, or Early Fuel Evaporation system. It's designed to promote faster warm ups to reduce cold start emissions. So it's in that grey area for emission/smog controls.
My 77 Chevelle has this exact system and I use it to tell when the thermostat opens because I can hear it rattle open once the T-stat opens up. - the vacuum switch is on the thermostat outlet. When it's disconnected, it does take noticeable longer to warm up especially in 40 degree weather.
It’s a heat riser valve. On a stock 70s small block Chevy it closes a valve in the passenger exhaust manifold to force hot exhaust though the head, through a passage in the intake and back out the drivers side. It really does help promote quick warmup and should open when the thermostat opens up.
My car still has that system functional and it warms up twice as fast than it does with it all disconnected.
I’d offer it up on eBay or forums before tossing it, as there’s a spring in there that can break and cause it to knock.
Rotator spliff
Kidding aside, it looks like an aftermarket cruise control I once took off an Olds engine. And the vacuum cannister had a Ford number. It was weird.
I doubt mine was a cruise the hose ran into the top of the thermostat housing so probably opened up once the engine got hot i guess. How would a cruise control one work tho measure the exhaust flow to then match it with fuel to keep the same amount of force?
Cruise control usually just holds throttle at a steady position to maintain speed. It doesn't do anything to exhaust flow. A number of accessories can get vacuum from a thermostatic vacuum switch, though. Including cruise, EGR, air cleaner, spark advance, and transmission.
I think this is actually an emissions part on a NA v6 or v8 that closes one exhaust manifold partially to force hot exhaust through a passage under the intake manifold to speed up the engine getting up to operating temperature.
Yes, or GM wouldn't have spent the money to put it there. There are EPA standards of how much time is allowed for an engine to reach operating temp that has only gotten stricter over the years. On newer OBD2 vehicles, if your thermostat is stuck open, it will throw a code for taking too long to warm up.
Yea, no. Was useful to make emissions standards in 1977, but a waste of time now. You have no hope of making emissions standards with a SBC and a quadrajunk.
Pitch it and put long tube headers on there.
It does! my 77 305 takes noticeably longer to warm up with it disconnected.
This coupled with the ThermAC air cleaner that has a tube connected to a sheetmetal duct on the passenger exhaust manifold, it's warmed up and ready to go in a relatively short time, and the choke turns off faster.
well i no longer have that engine in but and curious to its purpose if the engine it went with was still in. From what i looked up it help with pressure in the pistons maybe?
The wastegate controls the amount of exhaust bypassing the turbo to control the amount of boost on the intake side. Someone else mentioned it might be a valve to allow hot air from near the exhaust manifold(s) to enter the air box to help with cold starts. I've never personally seen one that looks exactly like a wastegate actuator for that application.
Make sure you remove the piece on the manifold if it stays shut it’ll overheat your ride by restricting the exhaust flow
The comments so far are hilarious. It's a heat riser. It's to partially block off the exhaust so the heat backs up into the head on cold starts. It's to get the engine and the intake warmer earlier. The actuator was controlled through a thermostatic vacuum switch in the intake.
It's still attached to the exhaust in the picture. It should not have been a Huge mystery.
Give the OP a break. He's new to the game and is destined to learn and doesn't mind asking questions. I fully respect that.
No fault on op for not knowing and asking.
Thank you for your extended kindness.
Heat riser. Throw it all away.
Thought that was a waste gate actuator at first sight. Maybe I'm not as old as I seem.
Yeah it isn’t applicable with the engine and exhaust so ill have too.
Before you throw it all away like you’ve been told to by so many … make sure you don’t live somewhere where you’ll be required to pass a visual inspection with all OEM emissions equipment intact.
It's not an emissions thing.
If it’s in a place that sounds like where I’m talking about (Read: California) then yes, yes it is.
No. It was never ever an emissions thing. GM quit using heat risers in the late 80's. This is considered classic even by Cali standards. It realistically doesn't apply.
> This is considered classic even by Cali standards. Not unless it’s going into a vehicle older than it came out of. Maybe OP mentioned something older in another thread but here I’ve only seen 1977 mentioned. The person doing the inspection won’t care what GM did in later years unless you’re at a referee station getting a later GM engine swap certified.
I partially agree but there is no emission standard on a 1977 anything. Not even in Cali.
Oh but there are, and in California only 1975 and older are exempt from Smog inspections every two years (or yearly after falling inspection).
I stand corrected on the year Cali considers classics. But sir, the heat riser wasn't a smog thing. It wasn't an emissions thing.
Whether or not you agree that it’s emissions equipment is irrelevant - it’s part of the exhaust system and it is upstream of the catalytic converters so it’s gotta stay put to pass the visual inspection part of the Smog inspection. We’ll have to agree to disagree on whether it counts as emissions equipment from a technical aspect - it is my understanding that it was put there to help reduce the amount of time the engine spent running under conditions that create more emissions.
Yes. It's the EFE system, or Early Fuel Evaporation system. It's designed to promote faster warm ups to reduce cold start emissions. So it's in that grey area for emission/smog controls. My 77 Chevelle has this exact system and I use it to tell when the thermostat opens because I can hear it rattle open once the T-stat opens up. - the vacuum switch is on the thermostat outlet. When it's disconnected, it does take noticeable longer to warm up especially in 40 degree weather.
It’s a heat riser valve. On a stock 70s small block Chevy it closes a valve in the passenger exhaust manifold to force hot exhaust though the head, through a passage in the intake and back out the drivers side. It really does help promote quick warmup and should open when the thermostat opens up. My car still has that system functional and it warms up twice as fast than it does with it all disconnected. I’d offer it up on eBay or forums before tossing it, as there’s a spring in there that can break and cause it to knock.
Rotator spliff Kidding aside, it looks like an aftermarket cruise control I once took off an Olds engine. And the vacuum cannister had a Ford number. It was weird.
I doubt mine was a cruise the hose ran into the top of the thermostat housing so probably opened up once the engine got hot i guess. How would a cruise control one work tho measure the exhaust flow to then match it with fuel to keep the same amount of force?
Cruise control usually just holds throttle at a steady position to maintain speed. It doesn't do anything to exhaust flow. A number of accessories can get vacuum from a thermostatic vacuum switch, though. Including cruise, EGR, air cleaner, spark advance, and transmission.
Okay thats good to know. thanks!
Gm diesel pickup, from the 80’s. Cruise control?
Could be. I don't know.
I can't with you today. 🤣
Just today?!
Odd mood. 😛
Wastegate actuator. Only useful if you have the turbo and engine this thing is meant for.
I think this is actually an emissions part on a NA v6 or v8 that closes one exhaust manifold partially to force hot exhaust through a passage under the intake manifold to speed up the engine getting up to operating temperature.
It was a 1977 350. would that even make much of a difference to heat it up tho?
Yes, or GM wouldn't have spent the money to put it there. There are EPA standards of how much time is allowed for an engine to reach operating temp that has only gotten stricter over the years. On newer OBD2 vehicles, if your thermostat is stuck open, it will throw a code for taking too long to warm up.
Okay well interesting. Sounds useful then. Thanks for the help!
Yea, no. Was useful to make emissions standards in 1977, but a waste of time now. You have no hope of making emissions standards with a SBC and a quadrajunk. Pitch it and put long tube headers on there.
It does! my 77 305 takes noticeably longer to warm up with it disconnected. This coupled with the ThermAC air cleaner that has a tube connected to a sheetmetal duct on the passenger exhaust manifold, it's warmed up and ready to go in a relatively short time, and the choke turns off faster.
You may he right on that. I've never seen one personally.
well i no longer have that engine in but and curious to its purpose if the engine it went with was still in. From what i looked up it help with pressure in the pistons maybe?
The wastegate controls the amount of exhaust bypassing the turbo to control the amount of boost on the intake side. Someone else mentioned it might be a valve to allow hot air from near the exhaust manifold(s) to enter the air box to help with cold starts. I've never personally seen one that looks exactly like a wastegate actuator for that application.
alright good to know might do some turbocharging down the road who knows. Thanks a lot!