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That’s your heat riser to your Auto Thermac system. It provides hot air from around the exhaust to enter the air cleaner to help warm up the engine.
Chances are you’re not driving your car in very cold conditions. I would remove that tube and lock the flap inside the air cleaner in its fully open position.
very nice original looking engine.. I would replace it. unless it never gets cold as you have no location.
it tries to control the combustion air temperature by opening and closing that flapper. i think around 130f to 120f for drivability and lower speed efficiency. On an L82 full throttle bypasses this with another hose with only fresh air (see video)
or just pretty it up on the dents.. i am sure it still works fine without major holes/ rips..
Thank you both. I’m in Pennsylvania but I put it away for the winter so I really don’t drive it in cold weather. I’ve got an order going already with rock auto going to see if the have it.
Thanks, Dave
very nice original looking engine.. I would replace it. unless it never gets cold as you have no location.
it tries to control the combustion air temperature by opening and closing that flapper. i think around 130f to 120f for drivability and lower speed efficiency. On an L82 full throttle bypasses this with another hose with only fresh air (see video)
or just pretty it up on the dents.. i am sure it still works fine without major holes/ rips..
Ok got the new hose on. Harder than I expected, I guess that thing is supposed to be tight but man it was a real &$@#% getting that on! Advanced auto showed it at 1 1/2” for my car and looked the same diameter as the one I removed but it was tough. Anyway that’s done, replace valve cover gaskets next.
Hey folks, update on this. So, my car tends to idle high for longer than it should after you start it. It eventually will go down but it takes a good ten minutes at least. I have tried hitting the gas quick and letting it go but it doesn't do anything. I was thinking that replacing the heat riser hose would fix this, but it didn't. I did check the flap on the air intake duct when I start the car and it is closed, so the warm air should indeed be coming up through the riser. Can I assume that the issue would be the temperature sensor on the air cleaner or could it also be something else?
Again, I reiterate that I am new to working on this stuff, so I apologize if these are dumb questions!
Thanks,
Dave
First of all, the high idle will stay on until your choke warms up. In an 80, that should happen with the electric choke. If it is adjusted correctly, it is basically a timer, which can make hot restarts challenging.
Is your choke working? Is your electric choke connected? Does it open fully after 20 minutes of driving? What is your steady-state operating temperature (you might need a IR temp gun for this).
Please take some photos of the top of the engine, and all sides of the carb, with the air cleaner assembly removed. The next step might be to email @lars and ask for his Timing, HEI, and Quadrajet papers, and pick up a copy of Cliff Ruggles' book.
Here's one of many threads on 80 Q-jets where @lars posted his email.
Hey folks, update on this. So, my car tends to idle high for longer than it should after you start it. It eventually will go down but it takes a good ten minutes at least. I have tried hitting the gas quick and letting it go but it doesn't do anything. I was thinking that replacing the heat riser hose would fix this, but it didn't. I did check the flap on the air intake duct when I start the car and it is closed, so the warm air should indeed be coming up through the riser. Can I assume that the issue would be the temperature sensor on the air cleaner or could it also be something else?
Again, I reiterate that I am new to working on this stuff, so I apologize if these are dumb questions!
Thanks,
Dave
The green sensor inside the air cleaner controls when the vacuum inlet ducts open. Essentially, it is a controlled vacuum leak.
A cold start on a 60-65* day my 77 takes about 5-6 minutes of run time before choke plate goes full vertical.
Do you have a hot air choke or electric? And is your choke plate full vertical and it still doesn't drop off high idle?
The EFE system helps the engine warm up faster. Seems your thermal vacuum switch is working so thats good.
If everything else checks out and is working as it should ,you can modify the choke coil so it can be adjusted for time. The 3 rivets are drilled off and the bosses are tapped for machine screws. You can then rotate the choke coil cover adjustment to speed up or slow down the choke time.
I had to do that on my '80. I took the EFE system off and the electric choke pulled off too soon. Choke coil mod got it just right.
