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Working late + hungry stomach + dinner (and annoyed wife) waiting for me at home = spirited drive home!
Unfortunately, I think I got too spirited because I apparently melted a vacuum hose! Well, not me, but the hot exhaust manifold melted the hose.
As I got off the freeway at the end of my, ahem, spirited drive - I smelled something burning. Uh oh. So when I got home a few minutes later I popped the hood (in the dark) and something was glowing! Yeah, that's a new one.
So what is it and what's it for? It's on the passenger side of the engine, coming from the carburetor I believe (I only did a brief visual inspection - it was cold and I was hungry) and down to a diaphragm near under the manifold near the dipstick.
V.H.......nice glow there..............it beats me as to what the hose controls.......
A thing I learned in military aviation is to do a "walk-around".....
(take a look at the vehicle/aircraft to see if everything is O.K.)
Sometimes we can spot a potential problem.....it's not an easy habit to get into, but it pays for itself the first time we "stop a gremlin" from causing a part-failure on our "ride".
If you're not an NCRS "kind of" guy, you could put a metal tube in that area with a radius-bend in it to give clearance around the E-manifold/connect the rubber hoses to each end of the metal tube to prevent future "glow-in-the-dark-problems....LOL.
Last edited by doorgunner; Dec 16, 2014 at 06:50 AM.
If you're not an NCRS "kind of" guy, you could put a metal tube in that area with a radius-bend in it to give clearance around the E-manifold/connect the rubber hoses to each end of the metal tube to prevent future "glow-in-the-dark-problems....LOL.
not a bad idea. i'll dust off the shop manual and see what that hose is - sounds like i have some quality time under the hood this weekend.
Retarded timing makes the exhaust manifolds really hot. What kind of timing are you running?
Doesn't seem like that should have gotten hot enough to burn given it's distance from the manifold.
It looks like part of the smog pump plumbing that goes into the exhaust manifold. It pumps air into the manifold. I wonder if it is cracked and leaking hot exhaust gasses, made hotter by the smog pump pushing fresh oxygen into the exhaust stream: if it's running rich you have a mini blow torch there.
I'm not positive that it applies here but that glow looks uncomfortably close to the mechanical fuel pump or its supply/output fuel lines...
No vehicle and especially one of our beloved C3's should suffer the fate of an underhood gasoline fire due to gasoline vapors escaping their protected path.
To the OP, please let us know what solution you employed to prevet a repeat of your picture taking. Looks too close for comfort.
That is the vacuum line to the heat riser valve, which in 1980 was operated via vacuum instead of the thermostatic coil. 1980 corvette vacuum systems are clearly not my strong suit, but I would expect that vacuum line to becoming from some sort of temperature vacuum switch, possibly on the intake manifold or water outlet. It helps your motor warm up faster - part of the emissions system.
That routing is curious - between the exhaust manifold and the A.I.R. tube. But, like I said, I am not familiar with 1980 corvettes.
Well, I was interested to see how that is supposed to run. It looks like it is supposed to be tubing that is held away from the exhaust manifold via a clip that is supposed to be at the valve cover bolt. Here is a link to a picture on Paragon's website.
Looks like it is the tube to the vacuum operated heat riser valve....not sure that part is still avalible, I would make a fix using some silicone vacuum tubing and heat shielding covering over it.
Well, I was interested to see how that is supposed to run. It looks like it is supposed to be tubing that is held away from the exhaust manifold via a clip that is supposed to be at the valve cover bolt. Here is a link to a picture on Paragon's website.
That's helpful, LeMans. Thanks for investigating - seems like I'm missing that clip. I'm going to replace the damaged vacuum hose this weekend and see if I can keep it away from the manifold.
Originally Posted by Solid LT1
Looks like it is the tube to the vacuum operated heat riser valve....not sure that part is still avalible, I would make a fix using some silicone vacuum tubing and heat shielding covering over it.
Well, I don't think I need to replace the riser valve, right? But, yes - silicone vacuum tubing is a good idea. I'll see what I can find this weekend and I'll keep an eye on it once I replace the hose.
Originally Posted by REELAV8R
Retarded timing makes the exhaust manifolds really hot. What kind of timing are you running?
Doesn't seem like that should have gotten hot enough to burn given it's distance from the manifold.
Couldn't tell you as the shop I use set it up. But I'm all ears...
Originally Posted by lurch59
It looks like part of the smog pump plumbing that goes into the exhaust manifold. It pumps air into the manifold. I wonder if it is cracked and leaking hot exhaust gasses, made hotter by the smog pump pushing fresh oxygen into the exhaust stream: if it's running rich you have a mini blow torch there.
You're saying I may have a crack in the manifold? That's a possibility, now that I think about it, given that not only was the hose severed but it continued glowing red hot for several minutes. I'll keep an eye on it once I replace the hose.
If you didn't live in California you could get rid of that heat riser.
I didn't even know it existed until this morning. As long as there's no negative impact on performance I'll leave it on there. But as soon as the 1976-newer smog requirement law changes here in California (we're almost there) then all bets are off!
Originally Posted by 7T1vette
Rubber hoses, electrical wiring and fuel lines are NOT good items to be anywhere near the exhaust manifold. Glad no fire started with this event.
True!
About two years ago I kept smelling gas but couldn't find the source, until I looked under the hood while the engine was running and saw gasoline leaking from the fuel pump. I immediately bought a fire extinguisher and drove (puckered) to my mechanic.
Make sure your heat riser valve isn't stuck shut. It will cause the passenger side exhaust manifold to be hotter and is not good for the engine long-term.
Didnt know the smog laws were supposed to change out here whens that going to take place?
Nothing official - don't want to get your (our) hopes up, but... There was a bill (S.B 1224) presented in 2012 that proposed changing the smog exemption from pre-1976 vehicles as it is now to pre-1981 vehicles (sorry to our brothers with 81-82 C3s in Cali) . The bill lost on a 3-4 vote, but that shows that there is some support and a strong possibility of it passing if reintroduced again in the near future. More info:
http://www.semasan.com/page.asp?content=aa_2012CA4&g=SEMAGA
Originally Posted by JimLentz
Make sure your heat riser valve isn't stuck shut. It will cause the passenger side exhaust manifold to be hotter and is not good for the engine long-term.
Good to know, thanks for the heads up - I'll check it out.
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.
Red Hot: Spirited driving = melted hose!
