Exhaust heat riser valve
Thread Starter
Burning Brakes
Joined: Sep 2008
Posts: 805
Likes: 5
From: Naperville Illinois
Exhaust heat riser valve
After re-assembling my exhaust I have a pretty noticeable leak where the heat riser is on the passenger side. I didn't disassemble that joint but was moving the exhaust around a bit, taking it apart and putting it back together. I'm clueless about this part.
What does the valve do?
Does it need lube/maintenance?
I've seen where vendors sell spacers to replace the valve; is this a good or bad idea?
Lastly, will I ruin anything (gasket, etc.) if I try tightening this joint?
Thanks!
What does the valve do?
Does it need lube/maintenance?
I've seen where vendors sell spacers to replace the valve; is this a good or bad idea?
Lastly, will I ruin anything (gasket, etc.) if I try tightening this joint?
Thanks!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
That valve is meant to [partially] close off the exhaust flow on the right bank to force heated exhaust up into and across the intake manifold for heating the carb choke. That valve has a bi-metallic spring on it which unwinds as it heats, so that it will open the valve completely once the engine is warmed up. To keep the valve from locking up, it needs to be lubed...but it has to be very hi temp lube or graphite product [dry lube]. The shaft is all that needs to be lubed. To test, just move that counterweight up and down to be certain there is freedom of operation. If the heat riser is leaking exhaust, someone didn't install the 'donut' gasket to it.
Safety Car
Joined: Oct 2007
Posts: 3,729
Likes: 267
From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
they make a spacer to eliminate the heat riser completely,
I suggest that if you live in a warm climate, with min. cold weather. 69VETT
I suggest that if you live in a warm climate, with min. cold weather. 69VETT
Team Owner
Joined: Sep 2006
Posts: 31,283
Likes: 4,373
From: Westminster Maryland
Hi R68,
There's a packing 'donut' and a sheet metal extension 'sleeve' that fit in the connection between the heat riser, and the head pipe. Did they get moved around a little so they're not giving the seal you had before disassembly?
Regards,
Alan
There's a packing 'donut' and a sheet metal extension 'sleeve' that fit in the connection between the heat riser, and the head pipe. Did they get moved around a little so they're not giving the seal you had before disassembly?
Regards,
Alan
Instructor
Joined: Apr 2007
Posts: 184
Likes: 1
From: Atlas is shrugging KC, MO area
You can also easily wire it open. First thing I did after picking up and never had any cold weather driveability problems. Later when had intake manifold off, blocked off the crossover passage to keep carb cooler after engine was warmed up.
Thread Starter
Burning Brakes
Joined: Sep 2008
Posts: 805
Likes: 5
From: Naperville Illinois
Until then, I'm disturbing the peace
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
If you want to lube it, there's a product called "Mouse Milk" Works great in Hi-Temp applications. Used on small turbocharged aircraft to lube the turbo wastegate.
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