Exhaust heat riser valve

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Jul 28, 2009 | 08:57 AM

Rally68

Thread Starter

Burning Brakes

Joined: Sep 2008

Posts: 805

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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!

Jul 28, 2009 | 10:08 AM

7T1vette

Team Owner

Joined: Jan 2006

Posts: 37,637

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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.

Jul 28, 2009 | 02:30 PM

69Vett

Safety Car

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From: Austin Texas

Corvette of the Year Winner 2017

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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

Jul 28, 2009 | 03:33 PM

Alan 71

Team Owner

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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

Jul 28, 2009 | 06:33 PM

7t3shark

Instructor

Joined: Apr 2007

Posts: 184

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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.

Jul 29, 2009 | 09:06 AM

Rally68

Thread Starter

Burning Brakes

Joined: Sep 2008

Posts: 805

Likes: 5

From: Naperville Illinois

Quote:

Originally Posted by Alan 71

That's what I'm thinking. I hope it's that simple. I'll get to the bottom of it this weekend.

Until then, I'm disturbing the peace

Jul 29, 2009 | 10:05 AM

TimAT

Le Mans Master

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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.