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Topic: Heat Riser

in Forum: C3 Fuel, Emission Control, and Exhaust Systems


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Heat Riser (1/8)
 10/27/08 1:12pm
sundew
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Eagan, MN - USA

Vette(s):
Gone, but not forgotten: 1974 Coupe Red, matching numbers, Black Interior, L-48 w/ 4 speed; The “Admiral”, also gone and never to be forgotten. 1994 Admiral Blue LT-1 coupe, Black Interior Automatic


Joined: 6/18/2007
Posts: 427

This is probably the most basic of questions. I have developed a leak in my exhaust system. It was real easy to track down. The system is leaking between the manifold and the exhaust pipe on the right side of the motor. I believe this is in the vicinity of the heat riser valve. Why is this valve in the exhaust system and what is it's purpose? 



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Heat Riser (2/8)
 10/27/08 1:20pm
VetteSpecialties
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Mounds View, MN - USA

Vette(s):
70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe


Joined: 5/24/2007
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It is there so you can drive your Corvette in the winter!  When your engine is cold, the valve closes, forcing exhaust through the head, across the bottom of the intake manifold, and under the carb to warm it up.  They make a heat riser eliminator that is just the housing with no holes or valve in it.  There is a gaskey between the manifold and riser, and a donut on the end of the pipe.  Replace them both to be sure.

Larry
Heat Riser (3/8)
 10/27/08 1:37pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 20126

Yeah...what Larry said...
You can replace your riser with a new one if it is burned beyond repair, or frozen shut/open, or you can simply install the "eliminator" type. You can't just remove the valve, and bolt the exhaust back up to the manifold, you have to have the heat riser, or the spacer/eliminator.
If your valve is free, as in it moves open/close easily, then you prolly only need the gasket and/or the dognut...
Adams' Apple2008-10-27 10:39:36

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Heat Riser (4/8)
 10/27/08 3:13pm
sundew
Former Member

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Eagan, MN - USA

Vette(s):
Gone, but not forgotten: 1974 Coupe Red, matching numbers, Black Interior, L-48 w/ 4 speed; The “Admiral”, also gone and never to be forgotten. 1994 Admiral Blue LT-1 coupe, Black Interior Automatic


Joined: 6/18/2007
Posts: 427

Thanks, guys.....now the fun starts....gettin' the bolts loose without breakin' 'em off!

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Heat Riser (5/8)
 10/27/08 3:40pm
Ron 78Lifetime Member
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BINGHAMTON, NY - USA

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Joined: 7/19/2003
Posts: 3808

Soak the snot out of them with P.B.Blaster for a couple of days,also soak the bolts that hold on the exhaust manifold.ya prolly aint gonna get all 3 bolts off at the pipe wid out breaking at least 1 offConfused.this way you'll be 1 step ahead when ya have to take the exhaust manifold and take it to a muffler shop an get all 3 bolts replaced,don't forget when you put the stuff back together ,get yourself some of the longer BRASS nuts,made for exhaust mounting just tell the guy ,he'll know what you want.I'm not tryin to jinx you on this job,but ya may as well plan for the worst,ya might luck out ,but I wouldn't bank on it LOL Ron 782008-10-27 12:41:43

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Heat Riser (6/8)
 10/27/08 10:49pm
kstyerLifetime Member
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CUYAHOGA FALLS, OH - USA

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1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!


Joined: 12/2/2003
Posts: 6424

First, the heat riser does what Larry says.  The reason is faster warm up of the intake to create better fuel atomization and easier operation during warm up.
 
I use my fire wrench (torch) to turn the nuts orange before even trying to turn them.  That takes them right off.  Okay, for some of you I'm cheating, but it does the job quick and easy.
Heat Riser (7/8)
 10/28/08 9:44pm
acplus
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, - Canada

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1972, 1980


Joined: 6/23/2008
Posts: 558

If you don't have access to a wrench like kstyer fire wrench, you soak as suggested above, and start the motor and heat the exhaust up (go around the block) keep your hands away...really hot, and with a socket and extension, loosen the nuts.
John
Heat Riser (8/8)
 10/29/08 6:24pm
Ten15
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East Hanover, NJ - USA

Vette(s):
'68 Black Conv. Matching 327/300 4 Spd. P/S, P/B, P/W, Tele, A/C


Joined: 9/25/2004
Posts: 525

Wally,
 
If you want it, I have a 2" heat riser that has 1000 miles on it.  It looks good & works fine.  All you need is a new heat riser gasket & donut from the local parts store. 
 
I replaced it with a new one that I had welded into the open position.
 
Send me your address in a PM or E-Mail.
 
Anthony
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