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I'm having duals put on today, and the "heat riser" (that's the only term I know to call it) is rusted so bad it fell apart. How critical is this to proper operation? I live in South Carolina, so not severe cold. Chevy dealer no longer lists it or the manifold. If my carb choke system is OK, will this matter?

Thanks,

H-dog
 

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Back in those good old days the first thing we did was wire this thing open. Tried to take it out but the pipes wouldn't line up just right so I would knock out the flapper and plug up the shaft holes. Never made any difference with cold weather driving, and it gets cold up here. If your pipes will fit ok, don't worry about it.
 

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You can get either the valve assy or the open spacer at your local NAPA store. they sell Walker exhaust parts. You definitely need something in there to take up the space.

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Leo Paugh
MCC #017
www.clark.net/pub/chevelle/mcc.htm
There are no strangers here, only friends you haven't met.
 

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The heat riser does two things - it heats the floor of the manifold to improve fuel/air atomization when the engine is cold and reduce "wetting-out" of fuel on the port walls, and it provides heat for the bimetallic choke stove next to the carburetor. Without a heat riser, the choke stove may not ever get hot enough to fully open the choke blade, resulting in poor fuel economy. Most Camaros I've seen without heat risers or with headers have the choke wired full open. I just replaced the heat riser on mine (stock exhaust system) and it markedly improved cold driveability and warm idle stability - with our weather, it's a necessity.

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JohnZ
'69 Z28 Fathom Green
 
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