Heat Riser - Team Camaro Tech
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post #1 of 6 (permalink) Old Aug 16th, 02, 01:45 PM Thread Starter
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What is the real benefit of a heat riser? My 69 350 has original exhause manifolds with a heat riser on the right side. Seems like a heat riser would be too restrictive. Should I cut the butterfly flap from the shaft on the inside the heat riser or would it be best to just leave it alone? My car is not driven much in the Winter so my need for quick heat is not that important.
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post #2 of 6 (permalink) Old Aug 16th, 02, 05:01 PM
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The heat riser is part of the fast warm up system on a stock vehicle. The bimetalic heat sensor coil will force the butterfly at the rear of the passenger exhaust manifold to close, forcing the exhaust to flow from the passenger side of the engine up through the passage that is cast into the intake manifold and then out the drives side of the exhaust. On dual exhaust cars it frequently caused the passenger side to rust out very quickly when the valve would stick shut and that side was not brought up to full operating temperature and the water vapor rotted the one side out very quickly. Less of a problem on single exhaust cars.

The trick is to wire it open, or remove the butterfly, or replace it with the plain cast iron spacer used on fuel injection cars. The valves are very troublesome in many cases. If you don't drive much in cold weather and do not mind the extended warmup, this is a good modification. If you have headers you obviously do not have the heat riser butterfly valve anymore so you may want to block the heat riser passages between the heads and the intake. This is a good mod if you run an aluminum intake. With a cast iron intake it causes real long warm ups so maybe a restrictor would be better than a fully blocked passage.

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post #3 of 6 (permalink) Old Aug 17th, 02, 06:16 AM Thread Starter
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Does anyone know where I can get the cast iron spacer that stringr69 mentioned above?
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post #4 of 6 (permalink) Old Aug 17th, 02, 06:29 AM
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you can make your stock valve into a spacer. take out the shaft and butterfly, and maybe tap the holes for pipe plugs or use soft plugs like in the water jackets of your block. i would go with the pipe plugs. sometimes, you can just get a donut gasket and leave the spacer out altogether.

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post #5 of 6 (permalink) Old Aug 22nd, 02, 09:18 AM
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All the Corvette resto parts houses have the spacer - it was used on all F.I. Corvettes from '57-'65 (Corvette Central, Zip, Paragon, Dr. Rebuild, etc.).

'69 Z28 Fathom Green
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post #6 of 6 (permalink) Old Aug 23rd, 02, 05:55 PM Thread Starter
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I found a heat riser eliminator spacer at Rick's Camaro parts. Ordered it Wed and had it today (Friday). Just installed it with no problems. Thanks all.
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