Re: Straight eight manifold flapper

Posted by Owen_Dyneto On 2019/7/28 16:45:29

If you search on exhaust manifold heat riser valve, you'll probably find 100 posts about it. It's purpose is to improve engine performance at cold start up by using heat to improve fuel vaporization by deflecting hot exhaust towards the base of the carburetor. When it works properly, the thermostatic spring relaxes as the engine warms up and the counterweight drops, changing the position of the valve to "open" so the exhaust is blocked from the intake and passes directly into the exhaust header.

Sure, failure of the valve to perform correctly causes engine performance issues like vapor lock. Many owners, especially those in warmer climates, often either wire the valve permanently open, or even eliminate it. I use my cars in cool weather and a properly functioning valve does enhance performance during warmup, if it wasn't important to good performance, it wouldn't be there in the first place and I recommend repairing if necessary and keeping it functional.

PS - you're a fast man at the keyboard Howard, beat me to the draw again.