xxx

 

I assume you mean wired in the open position? A quick way of fixing a non-functioning valve. It's purpose, if you are not aware, is to during warm up direct more exhaust gas through the intake manifold exhaust cross-over shortening warm up time.

 

xxx

 

You asked about the benefit, even if it was working. On cold start-up it is closed and deflects hot exhaust gases through the intake passages to the driver's side. This aids in heating the carb and smoothing the transition to a warm and stable engine running temp/condition. But it also leaves the passenger side exhaust system relatively cold and this hastens deterioration of the pipe and in particular the muffler as acidic liquid residues are not burned off in that warm-up period. Sound trivial but over time the "cold" passenger-side muffler falls victim to internal corrosion much more quickly than the driver's side. That is why people wire or weld the heat riser open: to get equal heat flow down both sides.

But under normal (untouched) conditions it can decide to corrode itself closed. Obviously not having exhaust flow down one pipe can very much impede performance and lead to an overheating condition on one side. GM in the day actually sold a rattle can heat riser fluid at the parts counter to prevent valve lock-up. If you can stand 5-10 minutes of smoke then PB Blaster does the same job today. I did it two weeks ago. Soak the valve, let sit for 30 minutes, and turn on the engine. The neighbours will love you!

 

Hi,
I've found that depending on just how the passeger's side muffler is tilted, and how well sealed the crimps in it are, you may see moisture dripping from it until the engine heats up enough to open the valve and heat up that side of the exhaust system.
Regards,
Alan


PS: Does an engine with the valve wired open not darken the paint on the intake cross-over that's so often seen?

 

Alan,

If you drill a 1/8" hole in the front most downwards point of the muffler you will be surprised how much fluid comes out. I do this.

 

Hi Paul,
Thanks!
It's been so many years since there were under car mufflers that I'm learning again.
Regards,
Alan

 

No, it's just the opposite. I wired mine open for the very reason your describing Alan...with the engine cold the valve is closed forcing exhaust through the intake cross-over, open allows exhaust to pass through the passenger side....so your wiring the counter weight down or open.

 

Hi gq,
I need to get this straight!
I thought having the riser wired open, would LESSEN, the darkening on the cross-over. I see now my question was confused.
Is that what you're saying?
Regards,
Alan

 

Alan, the darkening is caused by excessive heat to the intake and in extreme cases or over time it will burn the paint, just like it would on an exhaust manifold. The valve when cold and closed, forces all the passenger side exhust to go thru the intake manifold xover under the carb and out the driver's side exhaust.

Here is a pic of a never touched oem setup, it had gotten hot enough over time to burn the paint off and start some rust.

Second pic is of the same engine and manifold after the xover has been plugged, with about 5000 miles on that setup and of course washed and detailed. It should never turn dark or burn again. Choke has also been disabled as we really don't need it down here.

Third pic is an easy way to wire it shut.

 

Third pic is an easy way to wire it shut.

I think you mean open.

 

Are there any negative effects to wiring the valve open or replacing with a spacer? I recently replaced the spacer on my car with a new heat riser and it does not work correctly. It won't open after engine has heated.

 

i bought a new valve when I replacaed my exhaust.. after thinking it thru, I should have just bought a spacer..

http://www.zip-corvette.com/ProductD...GR-SR&CTitle=&