Heat riser valve.

[y5mgisi]

On my Blazer on the passenger side exhaust manifold, there is a heat riser valve at the collector. All i really need to know is if is opens or closes when vacuum is applied to the diaphragm. I have a hunch mine is staying closed.

Kinda like this one but vacuum operated.

 

[imiceman44]

Well it is supposed to open when the engine warms up so one was to find out is to see if the vacuum switch that give it vacuum is open when cold or closed.
If you are trying to determine if that switch is working then see if it has vacuum when cold then try it when warm.
My 84 had that but I think it was closed and when the engine was cold and when warmed up the vacuum switch would open and vacuum opens it.

On my Blazer on the passenger side exhaust manifold, there is a heat riser valve at the collector. All i really need to know is if is opens or closes when vacuum is applied to the diaphragm. I have a hunch mine is staying closed.

Kinda like this one but vacuum operated.

 

[y5mgisi]

Cool! Thats all i needed! THanks!

 

[y5mgisi]

Here is mine just for fun.

 

[4X4HIGH]

It's been too long for me to remember but what I liked to do was to cut the flapper out and then put the valve back and this way there is NO CHANCE of it ever being closed. This was only to help the engine warm up faster in the morning and to please some smog Nazi somewhere. Oh, you never heard me say anything about removing or modifying an emissions item.

 

[y5mgisi]

you got it! Honestly, thats what i would like to do with it. The funny thing is i figured you would be the guy telling me to keep it!

 

[4X4HIGH]

you got it! Honestly, thats what i would like to do with it. The funny thing is i figured you would be the guy telling me to keep it!

Nope, i'm not against pulling emissions stuff off it's just the people who bitch about it if/when they get caught for doing so that bothers me.

 

[y5mgisi]

Ah i see. Might i ask what your opinion is on EGR valves?

 

[4X4HIGH]

Ah i see. Might i ask what your opinion is on EGR valves?

I would leave it on. They help reduce cylinder temps which helps to reduce chances of detonation.

 

[y5mgisi]

Got it. What would you do about one thats causing stumbling and such? Like say, taking off lightly from a stop sign it causes a stumble. And if you un hook the vacuum line that goes to it, the problem goes away. Any ideas there?

 

[diesel4me]

The vacuum operated heat risers need vacuum applied to CLOSE the butterfly,and have a spring that holds it open at all other times--the vacuum comes from a temparature cintrolled ported vacuum switch thats located in the intake manifild or thermostat housing..if you take off the vacuum hose to the heat riser it will stay open,so long as the spring inside the diaphram housing hasn't rusted away or broke (extremely rare)..

I'd leave this on the engine and keep it functional--when cold this valve closes and forces all the exhaust gasses from the passenger side of the engine to flow through passages cast into the bottom of the intake manifold under the carb,and out to the other head,which heats up the carn & manifold,and which vaporizes the fuel./air mixture better and reduces warm up times and improves gas mileage and lowers emission,it also prevents cold weather carb icing,which is something I had a lot of troubles with when I had an Edelbrock carb on my 305 in a 79 Bonanza I had--I would have to rig up a vacuum source to keep the heat riser valve closed all the time,plus have the "heat stove" hot air pipe from the exhaust manifold to the air cleaner in the "heat on" position all winter long until temps climbed above 50 degrees,or the dam thing would stall out at every red light,due to carb icing...

 

[EIB8400]

My little flapper thing was stuck so I cut the flapper out and bolted everything back together. Seems to run fine for me.