exhaust manifold

[Tuvlo]

I have a 79 k20 with the 350 and the passenger side exhaust manifold has a valve at the end of it, my guess it is there for the EGR but i dont know, but it is not connected to anything and rattles like no other when im not on the gas even after i used wire to hold it in place. My question is can i stop it from rattling or do i have to get headers?

[DrMaserati]

What you're describing sounds like the heat riser valve. It's supposed to be closed when the engine is cold and open as the engine warms up. It is entirely mechanical and should have no wires or hoses attached to it.

#1) The best option would be to find out why it's rattling and repair it if possible. Or just replace it.

#2) I've seen some people wire them open with baling wire to keep them from rattling. (easiest option)

#3) Another option is to cut the flapper valve out of it, tap the two shaft holes, and plug them with machine screws.

#4) A fourth option would be to remove it entirely. But if you do that the exhaust pipe will have to come up by the thickness of the valve and will probably hit the frame, requiring some mods to the exhaust on that side.

#5) Installing headers is another option. That eliminates the valve entirely.

Since you live in Colorado, where it can get quite cold, I think option #1 would be your best choice. Without the valve in place and operational it will be very cold blooded, and the choke will stay on for an abnormally long time in cold weather.

JP

[Tuvlo]

the valve has a little ball joint type fitting on it, does that connect to any thing and where is it? It would be nice to have it warm up on the -30f days

[DrMaserati]

It should have no fittings on it. It should look very similar to this.

http://www.ss396.com/mm5/graphics/00...HR-1180_sm.jpg

If it doesn't, then you're talking about something other than the heat riser, and based on your "little ball joint type fitting" description I can't identify what you're talking about. You'll either have to provide a photo or a better description.

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[Tuvlo]

The valve on my truck is built in to the manifold (i could be wrong about that) at the end near where the pipe connects Ill have to see if i can get a picture. But, i think your right about it being a heat riser valve becaue the manifold has a pipe that runs to the factory air box thous me thinking it was a primitive EGR. How does it work in the first place though?

By the way i love your quote

[Prerunner1982]

that looks about right, not exactly, but similiar. To keep manifolds and get rid of it, you may try to find older manifolds not equiped with them. I went with headers and ditched mine, along with the rest of my emissions equipment.

Where in CO are you? My parents live up there.

[Tuvlo]

I did a search and a few people dont think the valve helps that much at all. Is that true? The reason i want to keep the manifolds is because im a "poor college student" and have other things i need like a clutch and flywheel.

I live in gunnison for school, its a small town on the west slope, but i grow up in denver.

[Chevrolet4x4s]

Summit racing has headers for these trucks complete kits 86.95
Shane

[piecesparts]

The totally official reason for this thermostatic spring controlled flapper valve is to provide a slight backpressure on that side of the motor when it is started on a cold day. That allows a small amount of exhaust gasses to go up into the intake manifold on the heat riser section and heat the area under the carb. There are two things that accomplishes (1) to heat the fuel charge as it goes into the cylinders and (2) to heat the choke spring that was mounted in the earlier trucks intake manifold. This assisted in the choke in "Pulling Off" after being set by cold temperatures. Most of us eliminated this thing a long time ago.

[piecesparts]

The totally official reason for this thermostatic spring controlled flapper valve is to provide a slight backpressure on that side of the motor when it is started on a cold day. That allows a small amount of exhaust gasses to go up into the intake manifold on the heat riser section and heat the area under the carb. There are two things that accomplishes (1) to heat the fuel charge as it goes into the cylinders and (2) to heat the choke spring that was mounted in the earlier trucks intake manifold. This assisted in the choke in "Pulling Off" after being set by cold temperatures. Most of us eliminated this thing a long time ago.

[swervin ervin]

I'm not exactly sure when they started using these valves with vacuum hooked to them but my 85 was this way. It had a vacuum line hooked to it routed through the temp vacuum switch. When the switch reached the correct temp it would open up the vacuum to the vacuum pod on the heat riser valve. I know older ones worked simply off of a thermostatic coil spring.

Anyway, the sole purpose of these valves were to reduce emissions. They helped by getting heat to the intake and choke quicker and thus help stop wasting gas. A cold intake lets the fuel stick to the inside in droplets and not vaporize as it should. The valves also helped with cold driveability.

If the valves worked right and didn't stick, they were a good thing to have on stock engines. But as stated, when they don't work right, they are a menace. Almost every vehicle I have ever owned with one, I removed. You can remove it safely but you will need to plug the hole left in the exhaust manifold where the shaft was located. Or, you can just wire it open and call it good until you get the money or time to do it right.

[Tuvlo]

Thanks for all the quick replies. i dont like the idea of wasting $3.15 gas but i guess ill take it out. Atleast i have a block heater to help warm things up quicker in the winter.

[swervin ervin]

If it's rattling, it's probably broken anyways. Taking it out might improve your mileage. Especially if it was not opening up like it should be.

Just a word. You can't just take it out. You will have no way of hooking the exhaust pipe back up to the exhaust manifold.

[Tuvlo]

Thanks swervin. I know i cant just take it out, as a matter of fact i dismantelled it last night and my dremal blow up, shocked the snit out of me and i had to finish with a hacksaw.