Quiz.....what are these?

[Green Monster]

Plug, female end. Is part of that bundle of wires wrapped in plastic, but it's sticking out. Right at the top of the bellhousing, below and behind distributor.

Cable, possibly e-brake? This is the end that's sticking out, near the speedo cable. But this runs on the outside of the frame, then goes through to the inside.

Valve thing on passenger side exhaust manifold. Can't get it to turn, I imagine it's restricting the flow.
Plugged hole on top of tranny

 

[76zimmer]

What year truck are we looking at, 70's?
1) possibly the oil sending unit on top of the block
2) parking brake cable adjuster
3) exhaust heat riser...helps the engine heat up quicker by blocking off the exhaust gases and sending the heat towards the air cleaner
4) vent

 

[Green Monster]

What year truck are we looking at, 70's?
1) possibly the oil sending unit on top of the block
2) parking brake cable adjuster
3) exhaust heat riser...helps the engine heat up quicker by blocking off the exhaust gases and sending the heat towards the air cleaner
4) vent

Thanks. So #1 should be hooked to a wire that goes to an idiot light or gauge, right? I ordered a new parking brake cable, so I assume it just attaches to that end? And the heat riser isn't hooked up to the air cleaner, so should I find the part that does that and hook it up? I think it's a metal, flexible hose, right?

 

[76zimmer]

What year truck?????

1) The plug end of that wire should hook up to the sending unit on the block, behind the distributor. If that is not it, then look for a sending unit in the vacinity that mates with that plug.

2) there should be a cable that goes to each rear wheel, IIRC they both come up to that adjuster cable.... like this:

The heat riser just blocks off the exhaust until the engine gets some heat in it, then a temp switch ( I believe on the intake manifold) opens and allows vaccum to pull open that heat riser for regular exhaust flow. The exhaust manifold should have a piece of tin on it with a hook up for a corrugated metal tube that goes to the air filter....It should look like this:

 

[frankin5]

If it is new than 75 you need the heat riser valve as part of your smog. It cause the exhaust on the passenger side to flow thru the manifold until it reaches operating temperature. It fits between the exhaust manifold and the cross over pipe and is vacuum operated by a thermostatic valve on the intake manifold.

 

[76zimmer]

also if someone put a different oil pressure gauge in the truck, they may have put a different oil sending unit in the block, or even used a metal or plastic tubing type on the block.

 

[Green Monster]

What year truck?????

1) The plug end of that wire should hook up to the sending unit on the block, behind the distributor. If that is not it, then look for a sending unit in the vacinity that mates with that plug.

2) there should be a cable that goes to each rear wheel, IIRC they both come up to that adjuster cable.... like this:

The heat riser just blocks off the exhaust until the engine gets some heat in it, then a temp switch ( I believe on the intake manifold) opens and allows vaccum to pull open that heat riser for regular exhaust flow. The exhaust manifold should have a piece of tin on it with a hook up for a corrugated metal tube that goes to the air filter....It should look like this:

That LMC guide is great, I should have thought of that. It's a 76. I've seen the heat riser tube before, so I can find it. Thanks for your help!

 

[Green Monster]

What year truck?????

1) The plug end of that wire should hook up to the sending unit on the block, behind the distributor. If that is not it, then look for a sending unit in the vacinity that mates with that plug.

2) there should be a cable that goes to each rear wheel, IIRC they both come up to that adjuster cable.... like this:

The heat riser just blocks off the exhaust until the engine gets some heat in it, then a temp switch ( I believe on the intake manifold) opens and allows vaccum to pull open that heat riser for regular exhaust flow. The exhaust manifold should have a piece of tin on it with a hook up for a corrugated metal tube that goes to the air filter....It should look like this:

Hold on, I just looked at your picture again. This valve is at the end of the exhaust manifold, not the center. It goes on at the end of the collector, where the exhaust pipe bolts on.

 

[76zimmer]

correct, right where the head pipe bolts on...the heat riser block goes between the manifold and the head pipe. The heat stove shown in the picture is usually screwed to the exhaust manifold and has a flexible metal hose that goes to the air cleaner intake tube (that points toward the pass side headlight area) The heat from that stove is used to warm up the carb quicker.

 

[Green Monster]

correct, right where the head pipe bolts on...the heat riser block goes between the manifold and the head pipe. The heat stove shown in the picture is usually screwed to the exhaust manifold and has a flexible metal hose that goes to the air cleaner intake tube (that points toward the pass side headlight area) The heat from that stove is used to warm up the carb quicker.

Ok, maybe I'm confused, so bear with me. Your picture shows the heat stove going to the exhaust ports on cylinders 4&6, correct? The valve I have is located at the end of the runner. Referencing your picture, it would be all the way to the left, past #8 cylinder at the end of the collector. So would this heat stove go all the way down there? I've seen them like you've drawn, but never seen a flexible metal pipe go all the way down there. Sorry if I'm confused, and I appreciate your help!

 

[diesel4me]

The "stove" is just stamped sheet metal that is screwed or riveted around the exhaust manifold like a jacket,around the middle of the manifold...a "crinkle" foil laced paper tube connects the stove to the air cleaner housing to allow the heated air to enter the air filter housing and the carb...Chevy started using the "Thermac" air cleaner around 1968 for emissions and better cold driveability..

 

[76zimmer]

Yep that!
That cast iron flapper valve (heat riser) goes where I said it does earlier.
And Bobs pic of the heat stove tin around the center of the manifold is where that heated tube goes up to the air cleaner horn

 

[Big Ray]

I've seen the riser tubes in the Help! section of various parts stores...

 

[Green Monster]

Thanks guys. I'll revisit in a couple of days, and I'll post some pics.

 

[Green Monster]

OK, I finally had a chance to look at this again today. Check out these pics and tell me what you think. As you can see, there is no contraption on the exhaust manifold for a stove, and this valve goes on the collector. This truck passed smog as is, no modifications have been made. Thinking of just cutting the butterfly out of the center of the valve and reinstalling. Thoughts? Again, it's a 76, CA truck so it has the smog pump. No cats. And there is nothing that attaches to the exhaust valve that makes it move.

 

[dyeager535]

I'm not sure it would have a heat riser. The Thermac (the circle on the air cleaner snorkel that has a vacuum line running to it) is specifically there to close the inlet to outside air and force the engine to ingest warm air off the exhaust manifold. I don't believe any truck from the mid 70's had that setup. Could be wrong, those aren't my years, but from everything I remember seeing of 70's trucks, they had an air cleaner housing with an open air inlet under the hood. The one you picture is designed to attach to a cold air tube from the core support. If nothing else, make sure the valve in the air cleaner inlet is open on the air cleaner when the engine is running and up to operating temp.

The heat riser valve works the same as a choke coil. As it warms up, it opens. Unless it is frozen in that position. I have never taken one of those apart, but if you are considering it, make sure the valve (butterfly) isn't all that is holding the shaft in the housing. It may be.

 

[Green Monster]

I'm not sure it would have a heat riser. The Thermac (the circle on the air cleaner snorkel that has a vacuum line running to it) is specifically there to close the inlet to outside air and force the engine to ingest warm air off the exhaust manifold. I don't believe any truck from the mid 70's had that setup. Could be wrong, those aren't my years, but from everything I remember seeing of 70's trucks, they had an air cleaner housing with an open air inlet under the hood. The one you picture is designed to attach to a cold air tube from the core support. If nothing else, make sure the valve in the air cleaner inlet is open on the air cleaner when the engine is running and up to operating temp.

The heat riser valve works the same as a choke coil. As it warms up, it opens. Unless it is frozen in that position. I have never taken one of those apart, but if you are considering it, make sure the valve (butterfly) isn't all that is holding the shaft in the housing. It may be.

Thanks. I'm drawing the same conclusion. This thing is certainly frozen. Won't budge. Think I'll either bend it open, cut it out, or just cut the butterfly wings off and leave the shaft. And it doesn't connect or interact with anything else.

 

[76zimmer]

can you hook up your exhaust head pipe without the heat riser valve in between them?

 

[diesel4me]

In a warm climate I would not worry about the heat riser,I have cut the butterfly out of a few and only noticed a difference in the winter,when the carb needs extra heat to prevent icing up...some vehicles over a certain GVW were emission exempt and had none factory too..

Older heat risers had the thermostatic coil thing like a choke ,ones after 1975 or so used a vacum can to operate the butterfly,it was controlled by a ported vacuum switch in the thermostat housing or intake,that denied vacuum to it once the engine reaches operating temperature..

I think the Thermac air cleaner was used from around 1968 to 1976..some states may not have gotten them,usually colder climates required them more..

You'll probably need the heat riser (minus the flap) as a spacer,to allow a stock exhaust pipe or y-pipe to fit properly,maybe not,only way to tell is try fitting them up without it..

 

[dyeager535]

can you hook up your exhaust head pipe without the heat riser valve in between them?

No, the exhaust manifold is flat where it mates up, instead of tapered for the typical exhaust expanded joint. I'm sure there is a way to get around it, but probably easier/cheaper to modify the valve than to come up with a replacement.

They make spacers for these, used in Corvettes a few years as a matter of fact.