55.2-59 Counter weighted rotation thingamajig in exhaust???

[BlouDon]

What is the Counter weighted. coil spring loaded, rotation thingamajig in the exhaust manifold just below the carb???

What is it meant to be doing?

What would happen if one were to remove that?

[jwhotrod]

heat riser feeds hot exhaust to the carburetor.

[nvrdone]

sounds like what you are talking about is the heat riser valve. on my 327 it was in the right exhaust below the exhaust manifold. there was a tube from the manifold up to the choke on the carb. this provided heat causing the carb to warm up. I removed mine when I installed the block hugger headers and changed over to an electric choke. check ebay - they have pictures. look under 55 chevy pickup exhaust parts.

[geezer#99]

Yes it’s a heat riser or heat diverter.
Deflects some hot exhaust on to the underside of the plenum on your intake. The plenum is that area on your intake right below the carb. The heat helps to keep the fuel vapor atomized. Cold fuel vapor will revert back to larger fuel droplets. You’ll get some lean misfires without it. The Chevy six takes a long time to heat up without it.
If you don’t mind a rough running misfiring motor until the motor gets up to temperature then remove it.
If your ambient temp is always above 10C you could remove it. Hotter air intake helps.

[BlouDon]

Thank you! Should I entertain any thoughts of a few more torques by removing this diverter?

[nvrdone]

im not sure it would improve performance. just helps the engine warm up quicker

[geezer#99]

Wire it in the open position and see how you like it.

[Dan in Pasadena]

Thingamajig, whatchamacallit, chingadera in Spanish.

[mr48chev]

Originally Posted by geezer#99

Wire it in the open position and see how you like it.

That would be the indicator.

As long as the bi-metal spring is working correctly and opens the valve as it is designed you have smoother less hassle free driving when the engine is cold and it isn't an issue after it is open. The key is that it does work and the valve does move. The counter weight should help it open along with the spring.
If you block it open or even remove it and put a bolt or pair of bolts in the holes (stuck though from the inside with nuts on the outside. It tends to act like headers on other rigs in that the manifold doesn't heat up until it soaks up actual engine heat and low speed drive ability can be a bit of an issue in cold climates. Those of us in the North aka cold winter areas of the world who don't have heat risers spend some time warming the engine up before we take off. Not only to get the heater working so it will defrost the windshield but so the engine will run a bit smoother.

[dsraven]

if anybody reading this lives in a cold climate and is thinking of taking out the heat riser then bank on having long warm up times on cold days. i have actually seen the throttle plates stuck open, on a stalled engine, due to a lump of ice in the throttle area. moisture in the air on a cold morning, like fog, will actually freeze in the throttle valve area due to the change in temp there because of the air moving faster etc etc. if the engine runs long enough without dying the ice forms a lump there. then the engine dies for sure.

[dsraven]

on the older chevy v8's there is a port runner under the carb that the hot exhaust is directed through to warm the carb. if you look at a set of old original heads thats the center port between the intake ports. if your old car had dual exhaust it would only really be coming out one of the pipes when it was warming up because if the valve worked properly it directed most of the exhaust through the intake port runner to the other cylinder head and out those exhaust pipes.
yup, showing my age again. lol.

[mr48chev]

I'm thinking that all carburetored small blocks had that cross over. I've chipped carbon out of enough of them with a hammer and chisel before.

I am pretty well positive BluDon's Apache has a six in it though. I'm not sure how cold South African winters are. I did look up his home town and it is the red dot on the map on the right side of the page. https://en.wikipedia.org/wiki/Centurion,_Gauteng

Lots of cool stuff around there too.

[BlouDon]

Originally Posted by dsraven

if anybody reading this lives in a cold climate and is thinking of taking out the heat riser then bank on having long warm up times on cold days.

You'll have to define "cold climate" Raven! Where I live, is "cold" compared to the area just 13miles North of where I stay - which in turn is regarded as "cold" compared to an area just 200miles East of where I stay.

Anyway, where I live (1400m / 4600') AMSL we regard it as "cold" when we have a winter morning below 8ºC (46ºF). In the Lesotho mountains (3000m / 10 000') temps can easily go as low as -15ºC / 5ºF.

I can not see that my Apache (while in my custodianship) will require starting at temps below 50ºF.

I have a 74ºC (160ºF) thermostat fitted and I noticed that it is now rather quick to warm up.

Thanks for all the above contributions!!! My conclusion is that if the valve is open, the restriction in exhaust flow is so minimal that as long as it works, it is not worth the trouble of removing it.

[geezer#99]

Where raven lives if he had a cold day like you describe (8C) it would be a fine day to get out for a walk in his shorts and tee shirt. That’s sun tanning weather.

You might consider using a 185 thermostat instead. Motors live longer at closer to 200 degrees.

[BlouDon]

Originally Posted by geezer#99

You might consider using a 185 thermostat instead. Motors live longer at closer to 200 degrees.

Longevity??? This truck will outlast me, my children and grand children - as long as its kept out of the rain.

[geezer#99]

The truck will but the motor won’t.

[dsraven]

Its -17 on my way to work this morning. I zipped my jacket up to half, lol.
Personally I would install a 180 stat, but check the actual engine temp when running on a hot day, likely the 160 stat is fully open and the engine is running hotter anyway. The higher temp stat would keep it running in it's intended range on cooler days. Wont make it warm up any faster if the 160 stat is working proper, just wont warm up any warmer than 160 that's all. Warmer engine runs better, up to a point.

[geezer#99]

That -17 is an iffy temp!
Do I wear my toque or my Oilers cap?
Decisions, decisions!

But seriously the temp isn’t the only factor, you need to be aware of the humidity.
Cool and wet air can effect warm ups more than cool (or cold) and dry.

[mick53]

If it's not broke don't fix it.

[_Ogre]

unless the motor has been rebuilt, chances are the riser passage is plugged off anyway. make sure the flapper is free and open when warmed up. difficult to physically remove as the heat riser gasket is triangular on top and exhaust doughnut on bottom

[geezer#99]

Originally Posted by _Ogre

unless the motor has been rebuilt, chances are the riser passage is plugged off anyway. make sure the flapper is free and open when warmed up. difficult to physically remove as the heat riser gasket is triangular on top and exhaust doughnut on bottom

You do know he has a six banger, don’t you!

[Volfandt]

A little late to the party but what the hey, this is a good topic. That thing-a-ma-jig is actually a pretty ingenious method of getting the long intake runner inline 6 cylinder engine warmed up faster with smoother operation in both warm and cold weather.
In operation the coiled bi-metal spring coupled with the exhaust diverter valve's (called a flapper) counter weight works to keep the flapper in the "open" position which directs "some" or even "most" of the exhaust gases around a cast in air plenum underneath the bottom of the intake runner directly below the carb. What this does is allow the exhaust gas to heat the bottom of the intake manifold so that the in rushing fuel droplets that strike the bottom will be atomized which mixes with the air better which produces a better more efficient fuel/air mixture for better combustion.
Once the bi-metal spring heats up (as well as the entire intake manifold) it begins to unwind and works against the counter weight and exhaust gases to close the flapper cutting of the flow into the heat plenum and directly out the exhaust system which produces more power since it flows better.

I ran a stock 216 with this OEM setup in hot and cold weather and I hardly had any stumbling and/or hesitation after a few minutes of warm up.

I now run a hopped up 235 with dual carbs & dual exhaust with a hardly working preheat setup and not only does warm up take longer in cold weather but it takes 3 times as long for the engine to get up to operating temp and not suffer from stumbling and/or hesitation.

The factory preheat flapper setup is ingenious in it's simple design, operation and maintenance.

An old but entertaining video from back in the day:
https://www.youtube.com/watch?v=IptwXqkzmYA

[BlouDon]

Thanks Volfandt, this makes a lot of sense.

Would be nice if someone could post pics of it....

[Volfandt]

Here's a couple pics of my 216's preheat "flapper" setup.
In the pics you can see the bi-metal spring on one side of the preheat chamber of the exhaust manifold and the counter weight attached to the flapper on the other side.
edited to add a video showing how it operates (he's adding heat to the bi-metal spring with a hair dryer or heat gun.)
https://www.youtube.com/watch?v=5wDV4wIM6Vw

[BlouDon]

Thanks Volfandt

I was trying to get pics of the diverter valve from above when the intake and exhaust manifolds are separated, valve open and closed. :-)