Heat Riser Operation

[MagikDraggin]

Ok....someone please explain to me the proper operation of a heat riser...62 GT Hawk.

I was under the impression that when the motor is cold, the heat riser blocks exhaust gasses from going out the exhaust pipe and diverts them up to aiding in warming the choke/carburetor.

And I thought that once the motor is fully warmed up, the heat riser is supposed to open up and allow the exhaust gasses to flow unimpeded out the tailpipe.

On mine, the heat riser is blocking the exhaust all of the time....though it is working freely and is not bound up. Is that the way it's supposed to be?

Karl




1962 GT Hawk 4sp

[GTtim]

From your description it sounds okay to me. The spring is thermostatic so it will hold the valve open when the engine and the area under the hood is really hot. In my experience the valve almost always closes when the engine is idling except for the hottest days. The valve is mounted off center on the shaft so that when engine rpms increase the valve 'blows' open. You should be able to see this if you rev the engine a little while watching the valve.

Tim K.
'64 R2 GT Hawk

[Rerun]

You are correct in your understanding of how the heat riser is supposed to work. The weight should open the valve, and the bimetallic spring should close it when cold. If it doesn't open when the engine warms up, it will cause the intake manifold to overheat, and can cause vapor lock. The additional back pressure on the exhaust isn't good either.

If it moves freely, but doesn't open when hot, I would be suspect of the bimetallic spring that closes the valve. Is it possible that someone wound the spring a half twist too tightly or installed the spring backwards?

Jim Bradley
'64 Daytona HT "Rerun"

[MagikDraggin]

quote:Originally posted by GTtim

From your description it sounds okay to me. The spring is thermostatic so it will hold the valve open when the engine and the area under the hood is really hot. In my experience the valve almost always closes when the engine is idling except for the hottest days. The valve is mounted off center on the shaft so that when engine rpms increase the valve 'blows' open. You should be able to see this if you rev the engine a little while watching the valve.

Tim K.
'64 R2 GT Hawk

Hmmm, no I didn't try it while revving the motor....I just "assumed", that would open on its own while idling hot. I'll hafta go out and take another look at it.

Thanks much

Karl


1962 GT Hawk 4sp

[GTtim]

It would be good to check the operation while revving the engine. The valve can be installed backwards and then the engine exhaust tends to hold it closed, which isn't a good thing.

Tim K.
'64 R2 GT Hawk

[MagikDraggin]

quote:Originally posted by Rerun

You are correct in your understanding of how the heat riser is supposed to work. The weight should open the valve, and the bimetallic spring should close it when cold. If it doesn't open when the engine warms up, it will cause the intake manifold to overheat, and can cause vapor lock. The additional back pressure on the exhaust isn't good either.

Well, I'm glad to hear I wasn't going totally 'senile'. I am trying to figure out why I got such rotten fuel mileage while driving the Hawk back to Iowa from Ontario. On only one occasion I managed 17mpg and that was with a 35mph tailwind the entire time. All other fillups, the best I could get was between 12.5 and 13.5 mpg. I was told 20-23 is not out of the question...especially with the 4speed.

I checked the choke plate and that is opening up fine when warm...but that heat riser is always closed.....can be moved freely by hand, but always goes to the 'closed' position. As the previous poster mentioned, it should open up under higher rpms....I didn't try that yet.

quote:If it moves freely, but doesn't open when hot, I would be suspect of the bimetallic spring that closes the valve. Is it possible that someone wound the spring a half twist too tightly or installed the spring backwards?

Anything's possible I would suppose. It'd be nice to have a picture to see just how it's supposed to be put together. I have top bid on a shop manual on Ebay.....that should help me out a lot (I hope).

Thanks for the response,

Karl




1962 GT Hawk 4sp

[MagikDraggin]

quote:Originally posted by GTtim

It would be good to check the operation while revving the engine. The valve can be installed backwards and then the engine exhaust tends to hold it closed, which isn't a good thing.

Tim K.
'64 R2 GT Hawk

Ok, went outside and rapped it up a couple times. The butterfly valve does open up when I goose it, but it takes nearly 3000 rpm to get it to open...and once past the initial "surge", and while simply holding a steady rpm, it goes back closed again.

I take it, as the other poster suggested, that the spring is wound too tight. I'll mess with it some more tomorrow.

Karl


1962 GT Hawk 4sp

[GTtim]

Karl, I wouldn't worry too much about the heat riser valve. It sounds like it is operating within the normal range. You can disconnect the spring and let the valve go to full open and wire it in that position. It is really only necessary to have it operational in the coldest of conditions and then only for the brief time when the engine is running and really cold. I don't believe it will affect your mileage much. Other things like ignition timing, carburetor tune, rear axle ratio and driving habits will have much more effect.

Tim K.
'64 R2 GT Hawk

[rockne10]

quote:I have top bid on a shop manual on Ebay

Karl,
With a $12 shipping charge be careful how high you bid. New reprints are available for $48 in hard copy or you can get the manual and both body and chassis catalogs on CD for $24.95.

[MagikDraggin]

quote:Originally posted by GTtim

Karl, I wouldn't worry too much about the heat riser valve. It sounds like it is operating within the normal range. You can disconnect the spring and let the valve go to full open and wire it in that position. It is really only necessary to have it operational in the coldest of conditions and then only for the brief time when the engine is running and really cold. I don't believe it will affect your mileage much. Other things like ignition timing, carburetor tune, rear axle ratio and driving habits will have much more effect.

Tim K.
'64 R2 GT Hawk

I appreciate the comments. As far as I know, the Hawk has a 3.31 final gear. Driving in really cold wx as I was doing at 65-70 mph, I am sure, is not conducive to really 'great' mileage.

Under 'normal' circumstances, I wouldn't even consider doing that again. Summer driving, sure....but winter, with all the snow and ice and wind I had to deal with....the Hawk actually handled it all much better than this 'city slicker' did.

Karl


1962 GT Hawk 4sp

[MagikDraggin]

quote:Originally posted by rockne10

quote:I have top bid on a shop manual on Ebay

Karl,
With a $12 shipping charge be careful how high you bid. New reprints are available for $48 in hard copy or you can get the manual and both body and chassis catalogs on CD for $24.95.

Thanks for the heads up. I noticed the exhorbitant shipping charges (for "media" of all things...probably only cost a couple bucks at most to ship only 1 state away).

I'm not planning on bidding any higher than my opening bid. I saw at a Stude parts supplier where brand new manuals can be had for 48 clams. I wanna actual book and not a "CD".....that way I can drag the thing with me while poking around the vehicle.

I just think it's kinda cool having a car that I can actually work on and not have to have a doctorate in automotive diagnostics and computer programming.

Karl


1962 GT Hawk 4sp

[John Kirchhoff]

One wat to tell if the spring is working ok is to take one of those little propane torches and put heat to the spring. It'll start opening almost immediately afterwards and if it doesn't, you might want to chech further. If it doesn't open up all the way within say 30 seconds (it probably took half that time for the new one I was fiddling with) Jim might be correct in thinking someone wound the spring tighter than it is supposed to be. On the one I have, there's just a little stud sticking out that the end of the spring hook behind so it would be possible to wind it around again and hook it. Good thought Jim.

[studelover]

I just started to clean my heat riser, It was stuck shut and had alot of carbon buiuld up, the looks new and the action after I soaked, cleaned and oiled it is night and day. The proper operation of this unit is very important to older cars, I learned this from my 1940 Plymouth, my plugs were fouling and it was hard to start until I put a kit in and rebuilt my heat riser now the car runs great, if you do not wind the spring too tight, when you turn the weight to open and let it go it should spring back into place. If you clean the opening so the flap can move freely it will not bind I ued a rat tail file.

Studebakers forever!

[blackhawk]

quote:Originally posted by GTtim

Karl, I wouldn't worry too much about the heat riser valve. It sounds like it is operating within the normal range. You can disconnect the spring and let the valve go to full open and wire it in that position. It is really only necessary to have it operational in the coldest of conditions and then only for the brief time when the engine is running and really cold.

Tim - actually you get carburetor icing at relatively warm temperatures (above zero) because the air will hold more moisture. I notice it in the fall before it really gets cold. I would never wire a heat riser in the open position or block the exhaust port through the intake manifold like some have suggested. If you don't get heat to the carb, the engine will stumble and balk. This is not a good thing when you accelerate into the traffic flow. I have also always used as thin a gasket as possible between the carb and intake manifold to facilitate transfer of heat to the carb. I live in a place where it gets cold in winter (Alaska), but much of the northern part of the lower 48 states also gets cold enough in winter to need that heat riser. Studebaker put one on the engine for a reason. Dale

[MagikDraggin]

quote:Originally posted by studelover

I just started to clean my heat riser, It was stuck shut and had alot of carbon buiuld up, the looks new and the action after I soaked, cleaned and oiled it is night and day. The proper operation of this unit is very important to older cars, I learned this from my 1940 Plymouth, my plugs were fouling and it was hard to start until I put a kit in and rebuilt my heat riser now the car runs great, if you do not wind the spring too tight, when you turn the weight to open and let it go it should spring back into place. If you clean the opening so the flap can move freely it will not bind I ued a rat tail file. Studebakers forever!

much better, and the tendancy of the motor to want to "load up" and try to stall under low speed/low rpm lugging (lack of power) is now gone as well.

I am anxious to get the Hawk back out on the highway again (if the weather around here would ever clear up) and see if the gas mileage has improved from the dismal 12-13 mpg I got while driving the car to Iowa after having purchased it.

I don't know for sure if I did it right, but at least it's working now. Once I receive the shop manual, I'll see how the factory recommends it be done.




1962 GT Hawk 4sp