Heat Riser??

[Jeff Ivan]

I took the '51 Ply for a short cruise today. The heat riser started rattling and flapping like crazy, and the temp gauge started to climb and the weather was not too hot. I think the spring coil must have broke. My stupid question is- What position should the heat riser be in when it is in the open (warmed up) position? I want to clamp it in the open (warmed up) position temporarily, since I don't drive it much in the cold weather months anyways. Is the open position towards the front of the car when standing on the right (passenger) side) clockwise position facing exhaust manifold? BTW I have NEVER had a reaction to a bee or hornet sting in my 49 years on earth, and have been stung many times, yet today when I got back from my ride and was doing a M-I-C-K-E-Y M-O-U-S-E certified repair to my muffler/tailpipe, I got stung and my finger swelled up like a boy in puberty with a Playboy magazine. I followed first aid procedure ,immediately said "#@$!&*^%$#@#$** "and removed the stinger, and held an ice cold beer on my hand. Then I forced myself to consume the beer. Swelling went down in about a half hour, removed the rest of the stinger, then all was OK, then I started to try to figure out the heat riser thing as it got dark outside. Another question? Why did my status on this forum recently change from 'Junior' to 'Member'? Does it have to do with my number of postings here? Just wondering:confused:

[cwcars88]

I believe when the riser spring gets hot it will relacks and let the counter weight fall to the down position, which is open.

[55 Fargo]

Jeff, I noticed the same thing when I got a bee sting a few years ago, it was also on the hand. Too bad you didn't have the beer before hand, they say urine will ease the sting and bring down the inflammation........LOL........Rock

[55 Fargo]

Greg G. Quoted this on an archived thread, should answer your question.

Rotated clockwise closes the heat riser. That is the flap wil be in aposition to NOT Direct exhaust gas into the intake heat chamber. the at rest position is the open position, the bimetalic spring shoud turn it clockwise against the counter weight when the engine is up to temp. A stuck heat riser may cause higher under hood temps as there are two cast iron masses exposed to exhaust gas temperature, but is shouldn't have much of an effect on engine coolant temp. Have you checked the actual temp of the coolant with a reliable thermometer? A small cooking thermometer stuck into the radiator fill will indicate colat temp. This will be slightly cooler than the sensor temp as it is pretty close to where the coolant flow is the hottest. but your gauge may be off. Have you checked your radiator flow? High temp speed usually indicated a coolant flow situation, is your stat opeing all the way? What happens when you run with out a stat?

[BobT-47P15]

Re: your status title - it IS influenced by the number of posts made.

[eric wissing]

Jeff, check to make sure the shaft is actually turning the flap. The weight can come loose and be doing nothing. Eric

[grey beard]

Hi Jeff,

There's been a whole load of "old bunny" about heat risers going around. Please don't let anyone stuff your boots on this subject - hardly worth it.

First off, your heat riser will in no way affect the temperature of your water jacket unless there are other major and severe problems. The only reason for a heat riser on any vehicle is to keep the carburetor from "icing" up in damp wearther when the amhient temperatures are between 28 and 36 degrees farenheit. This icing is more correctly termed frost, that forms in damp weather from the cooling action of the carb venturi as it pulls air into the engine - the moist air on the outside of the carb body actually gets cold enough to frost up, and this will bring any engine to a stop.

Used to drive an old school bus that would stall out every fall morning on the same hill half a mile from the house. You could jump out and open the hood and see the frost on the carb body. Let her sit two minutes and it disappears and you're good to go again, till the engine gets up enough heat to warm up the carburetor.

Now there are folks around who will tell you that the heat riser affects performance, gas mileage and probably sex life. They do not affect engine idle, or acceleration, or oher drivability issues. This is sheer malarky.

Heat risers only ever do any helping during the first four or five minutes of engine running in cool damp climates. If you live in Arizona, pitch it in the trash. They are completely useless and unnecessary in summertime driving and in temperatures below twenty degrees, because the air is drier and the frost phenomenum does not occur. During the sixties, many car makers accomplished the same objective with an air flap in the air cleaner nose and a paper hose down to the exhaust manifold - just takes a tad of heat on those nasty, damp mornings to keep things from icing up - nothing more,nothing less.

Mine is blocked fully forward and will never cause a problem. If one ever siezes up in the "heat" position, the result will be that the carburetor will be forced to run much hotter than normal. This WILL affect gas mileage and performance.

The thing to remember about heat risers is that they must be in the forward or warm position when the engine is warmed up. If they are not, you will definitely experience drivability problems. JMHO:)

[55 Fargo]

Dave, thanks for the explanantion n the heat riser's function. Got me thinking, I had a 79 Furd Fairmont some years ago, on the highway in Winter when the outside temp was just around freezing it would ice up, as the heat riser wasn't working right. But when it was colder out, which in Winter in Manitoba it usually is, there was no icing problems, only around the freezing point, especially if there was alot of moisture in the air. On my 47 Chrysler, I am sure the heatriser is stuck in the cold position, allowing hot air up and around the carb. I do plan on eliminating the heatriser and welding a plate to allow the exhaust to exit directly out, for 2 reasons, mine is a summer car, would never be winter or cold damp sloppy weahter driven either............Fred

[Jerry Roberts]

Greg G. Quoted this on an archived thread, should answer your question.

" Rotated clockwise closes the heat riser. That is the flap wil be in a position to NOT Direct exhaust gas into the intake heat chamber. The at rest position is the open position, the bimetalic spring shoud turn it clockwise against the counter weight when the engine is up to temp. "

That is the best description of the heat riser operation that I have ever read . It makes it easy to understand .

[RobertKB]

Dave and Fred, thanks for the easily understoodon info on heat risers. Always knew they had a function but you both articulated it very well. Basically, if it's stuck you want it stuck in the forward (clockwise) position. Unfortunately, most cars that have sat around for a while and have the riser rusted so it won't turn will have it in the other position.

[Don Coatney]

the moist air on the outside of the carb body actually gets cold enough to frost up, and this will bring any engine to a stop.

Dave;

It is not the frost on the outside of the carburetor that brings the engine to a halt. It is the frost on the inside of the carburetor that restricts air flow and chokes the engine causing it to stall due to a rich mixture. Gas line antifreeze will prevent this as there is alcohol in the antifreeze that chemically bonds with water and lowers the freezing point.

[grey beard]

You may wish to consider that proposition a little - carb venturi freezing up where the air flow is increased, causing frost both inside and outside. You are correct that it is the frost on the inside that does the dastardly things, and that the frost on the outside is just an indication of what is going on inside, but I fear you will have little success remedying that problem with dry gas or gasline antifreeze - which today is incorporated into all gasolines, by the bye, so we don't need those little cans anymore. It's not the fuel that does the freezing, it is the carb airhorn body, itself. The moisture in the air freezes on contact with the colder metal. The fuel, itself is not able to atomize proerly in the presence of the frost that forms.

I'm betting that Southern folks see very little of this phenomenom. It can happen here in PA only a few days each year - spring and fall, when the temps are just right and the humidity is high. Bet it hardly ever happens in Tennessee, huh?

[Jeff Ivan]

Kinda makes me wonder what is in the 'STA-BIL' fuel stabilizer besides the alcoholic gas line anti freeze, or "dry gas" as it is called here in Western PA. The stuff does seem to work tho. I have brought this up here before and had some disagree with me, but I still am convinced that the gasoline sold in this region only has a shelf life of 2-3 months with no stabilizer added. My 51 Plymouth sat for a lot of this season, and I put almost 100 miles on it this weekend. It did not run quite right even with fresh spark plugs until I topped off the tank with 4 gallons of fresh fuel today ( all I could squeeze in), but still ran better than with no 'STA-BIL' added. I have myself convinced the gas is mostly at fault here because I do the majority of my grass cutting with a diesel tractor, and the gas mower used for trimming seems to run worse and stall out more easily in thick grass as the summer drags on and the 5 gallon can of gas I filled in April or May gets used up. If I had 1/2 of a brain I would add the stabilizer to the can of lawnmower gas as soon as I buy it, and not just put it in the '51. Also today I drove the Plymouth about 35 miles and the heat riser was not making noise anymore, and the temp gauge seemed to behave. Must be the new plugs, fresh oil, and black wax buffed on to the barely presentable paint job. She must have felt a little neglected this summer.

[greg g]

Way back when, I used to race a 75 Honda Civic on the ice inthe winter at temperatures that promoted the formation of a 12 inch layer of ice on a large lake. this particular car would run a warm up and practice and a 10 lap race without a problem. When it came time for the 20 lap feature race it would always die on the 12th or 13th lap, Every weekend regardless of the temperature and other atmospheric conditions. After pulling off the course and waiting till the other finished the race it would always start up and run defiantly back to the pits and back up onto the trailer (little b@$t@rd). I ran the paper air filter in the stock housing without the hose to the exhaust manifold.......Then it hit me why it woud stall then restart and run fine. the carb was freezing up. Rather than running the hose to the ehaust manifold, the hose was missing cause the sheetmetal heat collector had long since oxidized back to its source. So I got some aluminum flex ducting from the hardware store, and pulled air from the space in the foot well next to the heater. Problem solved, finished and won many class features and took class championship for the final three years of the cars life. So carbs do freeze up, why do airplanes have carb heaters???? To keep them and the plane they are atteched to from falling from the sky ( guess it can get cold up there regardless of season)

Moral, my heat riser is welded in the closed (exhaust bypassing the intake) as I drive usually in warm temps. I have had the car out on a couple of 30 to 40 degree mornings and evenings, and have noticed it likes the choke open wider and for longer than it does at warmer temps. It does stumble a bit till fully warmed. But for normal warm weather operation, my opinion is it is better for it to be closed (clockwise) then open.