Heat Risers? . . . . . . Naaaahhhhhh!

[grey beard]

IMHO, heat risers are highly over-rated and even more highly misunderstood. The real purpose for adding them when this stuff was manufactured was to keep the carburetors from icing up on damp cold mornings in fall and spring weather in colder climates. You Calofornia fellows could throw them away and you would never miss them.

For those of you who feel they are teddibbbbbly important, consider thiis; Heat risers went the way of the outhouse in the early to mid fifties. If they are so critical to engine warmup and performance, how do we live without them today? Ford used a hot air duct from the exhaust manifold up to the air cleaner for the same reason - to keep carburetor icing from occurring on cold damp mornings. This is not a aproblem below freezing or in warm weather.

If you live in an area like I do - southeast PA - and the winters get pretty cold, just let it run two or three minutes before you hit the road. Once the exhaust manifold warms up, even a perfectly operating heat riser would already be open anyhow, and is just along for the ride. In no way will a heat riser change your long range economy or your over-the-road performance. Why, nearly half of the guys on these forums have headers or split manifolds - all of which run without them. If yuou are still not convinced, larger trucks and tractors were manufactured without them, as well.

I read threads about people worrying about issues like fuel mileage and performance - and read other threads by folks who attribute all their ills to poorly operating heat risers. Likely as not, they cause relational problems with mother-in-laws, as well. This thinking is simply fallacious. Even a brand new, pefectly functioning heat riser is wide open after three or four minutes of engine operation - or it is not workking peoperly.

Having said all that, I blocked mine open rather than go to the work of splitting the manifolds to fix a broken spring. Just move it in the clockwise direction until the counter weight is nearly horizontal, or until it won't move anymore - and bend it inward till it hits the manifold and stays put in that position, and you will never need it again.

A good working, high temp thermostat will get your engine operating temperature up to normal much faster than all the heat risers in the world. If you REALLY want something to worry about, make sure your heat riser is not stuck in the CLOSED - or counter clockwise - position. Very few things will affect overall engine pefformance and life as quickly as a stuck closed heat riser, for you are literally cooking the carburetor all the time the engine is warmed up. Now if your heat riser is stuck closed, and your thermostat is stuck open, you have a recipe for short engine life, lousy pefformance and terrible gas mileage. There's something we could all do well to worry about.

[Plymouthy Adams]

A properly functioning heat riser brings the engine up to temp in faster smoother manner enabling the fuel to atomize better and overall cold operation be on the decline saving you fuel in the long run. As for doing away with them in the 50's...you must have stayed in the outhouse while the plumbing was changed in your house as they were alive and well even into the 80's

As for Ford the heat tube you see is for one reason..diverts gasses up to the bi-metal in the choke housing to accelerate the opening of the choke butterfly. A functioning heat riser diverts gases but if functional and free will still be blown open on acceleration...an engine under acceleration does not utilize the choke circuits and therefore that mixture is not in the mix so to speak. Can you live without it yes...is it worth fixing...your call...the real nix is the thing closing and getting stuck in that position..back pressure is now the problem, , stumbling on acceleration and increase in engine temp. Leaving it opens lengthens the time the engine takes to get to temp wasting fuel and sooting you plugs..

[Merle Coggins]

Open? Closed? I seem to be getting confussed. You guys seem to be refering to the "Closed" position as when the flap is in the vertical position, allowing exhaust gasses to circulate up around the intake to heat it up. I was always under the impression that this helps to atomize the fuel when cold for better cold engine performance. To me this would be the "Open" position.

And what you are calling the "Open" position would have the flap closing off the gasses to the intake manifold. Wouldn't this be the "Closed" position?

Dave mentiones locking his "Open" rather than "spliting the manifolds to replace a broken spring". Maybe his is different than mine, but I can pull the counterweight off and replace the spring without disturbing the manifolds. Mine was stuck in what I call the "Closed" position when I got teh truck, and the manifolds were off teh engine and split already. With a little heat I got the flap freed up again. The spring was also broken, which was replaced with new.

So am I reading these posts wrong, or am I confussed as to which way is "Open" and which way is "Closed"?

Merle

[Plymouthy Adams]

When I refer to CLOSED, the butterfly is blocking exhaust and diverting..

When I refer to OPEN the butterfly is NOT blocking exhaust...

These things are necessary for proper opertion of choke especially in the later V engines as the choke pull off was mounted into a pocket cast in the the manifold and relied upon engine heat to work..the heat riser when cold does divert gasses up and over to the other manifold by way of passage under the choke oven and through the intake under the carb..heating the choke and manifold to promote fuel atomization...

With the newer computer controlled cars the rich cold start is maintaned by the computer through temp sender feedback circuits..two on new cars..and in the era before digital when analog, the cold start valve enriched by mean of a temp sender simular to the one used to report engine temp to the guage on your dash..should you be lucky enough to even have a guage.

[Merle Coggins]

OK, I guess that makes sense too. I always though of it as "Open" to the intake manifold, or "Closed" to the intake manifold. I guess it's just a matter of perspective.

[Guest Nile Limbaugh]

Mine was so frozen in place, and closed (vertical) that nothing short of dynamite was going to move it. So I got the manifold apart and whacked the plate off with a cold chisel. Sure, it takes a bit longer to warm up, but down here it just ain't a problem.

[TodFitch]

Most cars on the road today have fuel injection with relatively high pressure in the fuel lines. And the pump is usually in the tank pushing rather than pulling the fuel. So vapor lock is not the a problem with an "everyday car" nowadays like it was back in the day of carburetors. So the oil companies are often making their fuel more volatile than they once did.

For that reason the heat riser probably made more difference "way back when" than it does now. On the other hand, because of the gasoline available vapor lock in the older cars is more of problem now than when the cars were new.

All that said, from personal experience -- at least on my car -- I think the heat riser helps on cold start drivability.

[grey beard]

All Y"all have to admit one thing, no matter HOW you freel ahout heat risers . . . . . . we did stir a mite of controversy there for a minute or three.

LOL

[Young Ed]

I was kinda wondering myself what all the californians were talking about. Now here in MN its probably a little more helpful. The one in my truck doesn't use a spring-you were supposed to change it yourself. Its set to summer probably permanently now. My coupes is free but springless. Neither run well until they are warmed up a couple minutes. Who sells the springs? I believe thats all my coupe needs.

[TodFitch]

. . . Who sells the springs? I believe thats all my coupe needs.

Antique Auto Parts Cellar

PO Box 3 (6 Chauncy Street)

Weymouth , MA 02190

Telephone: +1.781.335.1579

Fax: +1.781.335.1925

email: Thecellar@then-now.com

http://www.then-now.com/

[Merle Coggins]

I got my spring from Andy Bernbaum. www.oldmoparts.com

[T.Tom Meshingear]

As gasoline molecules are sucked through the venturi of a carburetor they mix with air as they travel through the manifold. The droplets that are too heavy (not enough air) fall to the bottom of the manifold where the "Hot Spot" is and are then turned into vapor. Gasoline does not burn - gasoline vapor does. If the droplets were not heated up they would eventually find their way into the engine, dilute the oil, cause excessive wear and decrease fuel mileage.

Ever notice that the hot spot is always right under the carb - that's where the droplets fall. Fuel injected engines don't need a heat riser because the injector does the vaporization.

Tom

[teardrop puller]

I have a langdon's Offy intake and cast iron headers. I bought the heat plate that puts hot water in the bottom of the intake manifold. If you have headers there is absolutely no heat from the exhaust manifold, If you have a regular exhaust manifold then you still get plenty of heat passed to the intake to keep the gas vapor as a vapor. On my jeep the Offy intake came with a water inlet, the Offy for the Plymouth comes as if you are using it on a stock exhaust manifold. Probably in the old days most people just spilt their manifold thus they still got heat to the intake.

You need some kind of heat to keep the gas in a vapor. Better gas mileage with heat I think.

Here is the web page for the heat plate.

http://www.stoveboltengineco.com/acartpro/category.asp?catcode=21

kai

[Rodney Bullock]

On my 1960's cars I have noticed the heatriser was moved to the exhaust system at the connection to the manifold the counter weight is a spacer between the pipe and the manifold connection. When I had my spacer connected to my bird it would start on the first try everytime. after I obmitted it listnening to my friends It never started that way again. The Studebaker I am working on now has the heat riser on the exhaust pipe as well so it did continue well into the 70's and 80's My 1940 Plymouth runs and picks up speed better then better then it did before I repaired it, my starting problem was infact due to the heatriser not operating correctly once I clean the plugs and reinstalled the plugs it starts on the first or second try. The incorrect installation caused the plugs to foul, now it's back to normal. that's why I have an easy start situation now.When these systems are right the car will work very well because eng. designed it:rolleyes:

[De Soto Frank]

On flathead MoPars with the Sisson Electro-magnetic Automatic choke, a functioning heat riser is important to engine warm-up.

Without the heat riser, the intake manifold takes longer to warm-up, while the exhaust manifold heats fairly quickly ( with or without the riser). Since the Choke thermostat/magnet is parked on top of the exhaust manifold, the choke spring heats-up and relaxes as the exhaust warms-up, thus allowing the choke to open due to gravity acting on the choke linkage.

W/o the heat riser, the choke opens when it normally does, but the mixture is too lean for the still-cold intake, and we get a stumble or flat-spot until we step harder on the gas and the accelerator pump richens the mixture momentarily.

My '41 De Soto (riser missing its spring) is a classic example of this: runs and drives great at dead-cold/full-choke, and also when fully -warm... but in-between ( after about one minute of operation), it begins to stumble on acceleration, and I have to goose the throttle to over-come the leaning-out, until it's warm.

As long as I'm pulling a constant speed or accelerating very gently, it does not buck or spit during warm-up...

I am fairly satisfied this is due to the in-active heat riser: one day, I tied-it closed and drove it, and the engine ran much better during warm-up: almost no stumble at all... I was so thrilled with the improvement that I headed for the highway, on my way to work. I had forgotten that I had tied the heat-riser closed... until I'd gone about 5 miles, and noticed that water temp was running above normal... so I pulled-off, released the heat riser, and continued at normal temps.

I still haven't gotten around to fixing my heat riser, but I am firmly convinced of its value in promoting driveability while the engine is warming-up.

I think for those guys whose MoPars have a manual choke, the heat riser may seem less effective, probably due to our management of the manual choke: we keep the choke pulled-out enough for smooth running, as needed, until the engine is warm.

My 1960 Chrysler, with its "modern" RB-383 Wedge-motor still has a heat riser to the intake...

When heat risers were first developed, in the late Teens and early Twenties, apparently the gasolines then were really low in octane and needed all the help they could get to vaporize...

Chrysler's engineering dept wouldn't have loaded their vehicles down with unecessary stuff back in the days when Zeder, Breer, and Skelton were calling the square-dance...

[Dryerventwizard]

My heat riser is free goes back and fourth but did not have a spring so I bought one. I cant figure out how it works. There is no picture in my shop manual or online.  But from what I hear maybe it does not matter. Because  I live in California.  So maybe it is ok to just leave it free then.

[Sniper]

Depend on where in California you live.  I spent 10 years in San Diego and I never needed the heat riser.

 

But If I had lived in Alpine I would need it.

 

https://p15-d24.com/page/p15d24/tech/heat_riser_adviser.html/

 

 

[Dryerventwizard]

In the valley by modesto ca

[TodFitch]

33 minutes ago, Dryerventwizard said:

In the valley by modesto ca

 

You might find it helps on cool damp winter mornings. When I lived in Sunnyvale, a bit milder climate than in the Central Valley, I found that if the ambient temperature was in the high 30s or low 40s and the humidity was up that there was some improvement in drivability when engine was cold. But it won't be a big difference and if you let the engine compartment warm up a little before driving it will be even less of a difference.

[falconvan]

Mine was froze solid so I cut the flapper off and put a block off plate between the manifolds. I figure if you put headers on they get eliminated so it cant be any different.

[Dryerventwizard]

Can you explain  how to do that please. I was thinking of doing that my self just so it does not get stuck and cause problems. 

[lepic56]

On 6/15/2020 at 11:29 PM, Sniper said:

Depend on where in California you live.  I spent 10 years in San Diego and I never needed the heat riser.

 

But If I had lived in Alpine I would need it.

 

https://p15-d24.com/page/p15d24/tech/heat_riser_adviser.html/

 

 

Wow !!! Sniper,,    Great article on ''How to repair a heat riser valve,,''   almost a ''must to read ''  at least for Knowledge about our car's Fuel/exhaust system.   ? I found it easier if I removed my R/H wheel & inner fender, the valve is right there..

[Sniper]

I'd like to claim credit, but all I did was find someone else's work and posted the link.  Hope it helps.

 

Where I live now I pretty much do not need a heat riser valve either.  But I have one and it works.  I have made a habit of turning the valve by hand anytime I happen to be under the hood, if it starts to get tight a can of MoPar heat riser solvent, pn 43138039AE, takes care of it.

 

[Dryerventwizard]

Mine turns fine but which way do u turn it when the engine is running. 

[lepic56]

5 hours ago, Dryerventwizard said:

Mine turns fine but which way do u turn it when the engine is running. 

clockwise when running

, I belive.