Thanks for the video. I finally got my heat riser freed up on my 50 216, and still need to get a spring on it which I think is on the opposite side from what yours showed,. But after watching the video, I thought I had mine set in the closed position, but now I think I have it in the open position which is heating the intake all the time. It operates opposite of what I was thinking, so thanks for clearing it up.
Last edited by 4100 Fire Truck; 08/10/201812:55 PM.
If you need it to work at times but have high air temperature frequently, the amount of heat transfer to the intake manifold casting can be reduced by inserting a flat plate in between the 2 to limit the surface area contacted by the exhaust gas.
A mid 1930's Buick straight 8 I worked on a long time ago had a manually-controlled heat riser valve with linkage on the steering column. Lots of small aircraft engines have the same sort of system to prevent carburetor icing under certain flight conditions. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
When people think of an engine running properly because it has warmed up, it is the intake manifold that is actually the part that makes the car "feel" warm. You need to have a hot spot under the carburetor to vaporize any atomized fuel that falls out of the airstream when it hits the intake manifold floor. Liquid gasoline will run along the bottom of the intake manifold and into the cylinders to end up washing oil off the cylinder walls and diluting the engine oil Not having a hot spot will also give the car a lean bog when the engine is not fully warm. I do not recommend disabling the manifold heat control system even if you live in Furnace Creek. See Engine Wear.
Manifold vacuum helps to vaporize atomized gasoline in the intake manifold and absorbs heat in the process. Without a continuous supply of exhaust heat, the intake manifold will become very cold. If you have a problem with carburetor percolation, you are far better off adding insulation (like a phenoloic spacer) under the carburetor to help keep it cool. See Intake Manifold Heat.
When people think of an engine running properly because it has warmed up, it is the intake manifold that is actually the part that makes the car "feel" warm. You need to have a hot spot under the carburetor to vaporize any atomized fuel that falls out of the airstream when it hits the intake manifold floor. Liquid gasoline will run along the bottom of the intake manifold and into the cylinders to end up washing oil off the cylinder walls and diluting the engine oil Not having a hot spot will also give the car a lean bog when the engine is not fully warm. I do not recommend disabling the manifold heat control system even if you live in Furnace Creek. See Engine Wear.
Manifold vacuum helps to vaporize atomized gasoline in the intake manifold and absorbs heat in the process. Without a continuous supply of exhaust heat, the intake manifold will become very cold. If you have a problem with carburetor percolation, you are far better off adding insulation (like a phenoloic spacer) under the carburetor to help keep it cool. See Intake Manifold Heat.
Fraso, I live in SC where temperature dips below 30 degrees only a few times each winter. My plan is to keep the flap in the manifold in the closed position so that the MAJORITY of the exhaust is diverted down. The exhaust can still get through to warm the intake because the flap really doesn’t come anywhere close to making a tight seal.
I spoke to Tom Langdon about this subject. He sells a warming device for people who have converted to headers. His device uses circulating hot radiator coolant to warm the intake. It takes several minutes for any engine to get warm enough to open the thermostat, so at best his device doesn’t add heat for 3-4 minutes. He said that living in a warm climate like SC, if I keep my flap in the closed position and just wait a minute or two, the heat would build and I’d be fine. That’s my plan. Northern folks need to figure out how to make their heat risers work.
If you're willing to wait a few minutes for the coolant to get hot, then wait awhile more for that heat to transfer itself through the intake to actually begin warming the fuel mixture, you've got more patience than most of us. 100-something degree water VS 1,000+ degree exhaust gas- - - - -which one is going to do a better job of keeping the fuel vaporized? Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Jerry, You don’t mention that both the headers and the factory manifold will get HOT no matter what heat riser you use. That heat is essentially directly below the intake and will warm the intake by ? ? ? is CONVECTION the right word? So I’m sorta curious as to what the IDEAL temperature for an inline intake would be? I seem to think the R&D department decided that “too hot” was bad, so they designed the heat riser to close so it would limit heat exchange after the engine was up to temp.
Good convo. At what temp is it heated enough? I dunno. My 216 has a working heat flapper with the bi-metal spring installed correctly per the shop manual. I know that within a minute the intake manifold is getting pretty hot to the touch and after it's run awhile the intake almost feels as hot as the exhaust manifold and the flapper is closed i.e. directing exhaust gases straight out the pipe and not around the intake plenum. My mpg isn't great, around 13 mpg, but considering the age of the bottom end (est over 120k miles) the 216 runs real good. No hessitation, power to pull hills in high gear and it can hit 65+ in the rare instances when I have to pass a slower vehicle. It runs good in all 4 seasons so the manifold getting hot seems to be a benefit year round. Sometimes with the manifold heated up I can still see some condensation around the base of the carb.....
I believe it was Dads50 that posts a video showing how to use a hair dryer or heat gun to heat up the spring to see if the flapper works. It's a good test.
I have never seen an automobile manufacturer choose to use coolant as an intake manifold heat source. That alone should speak volumes about what factory R&D people think of the idea. Even water-heated automatic chokes were tried for a short time, and promptly abandoned in favor of electric choke heaters because the chokes couldn't be released fast enough to meet federal exhaust emission standards. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
If you're willing to wait a few minutes for the coolant to get hot, then wait awhile more for that heat to transfer itself through the intake to actually begin warming the fuel mixture, you've got more patience than most of us. 100-something degree water VS 1,000+ degree exhaust gas- - - - -which one is going to do a better job of keeping the fuel vaporized?
The some atomized fuel (ie, very small liquid fuel droplets) will vaporize (ie, become gaseous fuel) all by itself with high manifold vacuum and some will remain atomized until vaporized in the combustion chamber..
While it does take longer for water to reach operating temperature, the entire manifold doesn't have become 195° for the engine to feel warm. Even when the coolant is fully cold, it still has some heat in it and, as the engine runs, it continues to gain heat. The important thing is that the area directly under the carburetor is warm enough to vaporize most of the fuel that falls out of the airstream so that it doesn't form a puddle on the floor of the intake manifold.
Originally Posted by Lugnutz
Jerry, You don’t mention that both the headers and the factory manifold will get HOT no matter what heat riser you use. That heat is essentially directly below the intake and will warm the intake by ? ? ? is CONVECTION the right word? So I’m sorta curious as to what the IDEAL temperature for an inline intake would be? I seem to think the R&D department decided that “too hot” was bad, so they designed the heat riser to close so it would limit heat exchange after the engine was up to temp.
Without a manifold heat control system (ie, header-equipped engines), the intake manifold will warm up through CONDUCTION from the cylinder head. The intake manifold's temperature will obviously decrease from the cylinder head to the carburetor because of air flow and vaporizing gasoline.
The temperature of the intake manifold just needs to be hotter than the boiling point of the majority of components of gasoline. Light components (like ethanol) have very low boiling points (which cause percolation in the carburetor and vapor lock in the fuel pump) and heavier components have much higher boiling points. The heaviest fractions of gasoline evaporate in the 300-400°F range so having a 200°F hot spot would not be too hot. See Vapor Lock
